Exchange bias up to room temperature in antiferromagnetic hexagonal Mn 3 Ge

Mn 3.04 Ge 0.96 has a hexagonal crystal structure, which can be stabilized by high-temperature annealing, and shows antiferromagnetic order with a small ferromagnetic component of less than 0.1 μ B and a coercivity of 0.45 T. In the ordered phase, magnetization curves M ( H ) exhibit an exchange bias of 62 mT at T = 2 K after field cooling, which is observable up to room temperature. The exchange anisotropy is suggested to originate from the exchange interaction between the host of triangular-antiferromagnetic Mn 3 Ge units and embedded ferrimagnetic-like clusters. Such clusters develop when excess Mn atoms occupy empty Ge sites in the original triangular-antiferromagnetic structure of Mn 3 Ge.