The oxypnictides ${\mathrm{Nd}}_{1-x}{\mathrm{Sr}}_x\mathrm{MnAsO}$ 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 ${\left[\mathrm{MnAs}\right]}^{-}$ layers are hole doped and the materials are driven metallic for $x\ge$ 0.05. A sizable positive magnetoresistance is observed at low temperature which demonstrates that multiple MR mechanisms are possible in LnMnAsO oxypnictides.

• Received 25 September 2013
• Revised 20 November 2014

DOI:https://doi.org/10.1103/PhysRevB.90.224413