Pressure-induced collapse of ferromagnetism in cobalt up to 120 GPa as seen via x-ray magnetic circular dichroism

The magnetism and structure of compressed Co has been studied up to 120 GPa using K-edge x-ray magnetic circular dichroism (XMCD) and x-ray absorption near edge spectroscopy (XANES). The XMCD signal decreases linearly with pressure and is totally suppressed around 120 GPa at ambient temperature. We detect local fcc-like atomic configurations starting from 80 GPa and at 120 GPa these represent at least 40% of the total. Supporting theoretical calculations indicate that the mixed hcp/fcc phase above 120 GPa is nonmagnetic. Comparison between the pressure evolution of magnetism and structure highlights major differences between the Fe and Co cases.