Magnetic properties and structural orderedness of CoxAl1-x Alloy films

The magnetic properties and the local atomic structures of ordered and disordered CoxAl1-x alloy films were investigated by using VSM and Co K-edge X-ray absorption spectroscopy measurements, respectively. From the VSM result, the saturation magnetization is enhanced and ΔHc (= right Hc - left Hc) is decreased when orderedness weakens and Co content increases. From the analysis of Co K-edge absorption spectra, the Co atoms in disordered films and Co-rich alloy films predominantly occupy Al-type sites, in contrast to ordered and equiatomic CoAl alloy films. Therefore, the probability of anti-structure Co and/or cluster formation increases as the disorderliness is enhanced and the Co concentration increases. Finally, we found that weakened orderedness and/or an increase in Co content in β-phase Co-Al alloy films led to the enhancement of the magnetization and reduction of ΔHc; due to the formation of Co clusters.