Large Magnetoresistance in Magnetite Pellets

The experimental evidence of a large magnetoresistance in magnetite pellets is provided in this paper. Applying a magnetic field along the length of the four-point resistivity probe, on the surface of a bulk magnetite pellet, results in large magnetoresistance change in the order of 150%. Measurements were realized in 10-3 mbar vacuum with excitation currents from 0.1 A up to 0.5 A, with magnetic field from 0 mT up to 250 mT. After the exponential decrease of resistance because of the increase of the carrier number due to the temperature elevation and the semiconducting nature of the magnetite pellets, the steady-state resistance of the sample was dependent on the externally applied field. The drop of resistivity is attributed to the parallelization of the magnetic flux B of the magnetite pellet with the excitation current, thus resulting in an increase of the corresponding mean free path.