Giant intrinsic magnetic hardness in SmCo5−xCux

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Abstract
The system SmCo5−xCux was studied with respect to constitution and magnetic properties, focusing on the mechanism of magnetization. Different modes of preparation result either in single‐phase or in multiphase materials as determined by x‐ray diffraction. Pseudobinary materials show giant intrinsic magnetic hardness irrespective of mode of preparation. The temperature dependence of coercive force (Hc) is in accordance with a model based on thermally activated domain‐wall propagation. Maximum values of Hc extrapolated to absolute zero are the highest for any material so far reported (of order Hc=300 kOe). These values are slightly greater than the maximum in SmCo5−xNix. It is found that a local moment picture predicts relative magnitudes of both magnetic moment and coercivity as a function of composition. Accordingly coercivity is dependent on the number of weakly coupled transition metal atoms.