IEC 60404-7:2019

Magnetic materials - Part 7: Method of measurement of the coercivity (up to 160 kA/m) of magnetic materials in an open magnetic circuit

IEC 60404-7:2019 specifies a method of measurement of the coercivity of magnetic materials in an open magnetic circuit. This document is applicable to all magnetic materials with coercivities from 0,2 A/m to 160 kA/m.
This edition includes the following significant technical changes with respect to the previous edition:
Clause 1: The scope includes a more detailed description of the magnetic materials which applies to this standard;
Clause 4: Figure 2 – circuit diagram for methods A and B was simplified and the fluxgate probes inside the solenoid have been added;
Clause 7: Compensation for the earth’s magnetic field and for static and dynamic magnetic noise fields has been added;
Clause 8: Magnetic shielding of the measuring region has been added;
9.2.2: The measuring methods for local and integral measurement of the flux in the test specimen have been separated and the limitations in size and shape of the test specimen have been considered.
9:3: The method C with a VSM (Vibrating Sample Magnetometer) has been moved from 9.3 to the Annex B.
The term "complex shaped test specimen" has been replaced in several clauses by "test specimen different from ellipsoids".
The character of Annex A has been changed from “informative” to “normative”.

Matériaux magnétiques - Partie 7: Méthode de mesure de la coercitivité (jusqu'à 160 kA/m) des matériaux magnétiques en circuit magnétique ouvert

L'IEC 60404-7:2019 spécifie une méthode de mesure de la coercitivité des matériaux magnétiques en circuit magnétique ouvert. Le présent document est applicable à l'ensemble des matériaux magnétiques dont les valeurs de coercitivité sont comprises entre 0,2 A/m et 160 kA/m.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
Article 1: le domaine d'application inclut une description plus complète des matériaux magnétiques qui s'applique à la présente norme;
Article 4 – Figure 2: le schéma du circuit pour les Méthodes A et B a été simplifié et les sondes de flux à seuil à l'intérieur du solénoïde ont été ajoutées;
Article 7: la compensation du champ magnétique terrestre et des champs magnétiques parasites statiques et dynamiques a été ajoutée;
Article 8: le blindage magnétique de la zone de mesure a été ajouté;
9.2.2: les méthodes de mesure pour le mesurage local et intégral du flux dans l'éprouvette ont été séparées, et les limites de taille et de forme de l'éprouvette ont été prises en compte;
9.3: la Méthode C avec un VSM (magnétomètre à échantillon vibrant) a été déplacée du 9.3 à l'Annexe B;
le terme "éprouvette de forme complexe" a été remplacé dans plusieurs articles par le terme "éprouvette différente des ellipsoïdes";
le statut de l'Annexe A a été modifié; cette annexe n'est plus '"informative" mais "normative".

General Information

• Status: Published
• Publication Date: 15-Jan-2019
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• ICS: 29.030 - Magnetic materials
• Technical Committee: TC 68 - Magnetic alloys and steels
• Drafting Committee: WG 2 - TC 68/WG 2
• Current Stage: PPUB - Publication issued
• Start Date: 16-Jan-2019
• Completion Date: 14-Jan-2019

Standards Content (Sample)

IEC 60404-7 ®
Edition 2.0 2019-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 7: Method of measurement of the coercivity (up to 160 kA/m) of magnetic
materials in an open magnetic circuit

Matériaux magnétiques –
Partie 7: Méthode de mesure de la coercitivité (jusqu'à 160 kA/m) des matériaux
magnétiques en circuit magnétique ouvert

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IEC 60404-7 ®
Edition 2.0 2019-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 7: Method of measurement of the coercivity (up to 160 kA/m) of magnetic

materials in an open magnetic circuit

Matériaux magnétiques –
Partie 7: Méthode de mesure de la coercitivité (jusqu'à 160 kA/m) des matériaux

magnétiques en circuit magnétique ouvert

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.030; 17.220.20 ISBN 978-2-8322-6385-3

– 2 – IEC 60404-7:2019 © IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle of the method . 7
5 Test specimen . 8
6 Solenoid . 8
7 Compensation for the earth’s magnetic field and static and dynamic magnetic
noise fields . 8
8 Magnetic shielding of the measurement region . 8
9 Measurement . 8
9.1 Magnetization . 8
9.2 Measuring methods . 9
9.2.1 General . 9
9.2.2 Method A . 9
9.2.3 Method B . 10
9.3 Determination of coercivity . 11
9.4 Reproducibility . 12
10 Test report . 13
Annex A (normative)  Precautions to be taken for measurements of coercivity below
40 A/m, with a complex shaped test specimen and some special cases . 14
A.1 Coercivity below 40 A/m . 14
A.2 Coercivity measurement of test specimens with complex shapes . 14
A.3 Optimization of the amplitude and time of the magnetizing cycle for a test
specimen of soft magnetic material . 14
A.4 Mechanical stress and heating of the test specimen in the solenoid . 14
Annex B (informative) Method C with a VSM (Vibrating Sample Magnetometer) . 15
Bibliography . 17

Figure 1 – Demagnetizing B(H) and J(H) curves from saturation . 6
Figure 2 – Circuit diagram for Methods A and B . 7
Figure 3 – Method A, magnetic flux sensing probe: Hall probe . 9
Figure 4 – Method A, magnetic flux sensing probe: differential fluxgate probe . 10
Figure 5 – Method B, magnetic flux sensing probe: differential fluxgate probe . 11
Figure 6 – Magnetic polarisation J over the length L of a cylindrical rod . 12
Figure B.1 – Schematic diagram of Method C with a VSM . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 7: Method of measurement of the coercivity (up to 160 kA/m) of
magnetic materials in an open magnetic circuit

FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60404-9 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This second edition cancels and replaces the first published in 1982. This edition constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Clause 1: The scope includes a more detailed description of the magnetic materials which
applies to this standard;
b) Clause 4: Figure 2 – circuit diagram for methods A and B was simplified and the fluxgate
probes inside the solenoid have been added;
c) Clause 7: Compensation for the earth’s magnetic field and for static and dynamic
magnetic noise fields has been added;

– 4 – IEC 60404-7:2019 © IEC 2019
d) Clause 8: Magnetic shielding of the measuring region has been added;
e) 9.2.2: The measuring methods for local and integral measurement of the flux in the test
specimen have been separated and the limitations in size and shape of the test specimen
have been considered.
f) 9:3: The method C with a VSM (Vibrating Sample Magnetometer) has been moved from
9.3 to the Annex B.
g) The term "complex shaped test specimen" has been replaced in several clauses by "test
specimen different from ellipsoids".
h) The character of Annex A has been changed from “informative” to “normative”.
The text of this International Standard is based on the following documents:
CDV Report on voting
68/596/CDV 68/608A/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
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 "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
MAGNETIC MATERIALS –
Part 7: Method of measurement of the coercivity (up to 160 kA/m) of
magnetic materials in an open magnetic circuit

1 Scope
This part of IEC 60404 specifies a method of measurement of the coercivity of magnetic
materials in an open magnetic circuit.
This document is applicable to all magnetic materials with coercivities from 0,2 A/m to
160 kA/m.
NOTE Examples of magnetic materials covered by this document are amorphous alloys, nanocrystalline alloys, all
softmagnetic crystalline materials (e.g. Fe, FeSi-, CoFe- and FeNi-alloys), soft ferrites, hard metals, semi-hard
magnetic alloys (e.g. FeCoTiAl-, FeCoV-, FeCrCo- and AlNiCo-alloys) [1] .
Special precautions are to be taken in measuring coercivities below 40 A/m, in materials with
high conductivity and in test specimens which have a shape different from ellipsoids (see
Annex A).
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.
There are no normative references in this document.
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
coercivity H
cJ
value of the coercive field strength in a material when the magnetic flux density, magnetic
polarization or magnetization is brought from saturation by a monotonically changing magnetic
field to zero
Note 1 to entry: The parameter that is varied should be stated, and the appropriate symbol used as follows: H
cB
for the coercivity relating to the magnetic flux density, H for the coercivity relating to the magnetic polarization,
cJ
H for the coercivity relating to the magnetization. The first two symbols supersede H and H respectively.
cM cB cJ
—————————
Numbers in square brackets refer to the Bibliography.

– 6 – IEC 60404-7:2019 © IEC 2019
3.2
demagnetize
to reduce the magnetic flux density of a magnetized material along the demagnetization curve
Note 1 to entry: The coercivities H and H are respectively discriminated depending on the hysteresis loop
cB cJ
being defined in the B = f(H) or J = f(H) system (see Figure 1). It can be shown that, for materials of
high-differential permeability in the region B = 0, the difference between the coercivity H and the coercivity H is
cJ cB
negligible since:
∆H
 
1 µ
H = H  − 
cB cJ 0
∆B
 
(1)
where
H coercivity relating to the magnetic flux density, in amperes per metre;
cB
H coercivity relating to the magnetic polarization, in amperes per metre;
cJ
ΔB incremental change in magnetic flux density (at B = 0), in teslas;
ΔH corresponding change in magnetic field strength, in amperes per metre;
-7
µ magnetic constant (4π x 10 in henrys per metre).
o
Key
B magnetic flux density, in teslas
J magnetic polarization, in teslas
H magnetic field strength, in amperes per metre
B remanent flux density in, teslas
r
B flux density in air in, teslas
J remanent magnetic polarization, in teslas
r
J saturation magnetic polarization, in teslas
s
Figure 1 – Demagnetizing B(H) and J(H) curves from saturation

4 Principle of the method
If a magnetic test specimen is placed in a uniform and unidirectional magnetic field then it will
distort this magnetic field unless a condition that no flux (additional to that previously carried
by the air space it now occupies) enters or emerges from the test specimen. This condition
represents a state of complete demagnetization which occurs when a demagnetizing coercive
magnetic field strength is applied to the test specimen such that the magnetic polarization is
zero [2].
The test specimen is magnetized to saturation (J ) and then the magnetic field is reduced
s
smoothly without interruption to zero (J ). Afterwards the polarity of the magnetic field is
r
reversed and a demagnetizing field is increased until the magnetic polarization of the test
specimen is zero. The applied magnetic field strength required to achieve this condition is
measured and defined as the coercivity H of the test specimen (see Figure 1).
cJ
A magnetic flux sensing probe enables the detection of the condition of no distortion of a
uniform magnetic field by the test specimen and provides the means for determining the
coercivity.
For this measurement, the test specimen and the magnetic flux sensing probes are placed in
an open magnetic circuit in the uniform and unidirectional magnetic field of a solenoid. The
flux sensing probe should be placed as follows:
a) inside the solenoid, close to the end of the test specimen (Method A – Hall probe,
see Figure 3), or
b) inside the solenoid, at a distance from the test specimen, depending on the size and
permeability of the test specimen (Method A – differential fluxgate probe, see Figure 4), or
c) outside the solenoid (Method B – differential fluxgate probe, see Figure 5).
The solenoid and measuring equipment shall be connected as shown in Figure 2.
NOTE There is an alternative way to use an axially vibrating search coil as magnetic sensing probe like
Method A [3].
Figure 2 – Circuit diagram for Methods A and B
Alternatively, the test specimen is placed at the centre of the gap of an electromagnet as in
Method C, see Annex B.
– 8 – IEC 60404-7:2019 © IEC 2019
5 Test specimen
The shape and the dimensions of the test specimen may be varied provided that they meet
the following conditions:
a) the test specimen can be placed inside the solenoid so that its major axis is coincident
with the axis of the solenoid;
b) the test specimen can be magnetized to saturation.
NOTE For the effects of shape and non-uniform magnetic properties of the test specimen refer to 9.2.2 and 9.3.
6 Solenoid
The magnetic field in the solenoid shall have the following specifications:
a) the magnetic field strength in the solenoid over the volume of the test specimen shall not
vary by more than ±0,5 %;
b) an AC ripple of the magnetic field strength in the solenoid shall be less than ±0,5 % of the
magnetic field strength.
7 Compensation for the earth’s magnetic field and static and dynamic
magnetic noise fields
The measurement of the coercivity of a test specimen of soft magnetic material can be
distorted by the earth’s magnetic field and by external static and dynamic magnetic noise
fields. Compensation for these can be achieved either by:
a) a suitable compensation system for the earth’s magnetic field [4] or a magnetic shield
placed around the measurement region, or
b) the magnetic flux sensing probe for the measurement of the stray magnetic field of the test
specimen is a differential fluxgate probe to suppress an influence of these uniform
external magnetic fields (see Figures 4 and 5).
8 Magnetic shielding of the measurement region
The magnetic shielding shall be constructed from a high magnetic permeability material [1].
Any influence from the magnetic shielding on the magnetic field in the measurement region
has to be compensated for.
After magnetizing the test specimen to saturation, the magnetic shielding must be completely
demagnetized from the point of the magnetic remanence, to avoid light magnetizing of the test
specimen by the residual field of the magnetic shielding. This residual magnetic field from the
magnetic shielding inside the solenoid has to be smaller than 5 % of the measured stray
magnetic field of the test specimen in the magnetic remanence. The demagnetizing field of
the magnetic shielding shall not affect the test specimen, magnetically.
9 Measurement
9.1 Magnetization
The test specimen is magnetized to saturation in:
a) the solenoid of the coercivity measuring device as in Method A and Method B, or
b) a separate device which can be, for example, a system with a permanent magnet or an
electromagnet, or a pulsed magnetizing coil.

Saturation is considered to be achieved when an increase of 50 % in the magnetizing field
strength gives an increase in the coercivity of less than 1 %.
The saturation field shall be held long enough, usually 0,5 s, to ensure complete penetration
of the material.
Magnetic materials having a low coercivity and a high electrical conductivity require a
reduction of the magnetizing field from saturation to zero to be conducted very smoothly
without interruptions. This is to avoid eddy currents in the test specimen, which demagnetize
the test specimen and lead to a too low coercivity. The magnetizing field decay from magnetic
saturation to zero shall be adjustable between 1 s and 40 s, depending on the magnetic
permeability, electrical conductivity and thickness of the test specimen.
9.2 Measuring methods
9.2.1 General
Two methods, A and B, can be used for the detection of a state of zero magnetic polarization
in the test specimen during the demagnetization.
The magnetic field strength in the solenoid shall be measured with an accuracy equal to or
better than ±0,5 %.
9.2.2 Method A
This method is based on the use of either:
a) a magnetic flux sensing probe with a Hall probe placed near the end of the test specimen
with its measurement axis at 90° to the axis of the solenoid (see Figure 3). The Hall probe
shall be positioned off the axis and in the homogeneous region of the solenoid to give
good sensitivity for the stray magnetic field of the test specimen and to suppress the
sensitivity for the magnetic field of the solenoid at the same time, or

Key
1 solenoid
2 test specimen
3 Hall probe
Figure 3 – Method A, magnetic flux sensing probe: Hall probe

– 10 – IEC 60404-7:2019 © IEC 2019
b) a magnetic flux sensing probe with a differential fluxgate probe consisting of two single
fluxgate sensors connected in series opposition, placed inside the solenoid. The distance
between the fluxgate probes and the end of the test specimen is variable (see note
below), depending on the size and permeability of the test specimen (see Figure 4). This
is an integral measurement of the stray magnetic field divergence over the length of the
test specimen, where the distance between the test specimen and the fluxgate probes is
longer than the length of the test specimen. The distance between the test specimen and
the fluxgate probes is a reasonable compromise between signal strength and the integral
stray magnetic field measuring effect. By this differential method, the influence of uniform
external magnetic fields is amply compensated for.
NOTE Practical experience in the measurement of very small and/or very soft magnetic materials determine the
distance between the fluxgate probes and the test specimen of between 10 mm and 40 mm.
Magnetic flux sensing probes which measure the stray magnetic field of the test specimen at
a very small distance from the test specimen, set limitations on the test specimen geometries.
These systems have errors which are relevant to the shapes of the test specimen which are
different from ellipsoids (see Figure 6) and to non-uniform magnetic properties over the
volume of the test specimen.
Key
1 solenoid
2 test specimen
3 differential fluxgate probe consisting of two single fluxgate sensors connected in series opposition
Figure 4 – Method A, magnetic flux sensing probe: differential fluxgate probe
9.2.3 Method B
This method is based on the use of a differential fluxgate probe consisting of two single
fluxgate sensors, connected in series opposition, placed outside the solenoid. This is an
integral measurement of the stray magnetic field of the test specimen (see Figure 5).

Key
1 solenoid
2 test specimen
3 differential fluxgate probe consisting of two single fluxgate sensors connected in series opposition
Figure 5 – Method B, magnetic flux sensing probe: differential fluxgate probe
By this differential method, the influence of uniform external magnetic fields is amply
compensated for. The axis of the differential fluxgate probe is positioned at 90° to the
magnetic field of the solenoid to measure only the stray magnetic field of the test specimen.
The large distance between the two single fluxgate sensors and the test specimen requires a
high sensitivity of the fluxgate probes, usually 0,5 nT. They measure the integral of stray
magnetic field divergence over the length of test specimen. The same condition applies to the
magnetic inhomogeneity over the volume of the test specimen.
9.3 Determination of coercivity
The solenoid, in which the test specimen is placed, is connected to a variable DC current
supply. The test specimen is magnetized to saturation and then the magnetic field is reduced
smoothly without interrupting to zero. The demagnetizing current through the solenoid shall be
increased continuously and slowly to the point at which no stray magnetic field of the test
specimen is detected.
The value of this demagnetizing current shall be measured with a digital voltmeter connected
across a shunt resistor (see Figure 2) giving an accuracy equal to or better than 0,5 %.
The current shall be measured for each of the two directions of the demagnetizing field of the
solenoid.
The value of the coercivity shall be calculated from the relationship:
H = kI
cJ
(2)
where
H is the coercivity, in amperes per metre (A/m);
cJ
I is the mean value of the two currents of opposite polarity, in amperes (A);
k  is magnetic field strength to current ratio for the solenoid, in per metre (1/m).

– 12 – IEC 60404-7:2019 © IEC 2019
When method A is used, the measurement shall be made for each end of the test specimen,
the value of the coercivity being taken as the mean of the two measurements. Test specimens
which have a non-ellipsoidal shape or with inhomogeneous magnetic properties shall
generally be measured at each end.
For materials having a coercivity greater than 1 kA/m, it is not necessary to make
measurements for two directions of the magnetic field.
NOTE Method A is a localized measurement whereas Methods B and C (see Annex B) are integrated
measurements. Therefore the results cannot be the same for a magnetic inhomogeneous test specimen or for a
test specimen which has a non-ellipsoidal shape (see Figure 6).

Key
1 magnetic polarization J is zero at the ends of the rod; corresponding to Method A with local flux
measurement
2 sum of the magnetic polarization J is zero over the length of the rod; corresponding to Method B and C with
integral flux measurement
3 magnetic polarization J is zero at the centre of the rod
4 the test specimen as a cylindrical rod
Figure 6 – Magnetic polarisation J over the length L of a cylindrical rod
9.4 Reproducibility
Provided the foregoing procedures are carried out and the material has a uniform magnetic
polarization, the reproducibility of the determination of the coercivity normally expected is less
than:
– ±10 % for coercivities from 0,2 A/m up to 5 A/m;
– ±5 % for coercivities up to 50 A/m;
– ±2 % for coercivities up to 1 kA/m;
– ±1 % for coercivities up to 160 kA/m.
However, this reproducibility can be affected by non-uniform magnetic properties and the non-
ellipsoidal shape of the test specimen.

10 Test report
The test report shall contain, as necessary:
– type and condition of the material;
– the shape and dimensions of the test specimen;
– the method of magnetizing to saturation;
– the measuring method and device used;
– the calculated value of the coercivity H ;
cJ
– the test temperature;
– the date of the test.
– 14 – IEC 60404-7:2019 © IEC 2019
Annex A
(normative)
Precautions to be taken for measurements of coercivity below 40 A/m,
with a complex shaped test specimen and some special cases

A.1 Coercivity below 40 A/m
For materials having a coercivity below 40 A/m, the following precautions shall be observed:
a) the measuring apparatus shall be set up in an environment free from strong magnetic
fields and remote from masses of magnetic material;
b) the ambient magnetic field shall be compensated for or the equipment shall be shielded to
reduce the value of the field to below 0,5 A/m;
c) care shall be taken to avoid the introduction of internal mechanical stresses during and
after preparation of the test specimens;
d) when using a Hall probe to measure coercivity below 10 A/m, it shall be checked that the
magnetic field due to the Hall probe bias current does not affect the measurement.
A.2 Coercivity measurement of test specimens with complex shapes
The measurement of a complex shaped test specimen, different from ellipsoids, is only
possible with an integral measurement according Method B. The influence of the complex
shape on the coercivity can be further minimized by using the mean value from the two
coercivity measurements on both ends of the test specimen.
A.3 Optimization of the amplitude and time of the magnetizing cycle for a test
specimen of soft magnetic material
These two parameters can be optimized as a too high a magnetization amplitude heats up the
solenoid and a too short a time produces eddy currents in the test specimen with high
electrical conductivity.
The procedure of the optimization can be as follows:
Gradually reduce the magnetization amplitude from 200 kA/m to approximately 25 kA/m in
decrements of 10 kA/m and perform an H measurement at each step at a constant
cJ
magnetization time of 40 s. If the H value drops by more than 2 %, the minimum value for
cJ
the magnetization amplitude is achieved. To guarantee the state of saturation, the determined
minimum magnetization amplitude should be increased by 20 %.
Reduce the magnetization time from 40 s to 1 s in decrements of 5 s to 10 s and perform an
H measurement at each step to the previously determined minimum magnetization
cJ
value drops by more than 2 %, the minimum value for the
amplitude (+20 %). If the H
cJ
magnetization time is achieved. To obtain an optimized state of test, the determined minimum
magnetization time should be increased by 20 %.
A.4 Mechanical stress and heating of the test specimen in the solenoid
During the measurement the test specimen shall not be stressed either mechanically or
thermally since both may change the coercivity. The temperature of the test specimen shall be
maintained within 23 °C ± 5 °C during the measurement of coercivity. If the test specimen
becomes heated in the solenoid, it shall be air cooled in the solenoid.

Annex B
(informative)
Method C with a VSM (Vibrating Sample Magnetometer)

The Method C with a VSM (Vibrating Sample Magnetometer) [5], [6] is used for the
measurement of the coercivity of magnetic materials in an open magnetic circuit. The
difference between Method A and Method B is the magnetizing circuit. Instead of a solenoid
an electromagnet with yokes is used and the measuring range of the coercivity is limited to a
minimum of 2 kA/m.
In a VSM, a test specimen is located within suitably placed search coils, and is made to
undergo sinusoidal motion, i.e., mechanically vertical vibrated. The resulting magnetic flux
variations induce an alternating voltage in the search coils that is proportional to the magnetic
moment of the test specimen. The magnetic field is generated by an electromagnet [5], [6].
The magnetic field at which zero alternating voltage, induced in the search coils by the
polarization of the test specimen, is detected (see Figure B.1), represents the coercivity of the
sample.
The VSM should be calibrated with a known standard test specimen of the same size and
shape as the test specimen to be measured.

Key
1 search coils
2 vertical vibrating test specimen holder
3 electromagnet pole pieces
4 test specimen
Figure B.1 – Schematic diagram of Method C with a VSM

– 16 – IEC 60404-7:2019 © IEC 2019
The measurement with the VSM is an integral measurement of the stray magnetic field of the
test specimen, when the volume of the test specimen is in the homogeneous region of the
search coils and in the centre region of the search coils. The VSM is only applicable to small
test specimens (e.g. 5 mm x 5 mm x 5 mm).

Bibliography
[1] Rainer Hilzinger, Werner Rodewald, Magnetic Materials – Fundamentals, Products,
Properties, Applications -, VAC 2013, ISBN-10: 3895783528
[2] H. Czichos, T. Saito, L. Smith, Springer Handbook of Materials Measurement Methods,
[3] EN 10330-2015: Method of measurement of the coercivity of magnetic materials in an
open magnetic circuit
[4] Heiko Ahlers, Design of transversal earth magnetic field compensating coil systems
and their comparision with conventional systems, PTB -Mitteilungen 109, pp. 131-137,
[5] S. Foner, Versatile and Sensitive Vibration-Sample Magnetometer, vol.30, no.7,
pp. 548-557, 1959
[6] IEC TR 62797, International comparison of measurements of the magnetic moment
using vibrating sample magnetometers (VSM) and superconducting quantum
interference device (SQUID) magnetometers

___________
– 18 – IEC 60404-7:2019 © IEC 2019
SOMMAIRE
AVANT-PROPOS . 19
1 Domaine d'application . 21
2 Références normatives . 21
3 Termes et définitions . 21
4 Principe de la méthode . 23
5 Eprouvette d'essai . 24
6 Solénoïde . 24
7 Compensation du champ magnétique terrestre et des champs magnétiques
parasites statiques et dynamiques . 24
8 Blindage magnétique de la zone de mesure . 24
9 Mesurage . 25
9.1 Aimantation . 25
9.2 Méthodes de mesure . 25
9.2.1 Généralités . 25
9.2.2 Méthode A . 25
9.2.3 Méthode B . 27
9.3 Mesurage de la coercitivité . 27
9.4 Reproductibilité . 28
10 Rapport d'essai . 29
Annexe A (normative)  Précautions à prendre pour le mesurage de la coercitivité au-
dessous de 40 A/m, avec une éprouvette de forme complexe et certains cas
particuliers. 30
A.1 Coercitivité au-dessous de 40 A/m . 30
A.2 Mesurage de la coercitivité des éprouvettes de formes complexes . 30
A.3 Optimisation de l'amplitude et du temps du cycle d'aimantation pour une
éprouvette du matériau magnétique doux . 30
A.4 Contrainte mécanique et échauffement de l'éprouvette dans le solénoïde . 31
Annexe B (informative) Méthode C avec un VSM (magnétomètre à échantillon vibrant) . 32
Bibliographie . 34

Figure 1 – Courbes de désaimantation B(H) et J(H) depuis la saturation . 22
Figure 2 – Schéma du circuit pour les Méthodes A et B . 23
Figure 3 – Méthode A, sonde sensible au flux magnétique: sonde de Hall . 26
Figure 4 – Méthode A, sonde sensible au flux magnétique: sonde différentielle de flux
à seuil . 26
Figure 5 – Méthode B, sonde sensible au flux magnétique: sonde différentielle de flux
à seuil . 27
Figure 6 – Polarisation magnétique J sur la longueur L d'une tige cylindrique . 28
Figure B.1 – Schéma de la Méthode C avec un VSM . 32

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
MATÉRIAUX MAGNÉTIQUES –
Partie 7: Méthode de mesure de la coercitivité (jusqu'à 160 kA/m) des
matériaux magnétiques en circuit magnétique ouvert

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