The structural and magnetic phase transitions have been studied on NdFeAsO single crystals by neutron and x-ray diffraction complemented by resistivity and specific heat measurements. Two low-temperature phase transitions have been observed in addition to the tetragonal-to-orthorhombic transition at T_S = 142 K and the onset of antiferromagnetic (AFM) Fe order below T_N = 137 K. The Fe moments order AFM in the well-known stripe-like structure in the (ab) plane, but change from AFM to ferromagnetic (FM) arrangement along the c direction below T* = 15 K accompanied by the onset of Nd AFM order below T_Nd = 6 K with this same AFM configuration. The iron magnetic order-order transition in NdFeAsO accentuates the Nd-Fe interaction and the delicate balance of c-axis exchange couplings that results in AFM in LaFeAsO and FM in CeFeAsO and PrFeAsO.
@article{arxiv.1006.1135,
title = {Interplay between Fe and Nd magnetism in NdFeAsO single crystals},
author = {W. Tian and W. Ratcliff and M. G. Kim and J. -Q. Yan and P. A. Kienzle and Q. Huang and B. Jensen and K. W. Dennis and R. W. McCallum and T. A. Lograsso and R. J. McQueeney and A. I. Goldman and J. W. Lynn and A. Kreyssig},
journal= {arXiv preprint arXiv:1006.1135},
year = {2010}
}
Comments
revised; 4 pages, 3 figures; accepted for publication in Phys. Rev. B