Temperature dependence of intrinsic magnetic hardness in some rare-earth pseudobinary compounds and amorphous materials

Predictions of the thermal activation equation for coercivity H/sub c/(T) = H0(- V/s T/T + (1 + (V/sub T/T)2)/sup 1/2/) are compared with literature data on SmCo/sub 2.5/Ni/sub 2.5/, LaCo2Ni3, and amorphous TbFe2. In the first two cases, much better agreement is obtained by forcing H0 (coercive force in the absence of domain wall activation) and V/sub T/ (activation parameter) to vary according to the temperature dependence of ionic parameters relating to anisotropy, exchange, and magnetization. For LaCo2Ni3, no additional free parameters are introduced into the activation equation. For SmCo/sub 2.5/Ni/sub 2.5/, a small additive temperature independent coercivity may be necessary. By contrast, H/sub c/(T) in amorphous TbFe2 is shown to imply temperature independence of the ionic parameters. The activation equation is shown to be equivalent to an empirical, exponential relationship for H/sub c/H0 >= 0.4, and also at smaller values if the ionic parameters vary suitably with temperature. Thus, in a given pseudobinary series at low temperature, we find H/sub c//H0 approximately e/sup -bdeltaT/T/sub c/, with delta the domain wall thickness and b a constant. (author)