Eur. Phys. J. B 41, 517-524 (2004)
https://doi.org/10.1140/epjb/e2004-00345-0

Amorphous to polycrystalline transition in Co_xSi_1-x alloy thin films

¹ Dpto. Física, Universidad de Oviedo, Av. Calvo Sotelo s/n, 33007 Oviedo, Spain
² IPCMS-GEMM (CNRS-UMR 7504) 23 Rue de Loess, 67037 Strasbourg Cedex, France

Corresponding author: ^a mvelez@condmat.uniovi.es

Received: 7 April 2004
Revised: 26 July 2004
Published online: 5 November 2004

Abstract

The transition from amorphous to polycrystalline microstructure has been studied in sputtered Co_xSi alloy films by structural, magneto-optical and Nuclear Magnetic Resonance measurements. For , Si is diluted into Co without significantly altering the polycrystalline microstructure, composed of a mixture of hcp and fcc grains. However, the fraction of Co atoms that contribute to the Nuclear Magnetic Resonance signal is found to decrease steeply (down to about 60% at x = 0.76) suggesting a microscopic segregation of a Si rich phase that induces a large degree of disorder. This is reflected in a harder magnetic behavior and a strong anisotropy dispersion. Below x = 0.75, the transition to an amorphous microstructure results in a sudden increase in the fraction of Co atoms within a ferromagnetic phase, indicating the recovery of the microscopic homogeneity. Also a significant enhancement of the macroscopic magnetic anisotropy is found for amorphous films with compositions right below the transition. Within the amorphous phase a second regime of Si segregation appears characterized by a constant Co local environment and constant magnetic properties. Finally, for x=0.65 there is a significant Si enrichment in the Co environment and the films become non magnetic for compositions below this point.