Effects of Sputtering Conditions on Texture, Microstructure and Magnetic Properties of the CoCrPt/NiAl Thin Films
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ABSTRACT The effects of sputtering argon pressures and sputtering power on the microstructure, texture and magnetic properties of NiAI underlayers on CoCrPt films were investigated. In this paper, the relationship between the sputtering conditions, microstructure, crystallographic texture and magnetic properties of these thin films will be discussed. By controlling the sputtering pressure and sputtering power, the texture and microstructure of NiAI underlayers were found to vary. This in turn was found to influence the magnetic properties of CoCrPt thin films. It was found that 10 mtorr is the optimum pressure to deposit the NiAl thin films to obtain the best magnetic properties for our system. At this argon pressure, the coercivity reached a maximum value because of the strongest CoCrPt (10 1-0) texture and smallest grain size. At lower argon pressures (< 10 mtorr), NiAI tended to have a (110) texture reducing the CoCrPt (10 10) texture, which in turn reduced the CoCrPt coercivity and S*. Also, high NiAl deposition pressures (>30 mtorr) yielded larger grains and a weaker CoCrPt (10 10) texture, thereby decreasing the coercivity of the CoCrPt films. Increasing the sputtering power has been found to increase the CoCrPt coercivity and S* value. However, the grain sizes of the CoCrPt/NiAl thin films deposited at higher sputtering power were larger than those obtained at lower sputtering power. INTRODUCTION To achieve high density longitudinal recording, hcp Co-based thin films with their c-axis lying in the plane of the film are needed as well as small and magnetically isolated grains[ 1-5]. Compared to the traditional Cr underlayer, the new B2 underlayer was found to possess not only the unique (112) texture but also very small grains (15 nm) [6,7]. The B2 (112) texture can induce the CoCrPt (10 TO) texture with the c-axis to lie in the plane of the thin film. This unicrystalline CoCrPt caused by the (10 T0) texture is believed to have higher coercivity than the bicrystal resulting from the CoCrPt (1120) texture. At the same time, the smaller grain size of the B2 underlayer can effectively reduce the media noise. Also, these textures and microstructural features, that strongly affect the magnetic properties, can be further improved by changes in the deposition process. In this paper, we will focus on the effects of the deposition conditions on one of the B2 underlayer samples, NiAl underlayers. The emphasises of this research are to investigate (1) the effects of the argon pressure and sputtering power of the NiAl underlayers on the crystallography texture and microstructure (2) the correlation of the magnetic properties of the CoCrPt films with the crystallographic texture and microstructure (3) optimization of the magnetic properties by controlling the argon pressure and sputtering power of the NiAl underlayers. 199 Mat. Res. Soc. Symp. Proc. Vol. 517 01998 Materials Research Society
EXPERIMENT The CoCrPt / NiAl thin films were deposited on glass substrates by RF diode sputtering in an LH Z-400 system. The base p
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