AI Article Synopsis
- A new mechanism of colossal magnetoresistance (CMR) was reported in electron doped manganese oxypnictides, showing remarkable -95% magnetoresistance at 3 K.
- Replacement of Nd with Pr in the material leads to significant changes, as CMR disappears, and instead a negative magnetoresistance of -13.4% is observed in PrMnAsO0.95F0.05 below 35 K.
- A structural transition at 35 K from tetragonal to orthorhombic symmetry, influenced by Pr 4f electrons, is identified, suggesting the negative magnetoresistance is linked to reduced magnetic scattering when a magnetic field is applied.
Article Abstract
We have recently reported a new mechanism of colossal magnetoresistance (CMR) in electron doped manganese oxypnictides NdMnAsO1-xFx. Magnetoresistances of up to -95% at 3 K have been observed. Here we show that upon replacing Nd for Pr, the CMR is surprisingly no longer present. Instead a sizable negative magnetoresistance is observed for PrMnAsO0.95F0.05 below 35 K (MR7T (12 K) = -13.4% for PrMnAsO0.95F0.05). A detailed neutron and synchrotron X-ray diffraction study of PrMnAsO0.95F0.05 has been performed, which shows that a structural transition, Ts, occurs at 35 K from tetragonal P4/nmm to orthorhombic Pmmn symmetry. The structural transition is driven by the Pr 4f electrons degrees of freedom. The sizable -MR observed below the transition most likely arises due to a reduction in magnetic and/or multipolar scattering upon application of a magnetic field.
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