Magnetic Properties of Glass-Coated FeWB Microwires

We have studied magnetization process in amorphous bistable $Fe_{80}W_{3}B_{17 }$ microwires with reduced Curie temperature. High mechanical stresses from glass-coating, induced during production process, result in high switching field. Reducing the length of microwire, the switching field decreases as a result of reduction of magnetoelastic anisotropy. Moreover, the decrease of magnetoelastic anisotropy results in a complex temperature dependence of the switching field. On the other hand, strong variations of the switching field with temperature can be employed in miniaturised temperature sensor

Temperature microsensor/microactuator based on magnetic microwire for MEMS applications

The aim of this paper has been the development of a new type of temperature microsensor/microactuator working on the principle of the thermo-elastic (TE) deformation of multilayer magnetic microwire consisting of a glass-coated CoSiB metallic core and an electroplated CoNi external shell. The application of an electrical current along the microwire in the range 20-35 mA results in the TE mechanical bending of fixed sample, which is recorded. That mechanical deformation is interpreted to be a consequence of the resulting Joule heating, and its amplitude is directly proportional to the applied dc current in the mentioned range. Moreover, the direct proportionality between TE deformation and the resulting increase of temperature was experimentally confirmed. In this way, the new type of temperature microsensor/microactuator working on the principle of TE deformation has been developed. This opens new technological application of microwires as temperature microsensors and temperature-driven microactuators for micro-electro-mechanical system devices

Magnetic properties and magnetoimpedance of short CuBe/CoFeNi electroplated microtubes

The magnetic properties and, particularly the magnetoimpedance, MI, of short CuBe/CoFeNi electroplated microtube, 0.9–1.7 cm long, consisting of a CuBe metallic core surrounded by an electroplated ferromagnetic CoFeNi shell have been investigated with the final aim to be used as sensitive elements in sensor devices. From the analysis of the experimental hysteresis loops, we confirm the presence of a circular magnetic anisotropy of the ferromagnetic shell and the significant role of the inhomogeneous local distribution of the magnetization near the ends of the microtube. It is experimentally observed that the maximum MI ratio and its ohmic component depend very significantly on the microtube length while particularly the maximum value of the ohmic component is higher than that of the total MI ratio for all selected samples. These maxima are different from each other: the value of (ΔZ/Z), (ΔR/R), the MI sensitivity, and the value of the field in which each particular MI appears. Interesting MI behavior was observed in the low excitation frequency of 2.5 MHz, where the length dependence of operation frequency was also studied. An optimal response is obtained for intermediate (critical) length sample with reduced border effect. This fact makes electroplated microtubes attractive for magnetic conditions devices and other applications.This work was performed in part under financial support The Ministry of Education and Science of the Russian Federation, project ➓ 1362

Magnetic Properties of CoFeSiB/CoNi, CoFeSiB/FeNi, FeSiB/CoNi, FeSiB/FeNi Biphase Microwires in the Temperature Range 295-1200 K

We have studied the magnetic properties of two series of magnetically biphase microwires with 1 μm thickness of CoNi-based hard or FeNi-based soft shells with a core of FeSiB or FeCoSiB glass-coated microwires. The magnetic properties were analyzed as a function of temperature in the range from 295 K to 1200 K using a vibrating sample magnetometer. Analysis of the magnetization reversal of each phase with measuring temperature has been performed