Magnetoresistance of magnetite

Abstract

The resistivity and magnetoresistance of a magnetite single crystal and Fe3 O4 films of various thicknesses were measured in the temperature range 70 K<T <300 K and in magnetic fields in the range -1 T µ0 H 1 T. The magnetoresistance depends on both current and magnetic field direction. The anisotropic magnetoresistance is determined as the difference of the magnetoresistances in longitudinal and transverse geometry. The data were analysed within a phenomenological model above the Verwey temperature. The anisotropic magnetoresistance for currents along [100] was found to show a sign change simultaneously with that of the crystalline anisotropy constant K 1 . Whereas the magnetoresistance of the single crystal saturates above the anisotropy field, the Fe3 O4 films show a significant high-field magnetoresistance depending linearly on the applied field. This behaviour was attributed to carrier transport across antiphase boundaries. A simple model was proposed that is in good qualitative agreement with the data. The single crystal shows a significant decrease of the Verwey transition in magnetic fields applied along [110]; this leads to a magnetoresistance of 70% in an external field of 1 T.

The magnetic and magnetoresistance properties of ultrathin magnetite films grown on MgO substrate

“…MR of magnetite film is related to electron transfer across the APBs. 13 When a magnetic field is applied, the magnetization of domains separated by the APBs turns towards the external field direction and angles between adjacent spins ͑ ͒ decrease, thus, the electrons undertake less scattering between domains. This is the origin of negative MR in magnetite.…”

Epitaxial growth and ferrimagnetic behavior of MnFe2O4(111) ultrathin layers for room-temperature spin filtering

“…APBs are stacking defects of the atomic planes in the spinel lattice corresponding to a half-lattice translation of the cationic sublattice, whereas the oxygen sublattice remains unchanged. In the case of Fe 3 O 4 , these APBs have been widely studied due to their important effect on the magnetic 17,27 and magnetotransport [28][29][30] properties of this material. In the case of MnFe 2 O 4 , much less is known.…”

Origin of the giant magnetic moment in epitaxialFe3O4thin films

“…2͒ and its characteristic metal-insulator transition at 120 K ͑Verwey transition͒. [3][4][5] Differences between some properties of bulk magnetite and epitaxial thin films have been observed, such as an increased resistivity with decreasing film thickness, [6][7][8] negative magnetoresistance, [9][10][11] decreased and broadened Verwey transition temperature ͑T V ͒, 7,12,13 superparamagnetism in ultrathin films, 14,15 decreased saturation magnetization, [16][17][18][19] and anomalous, planar, and ordinary Hall effects. [20][21][22] This anomalous behavior has often been associated to the film microstructure and the presence of structural growth defects called antiphase boundaries ͑APBs͒.…”