Evolution of microstructure and magnetic properties in magnetron-sputtered CoCr thin films

Abstract

The microstructure and magnetic-structure development in magnetron-sputtered Co-22at%Cr thin films deposited on amorphous substrates has been examined systematically and in detail. It has been found that the initial deposit is amorphous up to a thickness of ~ 5 nm. By 10 nm thickness, a polycrystalline highly hcp c-axis textured (out of the film plane) microstructure is observed. At 50 nm thickness, a distinct columnar morphology has developed. A distinct subgrain structure was also observed in the thinner films (10-50 nm). The magnetization is initially in-plane and retains in-plane components up to a thickness of ~ 50 nm, after which it is predominantly out-of-plane. The effects of in-plane film stress are reflected in the effective anisotropy field and are most evident in the thinner films, where the stress is highest. The thinnest (10 nm) films display in-plane 180 ° domain walls while thicker (50 nm) films exhibit out-of-plane "dot"-type domain structures. The "dot" domains were observed even in films that had not yet developed a columnar morphology. Intermediate-thickness films show a "feather-like" contrast, indicating that both in-and out-of-plane magnetization components are present. Intrinsic film stress was found to play a major role in determining the preferred magnetization direction and, thus, the resulting magnetic domain configurations.

Exchange biasing and coercivity enhancement in CoCr/FeMn bilayers with granular ferromagnet

“…It has already been verified by our initial transmission electron microscopy observation, which will be published elsewhere. For the as-prepared thin films, it was generally accepted that the c axis of the hcp Corich component is aligned in the film plane randomly [13]. Therefore, the isotropic in-plane hysteresis loops in Fig.…”

Coercivity and magnetization reversal mechanism in ferromagnet/antiferromagnet bilayers: Correlation with microstructure of ferromagnetic layers

“…1͒, the CoCr layer consists of Co-rich and Cr-rich phases and the former grains are separated by the latter ones. For small CoCr layer thickness, the c axis of the hcp Co-rich component is distributed in the film plane randomly, 16 which results in isotropic in-plane hysteresis loops in Fig. 3.…”

“…Small grains and even amorphous structure were observed in as-prepared thin CoCr layer films. 16 Secondly, it is caused by the inhomogeneous distribution of the composition in CoCr layers. This is because the position of the diffraction peak is strongly related to the composition.…”

Influence of the Cr and Ni concentration in CoCr and CoNi alloys on the structural and magnetic properties

“…Only few studies report on Co-Cr films synthesis with a thickness exceeding 1 mm. Among them, as in the case of CoNi, H c has been studied as a function of various parameters like film thickness [22], temperature [23,24] and stress [25]. But in addition, more attention was paid to characterize the intrinsic parameters of the CoCr layers beyond Hc.…”