Fe-spin reorientation in PrFeAsO: Evidences from resistivity and specific heat studies

We report the magnetic field dependence of resistivity () and specific heat (C) for the non-superconducting PrFeAsO compound. Our study shows a hitherto unobserved anomaly at T SR in the resistivity and specific heat data, which arises as a result of the interplay of antiferromagnetic (AFM) Pr and Fe sublattices. Below the AFM transition temperature (T N Pr), Pr moment orders along the crystallographic c axis and its effect on the iron subsystem causes a reorientation of the ordered in-plane Fe moments in a direction out of the ab plane. Application of magnetic field introduces disorder in the AFM Pr sublattice, which, in turn, reduces the out-of-plane Pr-Fe exchange interaction responsible for Fe spin reorientation. Both in (T) and d (C / T) / dT curves, the peak at T SR broadens with the increase of H due to the introduction of the disorder in the AFM Pr sublattice by magnetic field. In the (T) curve, the peak shifts toward lower temperature with H and disappears above 6 T, while in the d (C / T) / dT curve, the peak remains visible up to 14 T. The broadening of the anomaly at T N Pr in C (T) with increasing H further confirms that magnetic field induces disorder in the AFM Pr sublattice.