Characterization of CoCrTa Alloy Thin Films by X-Ray Powder Diffraction

Abstract

Crystalline structures of one single- and two multi-layer magnetic CoCrTa films were characterized by X-ray powder diffraction technique. Structural parameters such as crystalline phase, preferred orientation, crystallite size and microstrain (which control the magnetic properties) have been determined. Polycrystalline diffractions from lattice planes parallel and perpendicular to the surface of a film were obtained with the specimen in reflection and in transmission, respectively. Phase identification of the ternary alloy (Co85Cr15)90Ta10 magnetic layers of the specimens indicated a disordered solid solution of Cr and Ta in Co, and the alloy has a hexagonal close-packed (h.c.p.) (A3) structure. Line broadening analysis showed crystallite size anisotropy and columnar CoCrTa grains. The crystal growth was disrupted by the nonmagnetic “amorphous” spacing layers in the multi-layer specimens. The disruption increased with the decreasing magnetic layer thickness. Compared to those of the single-layer film, a lesser (OOℓ) basal plane preferred orientation with a larger perpendicular c-axis dispersion, smaller crystallite sizes and higher microstrains at L⩾50Å were obtained in the multi-layer specimen consisting of eight 500Å thick magnetic layers. The magnetic particles were found to be poorly crystallized in the multi-layer specimen where the thicknesses of the 33 magnetic layers were limited to 150Å each. © 1987, Cambridge University Press. All rights reserved.