Spin-glass behavior in the antiperovskite manganese nitride Mn3CuN codoped with Ge and Si

Antiperovskite manganese nitrides Mn3(Cu0.6SixGe0.4−x)N (x=0.05x=0.05, 0.1, 0.15) were prepared and their negative thermal expansion, magnetic and specific heat properties were investigated. A frozen state with a freezing temperature was found at ∼207 K in Mn3(Cu0.6Si0.15Ge0.25)N. This indicates that Mn3(Cu0.6Si0.15Ge0.25)N exhibits a spin glass state at low temperatures. We discussed the cause of spin glass behavior and correlated this spin glass behavior with broadening of the negative thermal expansion operation-temperature window of the manganese nitrides Mn3(Cu0.6Si0.15Ge0.25)N.