Thermal effects on delta-M measurements in magnetic thin films

Thermal effects on delta-M curves have been studied in a series of CoCrPtB thin films. Film thicknesses ranged from 5 mn to 50 mn and KuV/k(B)T values ranged from 29 to 132. Delta-M curves were measured as a function of field step, wait time at each field step, and measuring conditions. If dc-demagn etization remanence (DCD) curves are measured by applying a saturating fiel d before each reverse field, then the delta-M curves depend on field step f or all films and on wait time for the film with the smallest KuV/k(B)T. At small field steps, the field step dependence is approximately logarithmic a nd the rate is approximately the same as the remanent viscosity coefficient . If a saturating field is applied only at the beginning of the DCD measure ment sequence, the field step and wait time dependences are essentially eli minated. For fixed field step and waiting time, the area under the delta-M curve normalized to the remanent coercivity increases linearly with k(B)T/K uV when the repeat saturation method is used. The dependence on k(B)T/KuV i s largely eliminated if there is no repeat saturation field.