A high pressure neutron study of colossal magnetoresistant NdMnAsO0.95F0.05

A high pressure neutron diffraction study of the oxypnictide NdMnAsO0.95F0.05 has been performed at temperatures of 290-383K and pressures up to 8.59 GPa. The results demonstrate that the antiferromagnetic order of the Mn spins is robust to pressures of up to 8.59 GPa. T-N is enhanced from 360 to 383K upon applying an external pressure of 4.97 GPa, a rate of 4.63KGPa(-1). NdMnAsO0.95F0.05 is shown to violate Bloch's rule which would suggest that NdMnAsO0.95F0.05 is on the verge of a localized to itinerant transition. There is no evidence of a structural transition but applied pressure tends to result in more regular As-Mn-As and Nd-O-Nd tetrahedra. The unit cell is significantly more compressible along the c-axis than the a-axis, as the interlayer coupling is weaker than the intrinsic bonds contained within NdO and MnAs slabs.