SU1288638A1 - Method of measuring coercive force of ferromagnetic materials - Google Patents

Abstract

This invention relates to a magneto measuring technique. The purpose of the invention is to increase the measurement accuracy. In sample 1, which is influenced by the magnetic field of the source 3 of the magnetizing field and the connecting unit 2, the acoustic wave propagates by the RF generator 7 and the electroacoustic converter 5. The magnetic field changes the velocity of the acoustic wave and changes em its phase. H This change in the frequency of the signal in the absence of a field is proportional to the square of the magnetization of sample 1. The absolute change of the phase of the elastic wave is measured as a function of the magnetic field strength determined by gauge 4 when magnetized to saturation and further demagnetized of sample 1 according to the hysteresis curve f) it is possible to measure its coercive force N. 1 3. p. fl, 2 ill. S s5 oo o :) oo PuZ.t

Description

This invention relates to a magnetometer and is intended to measure the coercive force of magnetic materials, in particular thin magnetic films, in both open and closed magnetic circuits,

The purpose of the invention is to pick up precise FiocTH measurements.

FIG. 1 is a diagram of a device for measuring the goat strength of magnetic materials; FIG. 2- sensitive element of the device for measuring the coercive force of thin magnetic films.

The device contains the test sample 1, placed in the magnetizing unit 2 with the source 3 of the magnetizing current. The intensity of the magnetic field is monitored by meter 4. Electro-acoustic transducers (HALL) 5 and 6 are located at the edges of sample 1 to excite and receive elastic waves. Converter 5 is connected to the RF generator 7 and to the meter 8 phase difference through an attenuator 9. Converter 6 is connected to the meter 8 phase difference 8.

Electro-acoustic transducers are applied onto test sample 1, consisting of a substrate 10 (Fig. 2) with test film 1 deposited on it from a magnetic material.

5 and 6 for the excitation of surface 35 space at a frequency of

in a film of iron yttrium garnet grown on a plate of gallium gadolinium garnet with dimensions of 10 x X 10 X 0.8 mm, can be achieved with a value of a magnetic field of 8-10 Oe. It follows that the absolute phase change of 0.5 ° body and surface waves, performed, in contrast to those shown in FIG. 1 interdigital.

The method is carried out as follows.

The magnetic field created by source 3 and magnetizing unit 2 affects sample 1, in which the acoustic wave generated by RF generator 7 and EAP 5 due to the de-effect propagates, leading to a change; wave speed, and, consequently, to the measurement of its phase-C, measured by the meter 8 by the signal from the EAS. 6, and the reference signal coming through the attenuator 9 from the output of the RF generator 7. This is a wave of acoustic waves propagating in various materials at frequencies of 100 MHz in magnetic fields with a intensity of only 10–20 E. that if in the studied magnetic materials elastic elastic waves can propagate at frequencies at which the attenuation of a wave in this material allows

H - H, where

H d phase

change

the signal in the absence of a field is proportional to the square of the sample magnetization. The dependence of the absolute change in the phase of the elastic wave on the strength of the magnetic field determined by measuring device 4 with magnetization until it is saturated and further demagnetization of the sample under study is measured by the hysteresis curve H (N). You can measure its coercive force H ,.

It is obvious that the absolute zero phase change (- 4,) of an acoustic wave corresponds to zero, the magnetic state of the sample, when

ten; H N J ,. In this case, meter 4 shows the value of the coercive force AND t of sample 1. Attenuator 9 equalizes the amplitudes of the delayed and reference signals, which is necessary for normal operation of the phase difference meter.

To study the thin magnetic films 1 deposited onto the substrate 10 (Fig. 2), it is more expedient to use surface acoustic waves propagating directly in the films, which makes it possible to increase the accuracy of measurements of the coercive force of thin magnetic films. In this case, electroacoustic transducers 5 and 6 are made interdigital (Fig. 2). The existing phase-measuring equipment makes it possible to measure the absolute change in the phase of the elastic wave to O, 5. It has been experimentally proven that such a phase change, for example, a surface acoustic wave, is

five

0

in a film of iron yttrium garnet grown on a plate of gallium gadolinium garnet with dimensions of 10 x X 10 X 0.8 mm, can be achieved with a value of a magnetic field of 8-10 E. In addition, from literature data for magnetic materials It follows that the absolute phase change of 0.5 ° bulk and surface acoustic waves propagating in various materials at frequencies j 100 MHz is achieved in magnetic fields with a strength of only 10-20 Oe. This means that if in the studied magnetic materials can be spread elastic acoustic waves at frequencies at which the damping of a wave in a given material allows

you can confidently receive a delayed signal, then you can take the corresponding hister € 1 curves and, therefore, with high accuracy on31

Determine the coercivity of various magnetic materials, in particular thin magnetic films.

Claims (2)

1. A method for measuring the coercive force of ferromagnetic materials, including excitation of an acoustic wave in a test sample and magnetization of a sample in a magnetic field, characterized in that, in order to improve measurement accuracy, the excitation of acoustic waves is carried out in continuous mode. eight press, record the phase change of the transmitted acoustic wave depending on the magnetic field strength and at the moment when the absolute value of the phase change of the acoustic wave reaches zero, when the sample is magnetized in the opposite direction, the coercive force value is recorded. 2. A method according to claim 1, of tl and h aa-yu, and with the fact that in the film under study, surface acoustic waves are excited by the composite sound conductor method.  0 figg Editor A. Shandor Order 7804/44 Compiled by M. Bukharov Tehred M. Khodanich Proofreader S. Shekmar Circulation 752 Subscription VNIIPI USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Raushsk. About. 4/5 Production and printing company, Uzhgorod, st. Project, 4