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

Our work demonstrates that magnetoresistance of the polycrystalline magneti te decreases with the reduction in average grain size, suggesting that the spin-dependent transporting phenomenon is associated with the interface mic rostructure. Also, the reducing peak intensity of the Raman spectra near 66 0 cm(-1) was observed while its full width at half-maximum remains invariab le, as applied a field. It demonstrates that the phonon mode becomes soften ing 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.