SIST EN IEC 60404-18:2025

SLOVENSKI STANDARD
01-junij-2025
Magnetni materiali - 18. del: Materiali za permanentne (trdomagnetne) magnete -
Metode merjenja magnetnih lastnosti v odprtem magnetnem krogu z uporabo
superprevodnega magneta (IEC 60404-18:2025)
Magnetic materials - Part 18: Permanent magnet (magnetically hard) materials -
Methods of measurement of the magnetic properties in an open magnetic circuit using a
superconducting magnet (IEC 60404-18:2025)
Magnetische Werkstoffe - Teil 18: Permanentmagnetische (magnetisch harte)
Werkstoffe - Verfahren zur Messung der magnetischen Eigenschaften in einem offenen
Magnetkreis mit Hilfe eines supraleitenden Magneten (IEC 60404-18:2025)
Matériaux magnétiques - Partie 18: Matériaux (magnétiques durs) pour aimants
permanents - Méthodes de mesure des propriétés magnétiques en circuit magnétique
ouvert à l'aide d'un aimant supraconducteur (IEC 60404-18:2025)
Ta slovenski standard je istoveten z: EN IEC 60404-18:2025
ICS:
17.220.20 Merjenje električnih in Measurement of electrical
magnetnih veličin and magnetic quantities
29.030 Magnetni materiali Magnetic materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60404-18

NORME EUROPÉENNE
EUROPÄISCHE NORM April 2025
ICS 17.220.20; 29.030
English Version
Magnetic materials - Part 18: Permanent magnet (magnetically
hard) materials - Methods of measurement of the magnetic
properties in an open magnetic circuit using a superconducting
magnet
(IEC 60404-18:2025)
Matériaux magnétiques - Partie 18: Matériaux (magnétiques Magnetische Werkstoffe - Teil 18: Permanentmagnetische
durs) pour aimants permanents - Méthodes de mesure des (magnetisch harte) Werkstoffe - Verfahren zur Messung der
propriétés magnétiques en circuit magnétique ouvert à magnetischen Eigenschaften in einem offenen Magnetkreis
l'aide d'un aimant supraconducteur mit Hilfe eines supraleitenden Magneten
(IEC 60404-18:2025) (IEC 60404-18:2025)
This European Standard was approved by CENELEC on 2025-03-27. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
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Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60404-18:2025 E

European foreword
The text of document 68/768/CDV, future edition 1 of IEC 60404-18, prepared by TC 68 "Magnetic
alloys and steels" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-04-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-04-30
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60404-18:2025 was approved by CENELEC as a European
Standard without any modification.
Annex ZA
(normative)
Normative references to international publications with their
corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-121 1998 International Electrotechnical Vocabulary (IEV) - Part - -
121: Electromagnetism
IEC 60050-151 - International Electrotechnical Vocabulary (IEV)- Part 151: - -
Electrical and magnetic devices
IEC 60050-221 1990 International Electrotechnical Vocabulary (IEV) -- Chapter - -
221: Magnetic materials and components
IEC 60404-5 - Magnetic materials - Part 5: Permanent magnet EN 60404-5 -
(magnetically hard) materials - Methods of measurement
of magnetic properties
IEC 60404-8-1 - Magnetic materials - Part 8-1: Specifications for individual EN IEC 60404-8-1 -
materials - Permanent magnet (magnetically hard)
materials
IEC 60404-18 ®
Edition 1.0 2025-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 18: Permanent magnet (magnetically hard) materials – Methods of

measurement of the magnetic properties in an open magnetic circuit using a

superconducting magnet
Matériaux magnétiques –
Partie 18: Matériaux (magnétiques durs) pour aimants permanents – Méthodes

de mesure des propriétés magnétiques en circuit magnétique ouvert à l'aide

d'un aimant supraconducteur
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20, 29.030 ISBN 978-2-8327-0157-7

– 2 – IEC 60404-18:2025 © IEC 2025
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references. 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 9
4 General principle . 9
4.1 Principle of the method . 9
4.2 Superconducting magnet (SCM) . 11
4.3 Magnetic field strength sensor (H sensor) . 11
4.4 Magnetic dipole moment detection coil (M coil) . 11
4.5 Specimen rod and moving device . 12
4.6 Measuring devices and data processing device . 12
5 Test specimen . 13
6 Preparation of measurement . 14
6.1 Measurement of volume of the test specimen . 14
6.2 Initial magnetization of the test specimen to saturation . 14
7 Determination of magnetic polarization . 14
7.1 Measurement of the magnetic dipole moment . 14
7.1.1 SCM-VSM method. 14
7.1.2 SCM-extraction method . 15
7.2 Determination of magnetic polarization . 15
8 Measurement of magnetic field . 15
9 Calibration of the magnetic dipole moment detection coil (M coil) . 16
10 Determination of demagnetization curve . 16
11 Demagnetizing field correction . 17
11.1 General . 17
11.2 Method A: Method using a demagnetizing factor determined by the shape of
the test specimen only . 17
11.3 Method B: Method using a demagnetizing factor determined by the shape
and the magnetic susceptibility of the test specimen . 18
11.4 Method C: Method using an inverse analysis considering the spatial
distribution of the self-demagnetizing field strength in the test specimen . 18
12 Determination of principal magnetic properties . 19
12.1 Remanent magnetic polarization J . 19
r
12.2 Maximum energy product (BH) . 19
max
12.3 Coercivity (H and H ) . 19
cJ cB
13 Reproducibility of the measurements . 19
14 Test report. 20
Annex A (informative) Demagnetizing field correction . 21
Annex B (informative) Details of the demagnetizing field correction . 23
B.1 General . 23
B.2 Symbols . 23

IEC 60404-18:2025 © IEC 2025 – 3 –
B.3 Method using a demagnetizing factor determined by the shape and magnetic
susceptibility of the test specimen (Method B) . 24
B.4 Method using an inverse analysis considering the spatial distribution of the
self-demagnetizing field strength in the test specimen (Method C) . 26
Annex C (informative) VSM measurement of the test specimen at elevated
temperatures . 30
Annex D (informative) Effect of test specimen dimensions on the magnetic properties . 31
Annex E (informative) Comparison of the magnetic properties measured with a
superconducting VSM and a permeameter . 32
Bibliography . 34

Figure 1 – Demagnetization curve J(H) . 8
Figure 2 – Schematic diagrams of the test apparatus . 10
Figure 3 – Schematic diagrams of the first order gradiometer coil . 12
Figure A.1 – Schematic diagram of the demagnetizing field correction . 21
Figure A.2 – Comparison of the demagnetization curves corrected using demagnetizing
field correction Method A, Method B and Method C . 22
Figure B.1 – Axes of a cuboid magnet . 24
Figure B.2 – Conceptual diagram of the procedure of Method C . 27
Figure B.3 – Flowchart of the procedure of Method C . 28
Figure C.1 – Schematic diagram of the heating unit equipped in a test apparatus . 30
Figure D.1 – Effects of test specimen dimensions on magnetic properties [B , H , H
r cJ cB
and (BH) ] of Nd-Fe-B sintered and hot deformed magnets with different average
max
grain sizes . 31
Figure E.1 – Comparison of demagnetization curves measured with a permeameter
and a superconducting VSM . 33

Table A.1 – Features of the demagnetizing field correction methods in comparison with
Method B . 21
Table E.1 – Comparison of magnetic properties measured with a permeameter and a
superconducting VSM . 32

– 4 – IEC 60404-18:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 18: Permanent magnet (magnetically hard) materials –
Methods of measurement of the magnetic properties in
an open magnetic circuit using a superconducting magnet

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60404-18 has been prepared by IEC technical committee 68: Magnetic alloys and steels.
It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
68/768/CDV 68/775/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

IEC 60404-18:2025 © IEC 2025 – 5 –
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 60404 series, published under the general title Magnetic materials,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 6 – IEC 60404-18:2025 © IEC 2025
INTRODUCTION
High-performance permanent magnet materials with high coercivity, for example Nd-Fe-B
magnets, have been used in the electric and automobile industry and their usage increases
rapidly to meet the need to improve energy saving and to increase efficiency of electromagnetic
applications, for example traction motors for electric vehicles (EV) and hybrid electric vehicles
(HEV), which are urgently demanded to contribute to the problem of global warming.
However, there has been no standard method which can determine all the magnetic properties
of the high-performance permanent magnet materials with coercivity H higher than 2 MA/m to
cJ
meet the need of the industry. The method specified in IEC 60404-5, which is a method of
measurement in a closed magnetic circuit, can lead to significant measurement errors for
measurement of H ≥ 1,6 MA/m due to magnetic saturation in parts of the pole faces of the
cJ
yoke (see IEC 60404-5).
In order to solve the problem, several methods of measurement in an open magnetic circuit
without a yoke have been developed. The methods using a superconducting magnet (SCM) are
thought to solve this problem and enable accurate measurements of the high-performance
permanent magnet materials (see IEC TR 63304 [1] ).
Since the measurement in an open magnetic circuit is strongly affected by the self-
demagnetizing field in the test specimen, a correction of the influence of self-demagnetizing
field (demagnetizing field correction) on the demagnetization curve obtained in an open
magnetic circuit is indispensable.

___________
Numbers in square brackets refer to the Bibliography.

IEC 60404-18:2025 © IEC 2025 – 7 –
MAGNETIC MATERIALS –
Part 18: Permanent magnet (magnetically hard) materials –
Methods of measurement of the magnetic properties in
an open magnetic circuit using a superconducting magnet

1 Scope
The purpose of this part of IEC 60404 is to define the general principle and technical details of
the methods of measurement of the DC magnetic properties of permanent magnet materials in
an open magnetic circuit using a superconducting magnet (SCM).
This method is applicable to permanent magnet materials, such as those specified in
IEC 60404-8-1, the properties of which are presumed homogeneous throughout their volume.
There are two methods:
– the SCM-vibrating sample magnetometer (VSM) method;
– the SCM-extraction method.
This document also specifies methods to correct the influence of the self-demagnetizing field
in the test specimen on the demagnetization curve obtained in an open magnetic circuit. The
magnetic properties are determined from the corrected demagnetization curve.
NOTE 1 These SCM-methods can determine the magnetic properties of high-performance permanent magnet
materials with coercivity higher than 2 MA/m. For the magnetic materials with coercivity higher than 1,6 MA/m, the
methods of measurement in a closed magnetic circuit in accordance with IEC 60404-5 can lead to significant
measurement error due to magnetic saturation in parts of the pole faces of the yoke (see IEC 60404-5).
NOTE 2 There is another method of the measurement in an open magnetic circuit, i.e. the pulsed field
magnetometer (PFM), which is described in IEC TR 62331 [3]. The PFM is the method of measurement of the
magnetic properties of permanent magnet materials applying the pulsed magnetic field instead of the DC magnetic
field and is different from the methods described in this document. The PFM measures a steep AC magnetic response
of a test specimen in a pulsed magnetic field. Consequently, additional correction is indispensable to remove the
influence of eddy currents in the test specimen and the magnetic viscosity of the magnetic materials in order to obtain
properties equivalent to the DC magnetic properties.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050-121:1998, International Electrotechnical Vocabulary (IEV) – Part 121:
Electromagnetism
IEC 60050-151, International Electrotechnical Vocabulary (IEV) – Part 151: Electrical and
magnetic devices
IEC 60050-221:1990, International Electrotechnical Vocabulary (IEV) – Part 221: Magnetic
materials and components
IEC 60404-5, Magnetic materials – Part 5: Permanent magnet (magnetically hard) materials –
Methods of measurement of magnetic properties

– 8 – IEC 60404-18:2025 © IEC 2025
IEC 60404-8-1, Magnetic materials – Part 8-1: Specifications for individual materials –
Permanent magnet (magnetically hard) materials
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121,
IEC 60050-151, IEC 60050-221 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
demagnetization curve
part of a hysteresis loop in which the magnetic polarization goes from the remanent magnetic
polarization to zero when the applied magnetic field strength varies monotonically, as illustrated
in Figure 1
Key
J saturation magnetic polarization, in T
s
J remanent magnetic polarization, in T
r
H coercivity relating to the magnetic polarization, in A/m
cJ
Figure 1 – Demagnetization curve J(H)
Note 1 to entry: A demagnetization curve can be drawn from near magnetic saturation.
[SOURCE: IEC 60050-121:1998, 121-12-72, modified – "magnetic flux density" is replaced by
"magnetic polarization" and Note 1 to entry and Figure 1 have been added.]
3.1.2
magnetic dipole moment
m
vector quantity given by the volume integral of the magnetic polarization
[SOURCE: IEC 60050-221:1990, 221-01-07, modified – the symbol j is changed to m which is
used industrially and the note has been removed.]

IEC 60404-18:2025 © IEC 2025 – 9 –
3.1.3
M coil
detection coil for magnetic dipole moment
3.2 Abbreviated terms
ADC analogue-to-digital converter
EV electric vehicle
FEM finite element method
HEV hybrid electric vehicle
NMR nuclear magnetic resonance
PC personal computer
PFM pulsed field magnetometer
SCM superconducting magnet
SQUID superconducting quantum interference device
VSM vibrating sample magnetometer
4 General principle
4.1 Principle of the method
Figure 2 illustrates schematic diagrams of the test apparatus corresponding to a) the SCM-VSM
method and b) the SCM-extraction method. The test apparatus consists of a superconducting
magnet (SCM), a moving device, a specimen rod, a magnetic field sensor (hereafter H sensor),
a magnetic dipole moment detection coil (hereafter M coil), measuring devices and a data
processing device (PC).
The axis of the DC magnetic field generated by the SCM shall be vertical and coaxial with the
M coil and the specimen rod so that the direction of magnetization is parallel to the axis of the
specimen rod. The moving range of the test specimen shall be in a zone where the magnetic
field strength is uniform with a tolerance of ±1 % at the centre of the SCM. The H sensor shall
be placed in a position where the influence of the magnetic dipole moment of the test specimen
can be ignored.
The test specimen shall be firmly attached at the bottom end of the specimen rod to avoid
unexpected movement of the test specimen in the magnetic field and placed in the centre of
the SCM as shown in Figure 2.
– 10 – IEC 60404-18:2025 © IEC 2025

a) The SCM-VSM method b) The SCM-Extraction method
Figure 2 – Schematic diagrams of the test apparatus
The test specimen shall be initially magnetized to saturation (see 6.2) and be kept in the
remanent state. A DC magnetic field shall be applied to the test specimen in the direction
opposite to that used for the initial magnetization. The magnetic field strength is measured by
the H sensor (see 4.3).
The magnetic dipole moment of the test specimen is detected by the voltage induced in the M
coil due to the movement of the test specimen (see 4.4). The magnetic polarization of the test
specimen is calculated from the magnetic dipole moment and the volume of the test specimen
(see 7.2). For calibration aspects, see Clause 9.
There are two methods different in modes of the movement of the test specimen:
a) the SCM-VSM method: the test specimen is vibrated with a small amplitude in the M coil;
b) the SCM-extraction method: the test specimen is extracted through the M coil.
The measurements shall be carried out at an ambient temperature of (23 ± 5) °C unless
otherwise indicated.
NOTE The measurement at temperatures higher than the room temperature can be carried out using a heating unit
(see Annex C).
For permanent magnet materials which are known to have significant temperature coefficients
α(J ) and α(H ), the temperature of the test specimen shall be controlled within ±1 °C in the
r cJ
range between 19 °C and 27 °C during the measurements (see IEC 60404-5). The temperature
of the test specimen shall be measured by a non-magnetic temperature sensor attached directly
to the test specimen.
IEC 60404-18:2025 © IEC 2025 – 11 –
The demagnetization curve obtained in an open magnetic circuit is influenced strongly by the
self-demagnetizing field in the test specimen which opposes magnetization.
In order to determine the intrinsic demagnetization curve of the permanent magnet material, a
correction of the influence of the self-demagnetizing field (hereafter demagnetizing field
correction) shall be applied to the obtained demagnetization curve (see Clause 11). Magnetic
properties of the permanent magnet material shall be determined from the corrected
demagnetization curve.
4.2 Superconducting magnet (SCM)
A variable DC source supplies a DC current to the superconducting coil, with sufficiently low
voltage noise (see Figure 2). The current source shall be a bipolar type which can switch
positive-negative polarity continuously.
The SCM shall have enough capacity to generate a magnetic field strength to measure the
magnetic properties of high-performance permanent magnet materials with coercivity higher
than 2 MA/m, for example Nd-Fe-B sintered magnets. The capacity should be higher than
4,8 MA/m (6 T in magnetic flux density).
There are two types of SCM: the conventional metallic SCM made of metallic superconducting
coil and the ceramic SCM made of ceramic high temperature superconducting coil [1].
The ceramic SCM is recommended rather than the conventional metallic SCM, in order to
reduce the time required to obtain a demagnetization curve within several minutes and to
eliminate the use of expensive liquid helium and its incidental facilities, and this is particularly
convenient for industrial use [1].
NOTE The test apparatus using the ceramic SCM which can deal test specimens of industrial size is available
worldwide.
The zone of uniform magnetic field strength generated at the centre of the SCM shall be
sufficiently large to include the space of the moving test specimen.
4.3 Magnetic field strength sensor (H sensor)
An H sensor, for example a Hall probe, measures the magnetic field strength together with a
suitable H detection device (see Figure 2). The H sensor shall be calibrated by an appropriate
method such as nuclear magnetic resonance (NMR).
In the case of an SCM whose magnetic field strength is calibrated for the magnetizing current,
the magnetic field strength may be determined from the magnetizing current supplied to the
SCM. However, A small hysteresis shall be avoided between the magnetizing current and the
magnetic field strength of the SCM. In the case that it is not possible to avoid the small
hysteresis, the relationship between magnetizing current and magnetic field strength should be
precisely evaluated for increase and decrease of the magnetizing current.
The total measuring error of the magnetic field strength shall be smaller than ±1 %.
4.4 Magnetic dipole moment detection coil (M coil)
The M coil measures the magnetic dipole moment of the test specimen by the voltage induced
in it (see Figure 2). The M coil shall be wound coaxially with the axis of magnetic field and
placed symmetrically with respect to the centre of the magnetic field. Electrical leads of the M
coil shall be tightly twisted to avoid errors caused by voltages induced in loops of the leads.
The voltage induced in the M coil shall be calibrated using a standard specimen of nickel sphere
and the influence of the shape and dimensions of the test specimen on the voltage shall be
verified (see Clause 9).
– 12 – IEC 60404-18:2025 © IEC 2025
The total measuring error of the magnetic dipole moment shall be smaller than ±1 %.
The M coil used in this document is the first order gradiometer coil which shall be composed of
an upper coil and a lower coil connected electrically in opposite polarity as shown in Figure 3.
The second order gradiometer coil combined with a SQUID (superconducting quantum
interference device) circuit may also be used for the M coil [1].

a) The SCM-VSM method b) The SCM-Extraction method
Figure 3 – Schematic diagrams of the first order gradiometer coil
4.5 Specimen rod and moving device
The specimen rod shall be non-magnetic and shall have high rigidity to keep the test specimen
on the axis of the magnetic field without trembling.
The specimen rod shall be inserted vertically in the SCM and connected to the moving device
at the top end as shown in Figure 2.
The moving device may be a linear motor, a voice coil or other system which can move or
vibrate the specimen rod linearly along the axis of the magnetic field.
Moving modes of the test specimen are as follows.
a) The SCM-VSM method
The test specimen is vibrated along the axis of the magnetic field at a fixed frequency and
a fixed amplitude sufficiently smaller than the length of the M coil. The frequency is normally
20 Hz to 200 Hz and the amplitude is typically from 0,5 mm to 2 mm (see Figure 3 a)).
b) The SCM-extraction method
The test specimen is extracted through the M coil along the axis of the magnetic field. The
start point of the moving specimen is below the lower M coil or above the upper M coil (see
Figure 3 b)).
4.6 Measuring devices and data processing device
The voltage induced in the calibrated M coil due to the movement of the test specimen is
proportional to the magnetic dipole moment of the test specimen. The signal of the M coil is fed
to a preamplifier. In the case of the second order gradiometer coil, a SQUID circuit shall be
employed to integrate the signal (see Figure 2).
In the SCM-VSM method, the amplified signal is fed to a phase sensing device such as a lock-
in amplifier to output the amplitude of the signal synchronized to the vibration frequency of the
test specimen. The output signal is fed to the data processing device.
NOTE In the SCM-VSM method, there is no drift in the signal of the magnetic dipole moment, owing to the use of a
phase sensing device (lock-in amplifier) in the SCM-VSM.

IEC 60404-18:2025 © IEC 2025 – 13 –
In the SCM-extraction method, the amplified signal is directly fed to the data processing device.
The output signal of the H detection device, which is proportional to the magnetic field strength,
is fed to the data processing device.
The data processing device is usually composed of a digitizer and a digital signal calculator for
the determination of the magnetic properties. The digitizer converts the input signals into digital
data simultaneously with analogue-to-digital converters (ADC). The ADC shall have at least a
16-bit resolution.
The digital signal calculator is usually a personal computer (PC) and calculates the magnetic
properties from the digitized signals of the magnetic dipole moment and the magnetic field
strength.
5 Test specimen
The shape of the test specimen shall be a cylinder or cuboid.
The ratio of the length L to the dimension D, i.e. L/D, shall be 1,00 within ±0,05, where D is the
edge length of the cuboid test specimen or the diameter of the cylinder test specimen. In the
case of a cuboid with L/D = 1,00, the direction of magnetization shall be marked properly during
the test specimen preparation. The direction of magnetization shall be parallel to the length L
of the specimen.
NOTE 1 A small difference between L and D of a cuboid test specimen is convenient to easily identify the
magnetizing direction of the test specimen.
The dimensions of the test specimen, i.e. L and D, shall be equal to or larger than 3 mm but
sufficiently smaller than that of the M coil [1].
The test specimen shall be cut carefully to the predetermined dimension from a large block of
the permanent magnet material. Damage on its surface shall be avoided as much as possible,
which can deteriorate the magnetic properties.
Test specimens with a dimension less than 3 mm may be used, provided that the damaged
surface layer is negligible or a special treatment is applied on the damaged surface layer to
recover the intrinsic magnetic properties.
The test specimen should be marked with an arrow to indicate the direction of magnetization in
order to make it easy to attach the test specimen to the specimen rod.
NOTE 2 The thickness of permanent magnet materials used in industry has become thinner as their magnetic
properties have improved, and permanent magnets thinner than 5 mm have come to be widely used in industry. It is
not impossible to measure the magnetic properties of permanent magnet materials with test specimens obtained from
these magnets by the conventional test method described in IEC 60404-5 that defines the dimensions of the test
specimens to be 5 mm or more. Therefore, a new test method to measure magnetic properties of permanent magnet
materials for smaller test specimen has been required by industry. Fundamentally, for test specimens smaller than
5 mm cube, the measurement reproducibility of the conventional closed magnetic circuit measurement becomes
worse by influence of the air-gap between the test specimen and the pole pieces. The air-gap caused by poor
machining accuracy generates local demagnetizing field in the test specimen and tends to create a risk of cracking.
Due to these backgrounds, the open magnetic circuit measurement is required in industry.

– 14 – IEC 60404-18:2025 © IEC 2025
6 Preparation of measurement
6.1 Measurement of volume of the test specimen
The volume V of the test specimen shall be calculated from the mass and the density of the test
specimen. The mass of the test specimen shall be determined accurately by means of a
calibrated electronic balance. The density of the test specimen shall be determined accurately
with a large block of the permanent magnet material, for example water displacement
measurement based on Archimedean principle.
The volume V can also be calculated from the dimensions of the test specimen measured by
means of a calibrated micrometer with four significant figures.
The volume V of the test specimen shall be determined within a tolerance of ±1 %.
6.2 Initial magnetization of the test specimen to saturation
Before measurement, the test specimen shall be magnetized to saturation in a DC magnetic
field strength H .
mag
If it is not possible to magnetize the test specimen to saturation in the test apparatus, the test
specimen shall be magnetized to saturation outside the test apparatus in a superconducting
coil or a pulse magnetizer in accordance with IEC 60404-5.
Recommended values for the DC magnetic field strength H for various permanent magnet
mag
materials can be found in IEC TR 62517 [4].
7 Determination of magnetic polarization
7.1 Measurement of the magnetic dipole moment
7.1.1 SCM-VSM method
In the SCM-VSM method, the test specimen shall be vibrated at a fixed frequency and a fixed
amplitude, and then the output voltage of the phase sensing device shall be measured (see
4.6).
The magnetic dipole moment m shall be calculated from Formula (1):
C U
VV
m = (1)
af⋅
where
m is the magnetic dipole moment, in Wb·m;
U is the output voltage of the phase sensing device, in V;
V
C is a constant, in m ;
V
a is the amplitude of the vibration, in m;
f is the frequency of the vibration, in Hz.
The constant C shall be determined by a calibration of the M coil (see Clause 9).
V
IEC 60404-18:2025 © IEC 2025 – 15 –
7.1.2 SCM-extraction method
In the SCM-extraction method, the test specimen shall be extracted through the M coil. The
output voltage of the preamplifier or the SQUID circuit shall be measured (see 4.6).
The magnetic dipole moment shall be calculated from Formula (2):
t
m= CdUt() t
(2)
∫
t
where
m is the magnetic dipole moment, in Wb·m;
U(t) is the output voltage of the preamplifier or the SQUID circuit, in V;
t is the time when the test specimen goes through the lower part of the M coil and U(t ) = 0,
1 1
in s;
t is the time when the test specimen goes through the upper part of the M coil and U(t ) = 0,
2 2
in s;
C is a constant, in m.
The constant C shall be determined by a calibration of the M coil (see Clause 9).
7.2 Determination of magnetic polarization
The magnetic polarization J shall be calculated from the magnetic dipole moment m and the
volume of the test specimen V according to Formula (3).
m
J= (3)
V
where
J is the magnetic polarization, in T;
m is the magnetic dipole moment, in Wb∙m;
V is the volume of the test specimen, in m .
8 Measurement of magnetic field
The magnetic field strength H corresponding to the magnetic polarization shall be measured by
the calibrated H sensor, for example a Hall probe, and the H detection device (see Figure 2).
The temperature dependence of the measuring instrument shall be taken into account.

– 16 – IEC 60404-18:2025 © IEC 2025
9 Calibration of the magnetic dipole moment detection coil (M coil)
The calibration of the M coil shall be carried out by measuring a standard specimen of nickel
sphere for which the magnetic dipole moment m at an ambient temperature of (23 ± 5) °C and
an applied magnetic fiel
...