Ferromagnetic shape memory effects in tetragonally distorted antiperovskite manganese nitrides

Tetragonally distorted antiperovskite Mn3CuN1-delta exhibits huge magnetostriction of up to 2000 ppm, which is reasonably ascribed to ferromagnetic shape memory effects. The uniqueness of Mn3CuN1-delta as a ferromagnetic shape memory alloy is exemplified by its nitrogen deficiency. The easy axis for magnetization rotates from the longer a axis in Mn3CuN0.97 to the shorter c axis in Mn3CuN0.78. The operating magnetic field for magnetostriction is much lower for Mn3CuN0.28 than for Mn3CuN0.92, suggesting supermagnetostriction. These characteristic behaviors can be explained consistently in terms of low magnetocrystalline anisotropy, which is a striking difference from other ferromagnetic shape memory alloys such as Heusler Ni2MnGa. (C) 2011 Elsevier B.V. All rights reserved.