Negative Thermal Expansion and Spontaneous Magnetostriction of Nd_2Fe_16.5Cr_0.5 Compound

The structural, thermal expansion, and magnetic properties of the Nd_2Fe_16.5Cr_0.5 compound are investigated by means of x-ray diffraction and magnetization measurements. The Nd_2Fe_16.5Cr_0.5 compound has a rhombohedral Th_2Zn_17-type structure. There exists a small negative thermal expansion resulting from a spontaneous magnetostriction in the magnetic state of the Nd_2Fe_16.5Cr_0.5 compound. The average thermal expansion coefficient is -1.06\times 10^-6/K in a temperature range 299–394 K. The spontaneous magnetostrictive deformation and the Curie temperature are discussed.