${}^{139}\mathrm{La}$ NMR evidence for sensitivity of local structure to magnetic field in ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_3$

We report ${}^{139}\mathrm{La}$ nuclear-magnetic-resonance measurements on ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_3.$ Two resonance peaks observed in zero applied field are identified as ferromagnetic (FM) resonances arising from FM domains with eight nearest Mn moments almost fully polarized. The two La sites are distinguished by experiencing different covalent configurations with respect to the nearest Mn ions, likely caused by the charge/orbital ordering. The two sites collapse into one in the presence of a strong magnetic field, indicating the close relationship between magnetism and the lattice deformation.