RE-TM antiferromagnetic coupling and laser induced ultrafast magnetization reversal dynamics in GdFeCo magneto-optical films

Abstract

The RE-TM antiferromagnetic coupling behavior and magnetization reversal dynamics in passing through the fermimagnetic compensation temperature (Tm) due to laser heating of GeFeCo films are investigated using femtosecond time-resolved pump-probe Kerr spectroscopy. Owing to sample temperature passing through Tm and hence the exchange of net magnetic moment carriers, an abnormal hysteresis loop is observed. The saturation magnetization difference between magnetization states above and below coercive field is found under a same direction of magnetic field, which reveals the incomplete rigid coupling between RE and TM sub-lattices in GdFeCo. A complete ultrafast magnetization reversal and recovery dynamic process is experimentally observed at the saturation magnetic bias on the sample with Al heat sink layer. Besides, by comparing magnetization reversal at saturation magnetic bias with magnetization recovery at remanence, it was found that the magnetic field applied externally does not affect the rate of domain nucleation and growth, but only their magnetization direction.