Short-range magnetic collapse of Fe under high pressure at high temperatures observed using x-ray emission spectroscopy

Understanding the high-pressure electronic properties of Fe still poses both theoretical and experimental challenges. Here, we evidence the short-range magnetic collapse of Fe in the gamma phase by x-ray emission spectroscopy carried out in situ under high-pressure and high-temperature conditions, up to 20 GPa and 1400 K. We find an abrupt decrease in the Fe spin state in gamma-Fe at high pressure similar in amplitude to the known alpha-epsilon magnetic collapse transition. A careful analysis of the Fe spin state in the epsilon phase indicates a sluggish diminution right above the transition pressure, bearing out recent predictions of residual, likely noncollinear, magnetism in this phase. In the gamma phase, our results demonstrate that the dominant mechanism at high pressure is a high-spin to low-spin transition. Implications for the elastic properties of Fe at extreme conditions are analyzed.