Effects of Annealing Treatment on Low and High Frequency Magnetic Properties of Soft/Hard Biphase FeSiB/CoNi Microwires

Soft amorphous Fe₇₆Si₁₃B₁₁ microwires were fabricated by Taylor-Ulitovsky technique and an external Co₉₀Ni₁₀ shell with magnetically harder behavior was additionally grown by combined sputtering and electro-plating techniques. The effect of annealing treatment at temperatures up to 700^°C for 1 h on low-frequency coercivity and the ferromagnetic resonance, FMR, frequency for single and biphase microwires was investigated. The properties after low temperature annealing (up to 500 ^°C) are reasonably maintained, which indicates the suitability of these families of wires for sensing applications up to relatively high temperatures. Nevertheless, low and high frequency properties are significantly deteriorated after crystallization of the amorphous core. FMR behavior was analyzed by fitting to Kittel equation for annealed samples. The observed different absorption peaks are correlated with the presence of the soft core and the external shell.