抄録
A magnetic particle with a coercivity control layer (CCL), which stacks a hard magnetic region and a soft magnetic region, can create a lower coercivity than a conventional magnetic particle without a soft magnetic region. In this paper, the coercivity reduction mechanism is considered from the viewpoint of magnetic torque, and it is found that the exchange interaction between the hard region and the soft region assists the magnetic switching in the hard region, and that the magnetic torque due to magnetic anisotropy is decreased by the formation of a non-uniform magnetization configuration in the hard region. The thermal stability of a magnetic particle with a CCL is found to be less than that of a conventional magnetic particle with the same anisotropy constant but more than that of a conventional particle with the same coercivity. As a result, a thin-film medium that comprises magnetic particles with a CCL can be used as a recording medium without damaging the thermal stability. Moreover, it is found that incoherent magnetic reversal takes place at a finite temperature for a magnetic particle, even though its reversal mechanism is coherent at 0 K.
