From antiferromagnetic insulator to ferromagnetic metal; Effect of hydrogen substitution in LaMnAsO

Hanna, Taku*; Matsuishi, Satoru*; Kodama, Katsuaki   ; Otomo, Toshiya*; Shamoto, Shinichi  ; Hosono, Hideo*

Manganese oxyarsenide hydrides LaMnAsOH ( = 0-0.73) were synthesized by a solid state reaction under a high pressure of 2 GPa. The hydride ions H in O sites induced an insulator-to-metal conversion and suppressed the antiferromagnetic ordering of Mn spins. Instead, ferromagnetism with negative magnetoresistance was observed. The Curie temperature and saturated moment per Mn increased with up to 264 K and 1.5 , respectively, at = 0.73. These results indicate that H donate conduction electrons to the MnAs layer, mediating a direct ferromagnetic interaction between Mn atoms.