Structure and magnetism in compressed iron–cobalt alloys

Combined Co K-edge XANES-XMCD and XRD measurements were used to shed light on the magnetic and structural phase diagram of the Fe1−x Co x alloy under HP in the Co-rich region (x≥0.5). At 0.5≤x≤0.75, the alloy shows a pressure-induced structural/magnetic phase transition from bcc-FM to hcp-non-FM phase just like pure iron but at higher pressures. The x=0.9 sample has an fcc structure in the pressure range investigated but presents an FM to non-FM transition at P=64 GPa, a significantly lower pressure compared with pure Co (predicted ≈120 GPa), showing that Fe impurities strongly affect the HP Co response.