A survey of anisotropy measurement techniques and study of thickness effect on interfacial and volume anisotropies in Co∕Pt multilayer media

A survey of various measurement techniques, including the rotation method, the hard-axis hysteresis loop, and the torque measurement, is presented using Co∕Pt multilayer recording media. It is found that for highly exchange-coupled samples, the results from the rotational method are consistent with those from the hard-axis hysteresis loop and torque measurements. Such anisotropy measurements are applied to determine the interfacial anisotropy in Co∕Pt multilayers (MLs) by studying a series of Co∕Pt ML samples with Co thickness ranging from 0.1 to 2 nm. The Pt thickness is fixed at either 1 or 0.5 nm. It is found that the multilayer with 1 nm Pt layer shows a larger interfacial anisotropy constant (KS∼0.8erg∕cm2) than the media with 0.5 nm Pt layer (KS∼0.6erg∕cm2), corresponding to about 80% and 60% of the interfacial anisotropy of the ML made by molecular-beam epitaxy, respectively [D. Weller et al., Mater. Res. Soc. Symp. Proc. 313, 791 (1993)]. Such thickness dependence is supported by the x-ray-diffraction superlattice peak measurements that indicate the discontinuous growth for the case with thinner Pt.