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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 (TN = 359(2) K). At room temperature the magnetic propagation vector k = 0 and the Mn moments are directed along the crystallographic c-axis (mMn = 2.41(6) BM). Upon cooling a spin reorientation (SR) transition of the Mn moments into the ab-plane occurs (TSR = 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 mab,Mn = 3.72(1) BM and mab,Nd = 1.94(1) BM. The electrical resistivity is characterized by a broad maximum at 250 K, below which it has a metallic temperature dependence but semiconducting magnitude (rho250K = 50 Ohm cm, residual resistivity ratio = 2), and a slight upturn at the SR transition.