The roles of steady and alternating fields playing in the anhysteretic process

Abstract

Summary It is incorrect to think that anhysteretic remanent magnetization (ARM) is produced by the steady (DC) field and that the role of the alternating field is to enable domain walls to overcome energy barriers in multidomain (MD) grains and to decrease the potential energy barrier that prevents rotation of the magnetic moments in single domain (SD) grains. The alternating field (Hac) produces an isothermal remanence in the sample during every half-cycle. When no DC field (Hdc) is superimposed, the residual remances acquired during successive positive and negative half-cycles cancel out. The effect of a superimposed DC field is to bias the remanences acquired during positive and negative half-cycles, resulting in a net remanence in the direction of the steady field (for the isotropic case). It is the total alternating field, not the DC field, that is responsible for imparting the ARM, and the coercivity of grains affected is determined accordingly. In order to perform a detailed analysis, cases of Hdc= 0, d > 2Hdc, d=2Hdc, and d < 2Hdc are examined (d is the amplitude decay per half-cycle of Hac) by the switching-field model. The total residual remanence is dependent on decay rate, Hdc and Hac when Hdc < d/2, but independent of Hdc when Hdc≥d/2