BS EN IEC 60404-18:2025

Magnetic materials. Permanent magnet (magnetically hard) materials. Methods of measurement of the magnetic properties in an open magnetic circuit using a superconducting magnet | Status: Current

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:

1. — the SCM-vibrating sample magnetometer (VSM) method;
2. — 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.