The crystallographic texture of Cr film deposited on glass substrates is found to depend on the film thickness d cr and the substrate temperature T,. Without substrate preheating, only the Cr {IIO} peak was observed in the x-ray diffraction spectra for films between 60 and 400 11m in thickness. With increasing T, (by substrate preheating), the Cr{200} peak became observable at progressively increasing intensity, whereas the intensity of the {11O} peak decreased.Consequently the nO-nm-thick films deposited at T,. >200 °C are predominantly {100} textured. However, even for these high T, values (>200 °C), the {11O} peak intensity increases with increasing film thickness. Larger film thickness values are required at higher T, for the {11O} texture to overcome the {IOO} texture. The grain size of the Cr films deposited on glass increases with film thickness and with substrate temperature.4913
Various CO-based alloys (hcp) have been developed for use as longitudinal magnetic recording media. Many investigators have found that the use of Cr underlayers (bcc) greatly affects the magnetic properties of the films. Several investigators have related this to the effect of the Cr underlayer on the crystallographic texture of the thin magnetic CO-based films. In this review paper some of the evidence for the effect of Cr orientation on the crystallographic orientation of CO-based thin films is presented. This evidence is based on x-ray diffraction, selected area electron diffraction, electron micro-diffraction of the Co/Cr bi-layer film and atomic resolution electron microscopy of cross sections of the bi-lay9 films. We show that a (110) Cr surface gives rise to a (1011) type CO-based alloy thin film texture, whereas a (200) Cr surface produces a ( 1120) type CO-based alloy thin fiim texture.It has been nearly a quarter of a century since the discovery that a Cr underlayer increases the in-plane magnetic coercivity of sputtered CO based alloy thin films [1,2]. One of the proposed mechanisms for this increase in coercivity is the supposition that the Cr underlayer produces a CO film with a preferred crystallographic orientation [3,4]. In a previous paper we reviewed some of the evidence for crystallographic texture in these thin films [5]. In this paper we review four experimental techniques that can be used to investigate the orientation relationships (OR) between the magnetic Cobased film and the Cr underlayer. These techniques are x-ray diffraction, selected area (electron) diffraction (SAD), electron microdiffraction (ID) and atomic resolution electron microscopy. Figure 1 is a schematic drawing showing the important components of a thin film disk for magnetic recording. Of interest to us in this review is the crystallographic orientation relationships between the grains in the magnetic film and those in the Cr (bcc) underlayer. The magnetic films which we discuss will all be alloys of CO, usually with the hcp structure. Hence, the ORs of interest to us are those between hcp and bcc. Since certain interplanar spacings in CO and Cr have nearly the same values, a special set of ORs are established during the deposition process of the CO-based alloy onto the Cr underlayer. The govemment has certain rights in this material. I NiP (amorphous) 10 p I Figure 1. A schematic drawing of the various layer in a hard disk We start with a brief review of the important planes in the bcc and hcp structures. Figure 2(a) shows the two types of planes of Cr which are most likely to be parallel to the thin film surface, namely the (200) and (110) planes. The (110) planes are the closest-packed planes for the bcc structure, and in the case of Cr films are the ones which are most likely to lie parallel to the film surface when the films are grown without substrate heating [6]. When deposited at elevated temperatures (>15OoC) the (200) texture is commonly observed [7-lo]. The figures shown in 2(b) highlight the hexagonal close pa...
Various crystallographic textures of Co-alloy/Cr bilayer thin films are discussed based on microdiffraction and selected-area diffraction (SAD) results. In order to understand the origin of the crystallographic texture of the Co thin films, the orientation relationships between the Co and Cr grains were determined by the electron microdiffraction technique. From this information, we suggest that the {110} Cr underlayer texture may not necessarily be required to obtain the highest in-plane coercivity in Co films. In order to evaluate the crystallographic texture of the film by SAD patterns, normalized intensity of SAD patterns for various thin-film textures have been calculated. Using these calculations, we interpret the SAD patterns taken from various Co and Cr thin films.
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