High-temperature magnetic behavior of soft/soft and soft/hard Fe and Co-based biphase microwires

The magnetic behavior of biphase magnetic microwires has been investigated in the high-temperature range from 295 to 1200 K. Bimagnetic microwires consist of a magnetically soft amorphous core (i.e., positive, FeSiB, and negative, CoFeSiB, magnetostriction alloy) and external polycrystalline shell with soft (FeNi, Permalloy) and medium-hard (CoNi) magnetic character. The magnetic phase transitions (ferro to paramagnetic) of individual phases are first detected through the temperature dependence of magnetization where structural changes in the amorphous alloy cores are also identified. Moreover, the values of coercive field of individual and bimagnetic phase systems are analyzed in view of these magnetic and structural transitions. The study is relevant for technological applications of bimagnetic microwires in the temperature regime above room temperature. (C) 2014 AIP Publishing LLC.