Nd-induced Mn spin-reorientation transition in NdMnAsO

A combination of synchrotron x-ray, neutron powder-diffraction, magnetization, heat-capacity, and electrical-resistivity measurements reveals that NdMnAsO is an antiferromagnetic semiconductor with large Neel temperature [T_N =359 (2) K]. At room temperature the magnetic propagation vector k=0 and the Mn moments are directed along the crystallographic c axis [m _Mn =2.41 (6) µ_B]. Upon cooling a spin-reorientation (SR) transition of the Mn moments into the ab plane occurs (T_SR =23 K). This coincides with the long-range ordering of the Nd moments, which are restricted to the basal plane. The magnetic propagation vector remains k=0. At base temperature (1.6 K) the fitted moments are m_ab,Mn =3.72 (1) µ_B and m_ab,Nd =1.94 (1) µ_B. The electrical resistivity is characterized by a broad maximum at 250 K, below which it has a metallic temperature dependence but semiconducting magnitude (?_{250 K} =50 Ocm, residual resistivity ratio=2), and a slight upturn at the SR transition. © 2010 The American Physical Society.