Atomic layer stacking structure and negative uniaxial magnetocrystalline anisotropy of Co100^|^minus;xIrx sputtered films

Abstract

The negative uniaxial magnetocrystalline anisotropy (Ku) was evaluated for various compositions of Co100-xIrx thin films with respect to the atomic layer stacking structure. Pure Co film fabricated at a substrate temperature (Tsub) of 600 C was found to have a positive Ku of 6.1×10 6 erg/cm 3 . With increasing x, the sign of Ku changed from positive to negative, and the negative Ku took a maximum value of -9.6×10 6 erg/cm 3 at around x = 20 at. % for films fabricated at Tsub = 600 C. Adding more Ir decreased the absolute value of the negative Ku which became 0 over x = 50 at. %. X-ray diffraction analysis and scanning transmission electron microscopy revealed that the atomic layer stacking structure of the Co100-xIrx films changed from -A-B-A-B-(hcp) to -A-B-C-A-B-C-(fcc) stacking with increasing Ir content. Moreover, Co80Ir20 grains were revealed to consist of 2 kinds of randomly located composition-modulated atomic layers, nearly pure-Co and pure-Ir layers, while Co and Co50Ir50 had disordered structures. In this paper, a new perspective on the atomic layered structure with superlattice diffraction, which is different from the conventional "ordered structure", is discussed.

Reduction of magnetic damping and isotropic coercivity and increase of saturation magnetization in Rh-incorporated CoIr system

“…The optimum Ru thickness is at 30 nm, where both the K u and M s are at their peak (figure 1(c)). However, the optimum percentage of Ir presented here should not be perceived as a standard since factors like the types of underlayer, thickness, deposition conditions, etc, could lead to deviation from this value [15]. For application purposes, the K u should fall under the negative range (5% to 30% from figure 1(b)) in order to keep the magnetization in-plane.…”

“…Efforts are overwhelmingly targeted at enhancing the K u of CoIr [15,16] which is good for stabilizing the directionality of magnetization. However, from an application viewpoint, other properties shouldlikewise not be ignored or compromised.…”

B2O3: Grain boundary material for high-Ku CoPt–oxide granular media with low degree of intergranular exchange coupling

“…2 , WO 2 , SiO 2 , Mn 3 O 4 , WO 3 , Co 3 O 4 , MoO 3 , and B 2 O 3 , which are recognized as hcp (10.0) and (11.0) for the CoPt grains of the granular layer, respectively, can be clearly observed. On the other hand, for the granular media with ZrO 2 , Cr 2 O 3 , Y 2 O 3 , and Al 2 O 3 , no clear hcp (10.0) diffraction can be observed, which means that the fcc atomic layer stacking in the hcp host atomic layer stacking is enhanced 20). Furthermore, diffractions at 2θ χ of around 38 and 69°for the Ru underlayer can be observed for all granular media.…”

Effect of additional elements on compositional modulated atomic layered structure of hexagonal Co80Pt20 alloy films with superlattice diffraction

“…This indicates that a small amount addition of Si more than 0.5 at.% into CoPt alloy will increase the fcc atomic layer stacking in the hcp host atomic layer stacking drastically. 14 In the out-of-plane profiles, for all CoPtSi alloy films, a diffraction of the CoPt film at diffraction angle (2θ) of 43.3 o can be observed. This diffraction is identified as hcp (00.2) which corresponds to the fundamental diffraction.…”