Evidence for microstructural inhomogeneity in sputtered Co-Cr thin films

Abstract

Thin films of the perpendicular recording material CO IOOx Cr x (x = 17-23) were ion beam sputtered from alloy targets. The saturation magnetization and uniaxial anisotropy constant, as a function of temperature, both show a strong dependence on the substrate temperature during deposition Ts, indicating composition shifts which increase with Ts. The films have a columnar structure on a scale which does not depend on Ts in contrast to the grain size. From studies of the phase relations in bulk Co-Cr alloys and diffusion couples it is concluded that phase separation of ordered Co-Cr phases does not occur at high Ts. Instead the composition shifts and the grain refinement at higher Ts are proposed to be caused by oxygen gettering and oxide trapping during film growth.

Bit patterned media optimization at 1 Tdot/in2 by post-annealing

“…The additional post-annealing step then thermally activates a Cr diffusion process from the core to the periphery of the islands. This mechanism as first suggested by Smits et al 18 is additionally enhanced by the increased oxygen-reactivity of Cr over Co, which triggers oxygen transfer from the Co atoms to the Cr atoms, as those reach the periphery of the islands. As a result the Cr diffusion process towards the island edges followed by the oxygen transfer from the Co to the Cr within the island edge region finally yields an island structure with a CoPt rich high anisotropy/high moment island core and a protective nonmagnetic Cr/Cr-oxide rich island shell [19][20][21] as illustrated in Fig.…”

Magnetic microstructures in Co-Cr sputtered thin films for perpendicular recording

“…There are many different possible explanations of such a CS structure (which has never been observed in Co-Cr bulk alloys) in the literature. [30][31][32][33][34][35][36][37][38]. Most consistent wor~ in this field has been published by [39][40][41][42][43].…”

Magnetic structures in CoCr media for perpendicular magnetic recording

“…The spatial periodicity of CS in sputtered Co-Cr layers on top of soft magnetic Ni-Fe layers is in the range of 3-7 nm [13]. The are many different possible explanations of such a CS structure (which has never been observed in Co-Cr bulk alloys) in the literature [14][15][16][17][18][19][20][21][22]. Most consistent work in this field has been published in Refs.…”