A paper led by our alumnus Dr. Mori on the magnetism and thermal expansion of iron hydride has been published in The Journal of Chemical Physics.
Under high pressure, iron can incorporate hydrogen into its crystal structure, which alters its physical properties such as magnetism and elasticity. In this study, we investigated the relationships among temperature, pressure, and magnetism in iron hydride (dhcp-FeH) synthesized under high-pressure and high-temperature conditions. Our in situ X-ray diffraction experiments and first-principles calculations reveal anomalous thermal expansion at the Curie temperature, i.e., the transition temperature from a ferromagnetic to a paramagnetic state. We also show that with increasing pressure, the Curie temperature is lowered while strengthening the coupling between magnetism and volume change, known as magnetoelastic coupling. This study provides unique experimental evidence of magnetically induced volume anomalies in a transition-metal hydride.
Mori Y., Aoki K., Kagi H., Takano M., Park I., Wang Z., Kim D., Tsujino N., Kakizawa S., and Higo Y. (2026) Pressure-induced thermal expansion anomalies in dhcp iron hydride associated with magnetoelastic coupling. The Journal of Chemical Physics, 165, 014705