Transverse field anneal studies of high moment FeCoB and FeCoZr films

Ever increasing areal densities have driven the need for high moment materials with large saturation magnetizations greater than 2 T. In addition, for applications such as write poles and soft underlayers, the high moment materials must exhibit soft and uniaxial magnetic properties which are thermally stable during high temperature processing. In this work, we examine 2.1 T FeCoB and 1.8 T FeCoZr films which are amorphous in the as-deposited state. The films are given longitudinal field anneals (LFAs) at 220 and 250 °C for 4 h. FeCoZr films remain amorphous after the 220 and 250 °C LFAs. FeCoB films remain amorphous after the 220 °C LFA, however, the 250 °C LFA results in crystallization in the FeCoB film. This crystallization is accompanied by a degradation in soft magnetic properties. As-deposited and 220 and 250 °C LFA FeCoB and FeCoZr films are then given transverse field anneals (TFAs) at 150 °C. As-deposited FeCoB and FeCoZr experience a 90° rotation of Hk or switching after less than 2 h of TFA. LFAs result in improved thermal stability in all FeCoB and FeCoZr films. The crystalline FeCoB film given a 250 °C LFA exhibited the best thermal stability, however, the magnetic properties were not optimal due to crystallization.