IEC TR 62797:2013

IEC/TR 62797 ®
Edition 1.0 2013-08
TECHNICAL
REPORT
colour
inside
International comparison of measurements of the magnetic moment using
vibrating sample magnetometers (VSM) and superconducting quantum
interference device (SQUID) magnetometers

IEC/TR 62797:2013(E)
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IEC/TR 62797 ®
Edition 1.0 2013-08
TECHNICAL
REPORT
colour
inside
International comparison of measurements of the magnetic moment using

vibrating sample magnetometers (VSM) and superconducting quantum

interference device (SQUID) magnetometers

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
V
ICS 29.030 ISBN 978-2-8322-1018-5

– 2 – TR 62797  IEC:2013(E)
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Overview . 7
3 Samples . 8
3.1 Hard ferrites . 8
3.2 Magnetic tapes . 8
4 Measuring quantities and measuring conditions . 8
4.1 General . 8
4.2 Hard ferrite spheres . 8
4.3 Magnetic tape samples . 9
4.4 Role of the measuring temperature . 9
5 Analysis of the measured quantities . 10
Annex A (informative) International comparison of measurements of the magnetic
moment using vibrating sample magnetometers and SQUID magnetometers . 15
Annex B (informative) Participants . 30
Bibliography . 31

Figure 1 – Isotropic and anisotropic ferrites: standard deviations . 12
Figure 2 – Magnetic tape samples: standard deviations . 12
Figure 3 – Isotropic and anisotropic ferrites: weighted uncertainties . 13
Figure 4 – Magnetic tape samples: weighted uncertainties . 13
Figure 5 – Normalized best values y /< y> of the coercive field strength H and
i cJ
maximum energy product (BH) . 14
max
Figure A.1 – Dispersion of the J values measured by the participating laboratories
800k
on the isotropic ferrite sample HF-Iso1 . 16
Figure A.2 – Dispersion of the J values measured by the participating laboratories on
r
the isotropic ferrite sample HF-Iso1 . 17
Figure A.3 – Dispersion of the H values measured by the participating laboratories
cJ
on the isotropic ferrite sample HF-Iso1 . 18
Figure A.4 – Dispersion of the H values measured by the participating laboratories
cB
on the isotropic ferrite sample HF-Iso1 . 19
Figure A.5 – Dispersion of the (BH) values measured by the participating
max
laboratories on the isotropic ferrite sample HF-Iso1 . 20
Figure A.6 – Dispersion of the J values measured by the participating laboratories
800k
on the anisotropic ferrite sample HF-Aniso1 . 21
Figure A.7 – Dispersion of the J values measured by the participating laboratories on
r
the anisotropic ferrite sample HF-Aniso1. 22
Figure A.8 – Dispersion of the H values measured by the participating laboratories
cJ
on the anisotropic ferrite sample HF-Aniso1 . 23
Figure A.9 – Dispersion of the H values measured by the participating laboratories
cB
on the anisotropic ferrite sample HF-Aniso1 . 24
Figure A.10 – Dispersion of the (BH) values measured by the participating
max
laboratories on the anisotropic ferrite sample HF-Aniso1 . 25
Figure A.11 – Dispersion of the m values measured by the participating
400k
laboratories on the magnetic tape sample A1 . 26

TR 62797  IEC:2013(E) – 3 –
Figure A.12 – Dispersion of the m values measured by the participating laboratories
r
on the magnetic tape sample A1 . 27
Figure A.13 – Dispersion of the S = m /m values measured by the participating
r 400k
laboratories on the magnetic tape sample A1 . 28
Figure A.14 – Dispersion of the H values measured by the participating laboratories
cJ
on the magnetic tape sample A1 . 29

Table A.1 – Magnetic polarization value J at H = H = 800 kA/m measured by
800k a peak
the participating laboratories on the isotropic hard ferrite HF-Iso1 . 15
Table A.2 – Remanent magnetic polarization J measured by the participating
r
laboratories on the isotropic hard ferrite HF-Iso1 . 17
Table A.3 – Coercive field H measured by the participating laboratories on the
cJ
isotropic hard ferrite HF-Iso1 . 18
Table A.4 – Coercive field H measured by the participating laboratories on the
cB
isotropic hard ferrite HF-Iso1 . 19
Table A.5 – Maximum energy product (BH) measured by the participating
max
laboratories on the isotropic hard ferrite HF- Iso1 . 20
Table A.6 – Magnetic polarization value J at H = H = 800 kA/m measured by
800k a peak
the participating laboratories on the anisotropic hard ferrite HF-Aniso1 . 21
Table A.7 – Remanent magnetic polarization J measured by the participating
r
laboratories on the anisotropic hard ferrite HF-Aniso1. 22
Table A.8 – Coercive field H measured by the participating laboratories on the
cJ
anisotropic hard ferrite HF-Aniso1 . 23
Table A.9 – Coercive field H measured by the participating laboratories on the
cB
anisotropic hard ferrite HF-Aniso1 . 24
Table A.10 – Maximum energy product (BH) measured by the participating
max
laboratories on the anisotropic hard ferrite HF- Aniso1. 25
Table A.11 – Magnetic moment m measured at at H = H = 400 kA/m by the
400k a peak
participating laboratories on the magnetic tape sample 1A . 26
Table A.12 – Remanent magnetic moment m measured by the participating
r
laboratories on the magnetic tape sample 1A . 27
Table A.13 – Squareness ratio S = m /m measured by the participating
r 400k
laboratories on the magnetic tape sample 1A . 28
Table A.14 – Coercive field H measured by the participating laboratories on the
cJ
magnetic tape sample 1A . 29

– 4 – TR 62797  IEC:2013(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INTERNATIONAL COMPARISON OF MEASUREMENTS OF
THE MAGNETIC MOMENT USING VIBRATING SAMPLE
MAGNETOMETERS (VSM) AND SUPERCONDUCTING
QUANTUM INTERFERENCE DEVICE (SQUID) MAGNETOMETERS

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 62797, which is a technical report, has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
68/448/DTR 68/454/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.

TR 62797  IEC:2013(E) – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – TR 62797  IEC:2013(E)
INTRODUCTION
Following a proposal made at the meeting of IEC TC 68 Working Group 2 (Magnetic alloys
and steels – Measuring methods) in Braunschweig (PTB, 13-14 November 2006), an
intercomparison exercise was started regarding the measurement of the magnetic moment by
means of the vibrating sample magnetometer (VSM) method. The VSM finds widespread use
in industrial and research laboratories, because of its sensitivity, ruggedness, and relative
simplicity of use [1] . It is not an absolute method and requires calibration by means of a
reference sample. This is typically represented by a very pure Ni sphere, calibrated by means
of an independent method [2]. The VSM is generally applied for the characterization of hard
magnetic materials, but, depending on the specific sensitivity of the apparatus, can also be
used to test paramagnetic and diamagnetic materials. Its application to magnetically soft
materials is generally restricted to the determination of the saturation magnetization. In fact,
being an open circuit method, the VSM is not suited to the measurement of the magnetization
curve of soft magnetic materials.
The basic aim of this comparison is to verify the degree of reproducibility of the method, a
prerequisite for the prospective development of a related IEC measuring standard. The
existing ASTM Standard A894/894M-00 [3] is devoted to the determination of the saturation
magnetization of nonmetallic magnetic materials. Ten different research laboratories, listed in
Annex B, agreed to participate in the comparison exercise. Each laboratory was assumed to
have appropriate traceability of measurements and was required to determine the
measurement uncertainty according to the ISO/IEC Guide to the expression of uncertainty in
measurement [4]. Two laboratories used superconducting quantum interference device
(SQUID) magnetometers.
The comparison was coordinated by INRIM (Istituto Nazionale di Ricerca Metrologica, Torino,
Italy) and the Hannam University (Taejon, Korea). A summarizing paper on these experiments
was presented at the International Workshop on One- and Two-Dimensional Measurement
and Testing (Vienna, September 2012) and is to be published on the Int. J. Appl.
Electromagnetics and Mechanics [8].

Numbers in square brackets refer to the Bibliography.

TR 62797  IEC:2013(E) – 7 –
INTERNATIONAL COMPARISON OF MEASUREMENTS OF
THE MAGNETIC MOMENT USING VIBRATING SAMPLE
MAGNETOMETERS (VSM) AND SUPERCONDUCTING
QUANTUM INTERFERENCE DEVICE (SQUID) MAGNETOMETERS

1 Scope
This Technical Report provides the results of an international comparison of measurements of
the magnetic moment, using vibrating sample magnetometers (VSM) and superconducting
quantum interference device (SQUID) magnetometers.
The basic object of this comparison is to verify the degree of reproducibility of the method
employed as a prerequisite for the prospective development of a related IEC measuring
standard.
2 Overview
In this report an intercomparison exercise on the measurement of the magnetic moment by
means of the vibrating sample magnetometer (VSM) and superconducting quantum
interference device (SQUID) magnetometer is presented. The VSM finds widespread use in
industrial and research laboratories, because of its sensitivity, ruggedness, and relative
simplicity of use. The basic aim of this comparison was to verify the degree of reproducibility
of the VSM method, as a prerequisite for the prospective development of a related IEC
measuring standard. At present time, the VSM method is invoked in the ASTM Standard
A984, which is devoted, however, exclusively to the determination of the saturation
magnetization of nonmetallic magnetic materials. An exercise was carried out by ten different
laboratories regarding the measurement of the hysteresis loop parameters in hard ferrites and
the magnetic moment in tape samples by means of the VSM (SI units). Each laboratory was
assumed to have appropriate traceability of measurements and was required to determine the
measurement uncertainty according to the ISO/IEC Guide to the expression of uncertainty in
measurement. The comparison was coordinated by INRIM. The results were analyzed
according to standard rules (e.g. ISO and EURAMET guidelines).
The following relative standard deviations of the laboratories best estimates around the
unweighted mean were found:
a) Anisotropic hard ferrites: coercive field H ∼ 1,0 %; coercive field H ∼ 0,9 %;
cJ cB
polarization at applied field H ∼ 800 kA/m J ∼ 0,80 %; remanent polarization J ∼
a 800k r
1,8 %; maximum energy product (BH) ∼ 1,2 %.
max
b) Isotropic hard ferrites: coercive field H ∼ 1,0 %; coercive field H ∼ 3,5 %; polarization
cJ cB
at applied field H = 800 kA/m J ∼ 1,2 %; remanent polarization J ∼ 3,2 %; maximum
a 800k r
energy product (BH) ∼ 6,2 %.
max
c) Magnetic tape samples: magnetic moment at H = 400 kA/m m ~ 1,8 % - 2,8 %;
a 400k
remanent magnetic moment m ~ 1,3 % - 1,6 %; squareness S ~ 2,0 %; coercive field
r
H ~ 1,1 % - 2,2 %.
cJ
– 8 – TR 62797  IEC:2013(E)
3 Samples
3.1 Hard ferrites
Two different types of hard ferrite spherical samples (isotropic and anisotropic) were prepared
at INRIM by grinding commercial sintered ferrite specimens. Two samples for each type were
circulated.
• Isotropic hard ferrite spherical sample. Label: HF_iso1. Mass m = 74,50 mg.
3 3
Density δ = 4 950 kg/m . Volume V = 15,05 mm .
• Isotropic hard ferrite spherical sample. Label: HF_iso2. Mass m = 77,15 mg.
3 3
Density δ = 4 950 kg/m . Volume V = 15,59 mm .
• Anisotropic hard ferrite spherical sample. Label: HF_anis1. Mass m = 73,33 mg.
3 3
Density δ = 4 870 kg/m . Volume V = 15,06 mm .
• Anisotropic hard ferrite spherical sample. Label: HF_anis2. Mass m = 73,31 mg.
3 3
Density δ = 4 870 kg/m . Volume V = 15,06 mm .
The circulation of the samples started with measurements made at INRIM. After completion of
the measurements by all the other laboratories, INRIM measured the sample mass again and
repeated the magnetic measurements. A slight decrease of the mass, which ranged from
0,2 % to 0,3% in all samples, was eventually found. No attempt was made, however, to
correct for this loss of mass, which presumably took place gradually along the exercise. Its
effect has been assumed to be incorporated in the overall measuring uncertainty.
3.2 Magnetic tapes
Disk samples were cut from two different types of magnetic tape at Hannam University and
dispatched to INRIM before starting the circulation. Two samples for each type were tested.
• Tape 1A. Mass m = 1,258 mg. Diameter d = 3 mm.
• Tape 1B. Mass m = 1,248 mg. Diameter d = 3 mm.
• Tape 2A. Mass m = 1,246 mg. Diameter d = 3 mm.
• Tape 2B. Mass m = 1,205 mg. Diameter d = 3 mm.
Again, INRIM tested the samples at the beginning and at the end of the exercise. It was found
that Tape 1B and Tape 2B samples were damaged. The measurements concerning Tape 1A
and Tape 2A only were therefore retained for analysis.
4 Measuring quantities and measuring conditions
4.1 General
A demagnetization procedure before starting the measurements was recommended. The
suggested maximum peak value of the magnetic field strength to be progressively and
cyclically decreased, was H ≥ 800 kA/m.
a,peak,max
4.2 Hard ferrite spheres
Before starting the measurement, the demagnetized spherical samples were oriented with
their macroscopic easy axis aligned with the applied field direction. A simple way to achieve
alignment is to let the sample free to orient itself in a weak field. Fine adjustments may
possibly be done on site by looking for maximum VSM response. Notice that the nominally
isotropic sample is endowed with slight macroscopic anisotropy. Previous experiments
showed that a ± 5° misalignment in anisotropic samples can lead to a decrease of the
measured remanence around 1 %. A similar decrease occurs in the typical isotropic ferrites
for a misalignment as high as 30° - 40°. The measurement in this material is therefore
negligibly affected by imperfect orientation of the easy axis along the applied field direction.

TR 62797  IEC:2013(E) – 9 –
The applied field was then increased up to H = 800 kA/m and the return magnetization
a,peak
curve was recorded, after correction for the demagnetizing effect. The effective field was
N
d
H=H − J
a
obtained as , with H the applied field, J the magnetic polarization, µ =
a 0
µ
-7
4π⋅10 Vs/Am, and the demagnetizing coefficient, under the assumption of a perfectly
spherical sample, N = 1/3. The following quantities were measured:
d
• Magnetic polarization J at H = H = 800 kA/m;
800k a a,peak
• Remanent polarization J for H = 0;
r
• Coercive fields H and H ;
cB cJ
• Maximum energy product (BH) .
max
4.3 Magnetic tape samples
Before starting the measurement, the demagnetized disk-shaped samples were oriented with
their macroscopic easy axis aligned with the applied field direction. A faint mark on the disk
surface indicated the easy axis. The applied field was increased up to H = 400 kA/m and
a,peak
subsequently decreased down to the symmetric value -H = -400 kA/m. No correction for
a,peak
the demagnetizing field was made.
The following quantities were determined:
• Magnetic moment m for H = H = 400 kA/m;
400k a a,peak
• Remanent moment m for H = 0;
r a
• Squareness S = m / m ;
r 400k
• Coercive field H .
cJ
While the intercomparison was specifically directed at evaluating the reproducibility of the
VSM method, two of the laboratories (PTB and NPL) performed their measurements by means
of a SQUID magnetometer. SI units were used all along the experiments.
4.4 Role of the measuring temperature
The prescribed measuring temperature was 23 °C ± 1 °C. This temperature refers to the
region occupied by the sample and the sensing coils, which, due to possible heating of the
electromagnet, may be slightly different from the room temperature.
INRIM performed specific measurements by changing the sample temperature between 19 °C
and 26 °C, in order to determine the temperature coefficient of the measured quantities.
Laboratories making the measurements at temperatures different from 23 °C could correct
their results according to value and sign of these coefficients.
1) Isotropic and anisotropic hard-ferrites (HF_iso1, HF_iso2, HF_anis1, HF_anis2).
dH
o
cJ
a) Coercive field H α = ⋅ =+0,2 % C
hcJ
cJ
H dT
cJ
1 dH
cB −2 o
b) Coercive field H
α = ⋅ =+5⋅10 % C
cB
hcB
H dT
cB
c) Remanence and peak polarization values J 1 dJ
o
α = ⋅ =−0,12 % C
J
J dT
2) Magnetic tapes (1A, 1B, 2A, 2B)
dH
c −2 o
a) Coercive field H
α = ⋅ =−8⋅10 % C
c
hc
H dT
c
– 10 – TR 62797  IEC:2013(E)
1 dm
b) Magnetic moment m o
α = ⋅ =−0,2 % C
m
m dT
5 Analysis of the measured quantities
The figures provided by the participating laboratories were collected and analyzed according
to standard rules [4]. For each measured quantity y and each sample, two types of reference
i
N
values were determined. The first is the unweighted mean value <
...