Coercivity analysis in sputtered Sm-Co thin films

Hard nanocrystalline Sm-Co thin films having a thickness of 500 nm have bee n prepared by heat-treating magnetron sputtered amorphous samples deposited over a 300 nm Cr buffer layer onto room temperature water cooled Si substr ates. The thermal treatments resulted in the nanocrystallization of the pre cursor films and in the development of room temperature coercivities coveri ng a range going from a few kOe, measured in the samples treated at low tem perature, up to some tens of kOe, observed in the case of the films anneale d at high temperatures (the room temperature coercivity of the sample treat ed at 825 K was 26 kOe). Our analysis of the influence of the thermal treat ments on the particularities of the reversal process was based on the measu rement of the temperature dependence of the coercive force. It was carried out in the framework of the micromagnetic model, which allowed us to evalua te two parameters accounting for the local anisotropy reduction and the mag nitude of the local dipolar fields, respectively. Our results show that the high temperature treatments result in a better degree of crystallization ( lower local anisotropy deterioration). That crystallinity improvement is as sociated to an increase of the local dipolar interactions. (C) 1999 America n Institute of Physics. [S0021-8979(99)68808-9].