Electronic and magnetic properties of Nd1-xSrxMnAsO oxyarsenides

The oxypnictides Nd1-xSrx MnAsO have been successfully synthesized with x up to 0.1. A synchrotron x-ray diffraction study demonstrates that there is no change in crystal symmetry upon doping with Sr. An expansion of the interlayer distance between Nd-O-Nd and As-Mn-As blocks is observed with increasing x. Results from variable temperature neutron diffraction and resistivity measurements show that the local moment antiferromagnetic order of the Mn spins is preserved as the [MnAs]-layers are hole doped and the materials are driven metallic for x >= 0.05. A sizable positive magnetoresistance is observed at low temperature which demonstrates that multiple MR mechanisms are possible in LnMnAsO oxypnictides.