Thermal Stability of Field- and Stress-Induced Anisotropy in Nanocrystalline Fe-Based and Amorphous Co-Based Alloys

Abstract

Thermal stability of induced magnetic anisotropy (IMA) was studied in a course of subsequent annealings without any external effects for already field- or stress-annealed specimens of the nanocrystalline Fe_73.5Cu₁Nb₃Si_13.5B₉ and amorphous Fe₃Co₆₇Cr₃Si₁₅B₁₂ alloys. For these alloys the dependence of IMA thermal stability on the magnitude of the IMA constant (K_u) and temperature of stress-annealing was investigated. For the nanocrystalline alloy thermal stability of field- and stress-induced anisotropy with identical K_u was compared. It was shown that nanocrystalline specimens with identical K_u values after field- or stress-annealing have identical thermal stability of IMA. This can point to a similarity of the mechanisms of IMA formation after field- or stress-annealings. Thermal stability of stress-induced anisotropy in the nanocrystalline alloy with K_u value less than 1000 J/m₃ and the amorphous alloy with K_u less than 100 J/m³ depends on the value of K_u. For both stress-annealed nanocrystalline and amorphous alloys magnetic anisotropy induced at higher temperatures is more stable because more long-range and energy-taking processes take place at these temperatures.