Difference between temperature dependences of both initial permeability and maximum permeability of sendust alloys

The temperature dependences (-10-50°) of the initial permeability (μ5), the maximum permeability (μmax), and the coercive force(Hc) of Sendust alloys (Fe-9 to 10 wt% Si-5 to 7 wt% Al) continuously cooled to room temperature, were investigated. Most of the studied alloys gave at least one peak value for both μ5and μmax, in the studied temperature range. The temperature giving the peak μ5agreed well with that of μmax(an effective permeability at an alternating field): the peak temperature of μeffseems to correspond to the temperature giving a zero magnetocrystalline anisotropy constant (K1= 0). The relationship between temperature and μ5was not always the same as that between temperature and μmax. From the compositional dependence of μmaxat various temperatures (10-30°C), the zero polycrystalline magnetostriction constant (λs = 0) line of the ternary Sendust alloys at each temperature could be evaluated. It is clarified that μ5of the alloys with K1< 0 is determined by both K1and λs, whereas μmaxis primarily determined by λs. When K1changes with temperature from a negative to a positive value, both μ5and μmaxof the alloys markedly decrease, independently of λs.