Influence of 3d-Metal Doping on Magnetotransport Properties of Magnetite Thin Films

In this paper, variation in magnetoresistance (MR) by transition-metal (TM) doping in magnetite (Fe
₃
O
₄
) has been investigated. The samples (T
_x
Fe
_3-x
O
₄
, T = V, and Cr) were polycrystalline and prepared as thin films by a sol-gel method. As the TM composition (x) increases, the MR strength is reduced but the reduction rate with x differs significantly for the two TM-doping cases. For the V-substituted samples, the MR is reduced rapidly with x and no significant MR is detected above x = 0.11. On the other hand, the Cr-substituted samples exhibit the MR effect up to x = 0.49. Such difference in MR strength between the two TM-doping cases is attributable to the difference in the intrinsic properties of the ternary ferrites such as electronic structure and carrier spin polarization.