The influence of external magnetic field and femtosecond laser pulses on the anomalous Kerr loops in GdFeCo amorphous film

The anomalous loops obtained by applying the traditional Kerr loop technique, in which the sample was pumped by continuous pulses using the method of successive increment scanning external magnetic field, contained memory and accumulation effects originating, respectively, from external field history and multiple pulse excitations. To eliminate the memory effect and study the influence of external magnetic field on the anomalous loops, an initializing field scanning approach was used to replace the method of successive increment scanning external field. And to confirm the existence of accumulation effect and study the influence of pump pulses on the anomalous loops, a controllable pump-pulse-number magneto-optical Kerr technique was used to replace continuous pulses pump Kerr technique. In both ways, measured with different pump fluence and different pump pulses, the results showed clearly the dependence of the hot coercivity and the degree of magnetization reversal on the external field, pump pulse numbers and pump fluence.