Interface effects on magnetoresistance and magnetic-field-reduced Raman scattering in magnetite

Our work demonstrates that magnetoresistance of the polycrystalline magnetite decreases with the reduction in average grain size, suggesting that the spin-dependent transporting phenomenon is associated with the interface microstructure. Also, the reducing peak intensity of the Raman spectra near 660 cm^-1 was observed while its full width at half-maximum remains invariable, as applied a field. It demonstrates that the phonon mode becomes softening upon applying a field. A possible physical explanation is proposed that magnetic field-induced the enhanced electron-electron correlation. This is consistent with the previous results about magnetite.