MAGNETIZATION AND COERCIVITY STUDIES IN AMORPHOUS ND50FE50 BN MULTILAYERS/

Amorphous Nd50Fe50/BN multilayers were fabricated by sputtering over a wide range of bilayer thickness. A superparamagnetic behavior was fou nd above 20K in samples with a d(NdFe) thickness below 15 angstrom whi ch maybe due to the particulate like nature of the thinner films. In s amples with d(NdFe) above 15 angstrom, the spontaneous magnetization w as found to be independent of thickness. The coercivity increases with the NdFe layer thickness according to 1/d(NdFe) and this may be relat ed to the out of plane effective surface anisotropy. The spontaneous m agnetization doesn't follow Bloch's law above 50K. Instead a linear te mperature dependence is observed in the temperature range of 50 - 300K , with the temperature range extending to lower temperature in samples with thinner NdFe layers.