J. M. S. Skakle | Searcharxiv

arXiv2012

Colossal Magnetoresistance in the Mn2+ Oxypnictides NdMnAsO1-xFx

Colossal magnetoresistance (CMR) is a rare phenomenon in which the electronic resistivity of a material can be decreased by orders of magnitude upon application of a magnetic field. Such an effect could be the basis of the next generation of magnetic memory devices. Here we report CMR in the antiferromagnetic oxypnictide NdMnAsO1-xFx as a result of competition between an antiferromagnetic insulating phase with strong electron correlations and a paramagnetic semiconductor upon application of a magnetic field. The discovery of CMR in antiferromagnetic Mn2+ oxypnictide materials could open up an array of materials for further investigation and optimisation for technological applications.

cond-mat.str-el↗

arXiv2012

A variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LnMnAsO (Ln = La, Nd)

A variable temperature neutron and synchrotron diffraction study have been performed on the giant magnetoresistant oxypnictides LnMnAsO (Ln = La, Nd). The low temperature magnetic structures have been studied and results show a spin reorientation of the Mn2+ spins below TN (Nd) for NdMnAsO. The Mn2+ spins rotate from alignment along c to alignment into the basal plane and the Mn2+ and Nd3+ moments refine to 3.54(4) μB and 1.93(4) μB respectively at 2 K. In contrast there is no change in magnetic structure with temperature for LaMnAsO. There is no evidence of a structural transition down to 2 K, however discontinuities in the cell volume, Ln-O and Mn-As bond lengths are detected at \sim 150 K for both materials. This temperature coincides with the electronic transition previously reported and suggests a coupling between electronic and lattice degrees of freedom.

cond-mat.str-el↗