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

Abstract

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.

First-principles investigation of the very large perpendicular magnetic anisotropy at Fe|MgO and Co|MgO interfaces

“…Surprisingly large PMA values, up to 1 to 2 erg/cm 2 , have been reported, which are comparable or even larger than the PMA observed at Co|Pt or Co|Pd interfaces. 24,25 This result is quite general and has been observed in both crystalline (MgO) and amorphous (AlOx) barriers, using both natural or plasma oxidation. 26,27 The PMA could be dramatically improved under annealing, 10,28,29 and x-ray photoemission spectroscopy has demonstrated that the PMA could be correlated without ambiguity with the presence of oxygen atoms at the interface.…”

Rapid thermal annealing of FePt thin films

“…These loops were measured in two geometries: magnetic field is applied in the film plane and out of the film plane. From the area difference between the in‐plane and out‐of‐plane M – H hysteresis loops, the effective magnetic anisotropy, K eff , can be extracted . While an in‐plane easy‐axis of magnetization with K eff = (3.6 ± 0.4) × 10 6 ergs cm −3 is obtained for the as‐grown FePt film (A1 phase), which is given by shape anisotropy ( K S = 2 π = (3.4 ± 0.4) × 10 6 ergs cm −3 ), an annealing time of 5 s is already sufficient to turn the easy‐axis of the magnetization into the out‐of‐plane direction.…”

Laser-induced magnetization switching in films with perpendicular anisotropy: A comparison between measurements and a multi-macrospin model

“…The samples have a perpendicular anisotropy K with a value of 3.94ϫ 10 5 J / m 3 at room temperatures determined by the rotation method. 12 from which a grain size of 12 nm was estimated. Figure 2 shows a set of time-resolved measurements on the sample.…”