Exchange anisotropy in 'amorphous' Co-Gd films. II

Abstract

For pt.I see J. Appl. Phys., vol.64, p.5431 (1988). The authors report the results of magnetization, transmission-electron-microscopy (TEM), and X-ray-diffraction studies of GdCo/sub x/ films sputtered onto Si or sapphire substrates at approximately 90 degrees C ambient temperature. The composition range studied was x=2-8.5. Over the composition range defined approximately by 5>x>3, the films, which are 1-3- mu m thick, exhibit a unidirectionally displaced B-H loop characteristic of an exchange-coupled phase. TEM studies indicated that the samples with the shifted loops consist of a mixture of amorphous and microcrystalline phases. The characteristic size of the microstructure is 10-20 AA. Electron diffraction shows a very broad ring characteristic of the amorphous phase together with six or seven sharper rings characteristic of crystalline material, which correlate best with the hexagonal GdCo/sub 5/ structure or to a high-temperature hexagonal Gd/sub 2/Co/sub 17/ phase. The diffraction pattern remains virtually unchanged over the composition range x=3-8, even though the phase diagram shows several line compounds. This leads to the conclusion that the microcrystalline material consists of one, or perhaps more than one, metastable phase over the indicated composition range. X-ray diffraction shows only one broad maximum. No crystalline peaks have yet been resolved. >