Магнитострикция пленок граната (YSmLuCa)-=SUB=-3-=/SUB=-(FeGa)-=SUB=-5-=/SUB=-O-=SUB=-12-=/SUB=- методом низкочастотной восприимчивости

Certification of new magnetic materials requires high-precision nondestructive methods. The method of measuring the magnetostriction constant of films by studying low-frequency magnetic susceptibility at elastic deformation of the films is proposed. The method allows a tenfold improvement of the accuracy of measurements of the magnetostriction constant as compared with the methods applied earlier.

High Temperature Properties of CoFe/CoNi and Fe/CoNi Biphase Microwires

The objective of this work has been to analyze the high-temperature behavior of magnetically single-and biphase microwires because of its interest from fundamental and applications viewpoints. Two alloy compositions with amorphous structure covered by glass have been prepared as magnetically single phase microwires by quenching & drawing technique: CoFe-based with near zero saturation magnetostriction constant and Fe-based with positive saturation magnetostriction constant. The same wires were used as the core for magnetically biphase microwires. Second CoNi phase was deposited by electroplating. Magnitudes as saturation magnetization and hysteresis parameters are determined in the temperature range from room temperature up to 1200 K. We proceed to a comparative analysis of their magnetic behaviour at different temperatures as well as after cooling down to room temperature. Information on the Curie temperature of different phases and on the influence of heating process on the magnetic properties is thus derived.

Effect of Thickness on Mechanically Tunable Magnetic Anisotropy of FeGa Thin Films Deposited on Flexible Substrates

A practical way to manipulate the magnetic anisotropy of magnetostrictive FeGa thin films grown on flexible polyethylene terephthalate (PET) substrates is introduced in this study. The effect of film thickness on magnetic properties and magnetostriction constant of polycrystalline FeGa thin films was investigated. The anisotropy field Hk of flexible FeGa films, i.e., the saturation field determined by fitting the hysteresis curves measured along the hard axis, was enhanced with increasing the tensile strain applied along the easy axis of the thin films, but this enhancement via strain became unconspicuous with increasing the thickness of FeGa films. In order to study the magnetic sensitivity of thin films responding to the external stress, we applied different strains on these films and measure the corresponding anisotropy field. Moreover, the effective magnetostriction constant of FeGa films was calculated from the changes of both anisotropy field and external strain based on the Villari effect. A Neel’s phenomenological model was developed to illustrate that the effective anisotropy field of FeGa thin films was contributed from both the constant volume term and the inverse thickness dependent surface term. Therefore, the magnetic properties for the volume and surface of FeGa thin films were different, which has been verified in this work by using vibrating sample magnetometer (VSM) and magneto-optic Kerr effect (MOKE) system. The anisotropy field contributed by the surface of FeGa film and obtained by MOKE is smaller than that contributed by the film volume and measured by VSM. We ascribed the difference in Hk to the relaxation of the effective strain applied on the films with increasing the thickness of films.

Manipulation of Magnetic Properties and Domain Wall Dynamics in Amorphous Ferromagnetic Microwires by Annealing under Applied Stress

The effect of annealing under applied stress on magnetic properties of Co-based or CoFeNi-based glass-coated microwires was studied. It was found that CoFeNi-based microwires became bistable after annealing because of changing of magnetostriction constant sign, while Co-based microwires keep S-shape of hysteresis loop. The domain wall dynamics of microwires which became bistable was also investigated and it was shown that microwires with acquired bistability are more suitable for applications.

Magnetoimpedance of Amorphous Ferromagnetic CoFeSiB Ribbons in the Wide Temperature Range

The influence of the temperature, elastic tensile stresses and external magnetic field on the impedance of amorphous Co75Fe5Si4B16 ribbons was studied. It was observed that the character of the elastic tensile stresses influences the impedance and its changes in the external magnetic field are determined by a temperature of the ribbons. It was shown that changes of the stressimpedance character and magnetoimpedance temperature dependences were caused by a change in the sign of a magnetostriction constant with the temperature.

Stress Dependence of Switching Field during the Devitrification of Finemet-Based Magnetic Microwires

We have studied the influence of the thermal treatment on the stress dependence of the switching field during the devitrification of amorphous Fe73.5Cu1Nb3Si11.5B11 microwires. The non-destructive test (NDT) method based on the magnetization reversal of ferromagnetic materials is sensible to changes in microstructural characteristics and the stress state of the material. The stress dependence has been explained considering the magnetoelastic contribution to the switching mechanism which is modified applying the tensile stresses and changing the magnetostriction constant and strength of the internal stresses distribution through thermal treatments. We show that by properly setting a frequency during the measurement and adequate treatment of the sample, it is possible to vary the sensitivity, magnitude and stress dependence of the sample. Keywords: Magnetic bistability, glass-coated microwires, switching field, stress sensor

Temperature Field Analysis of Dispensing Jet Based on GMA

In the dispensing jet based on GMA,current in the coil produces a large amount of heat,which affects the glue viscosity and magnetostriction constant and other parameters, and so bringing about poor quality dots, therefore, it is necessary to analysis the transient temperature field of jet dispenser .This article mainly discusses the transient simulation of temperature field of jet dispenser by means of the MSC·MARC software, then in contrast with the experiment results to master the laws of temperature, so as to take appropriate control measures in future.