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A systematic study of the temperature and magnetic field dependence of the longitudinal and transverse resistivities of epitaxial thin films of magnetite (Fe 3 O 4 ) is reported. The anisotropic magnetoresistance (AMR) and the planar Hall effect (PHE) are sensitive to the in-plane orientation of current and magnetization with respect to crystal axes in a way consistent with the cubic symmetry of the system. We also show that the AMR exhibit sign reversal as a function of temperature, and that it shows significant field dependence without saturation up to 9 T. Our results provide a unified description of the anisotropic magnetoresistance effects in epitaxial magnetite films and illustrate the need for a full determination of the resistivity tensor in crystalline systems.

We measured the anisotropic magnetoresistance (AMR) and the planar Hall effect (PHE) in a [001] oriented epitaxial thin film of La0.7Ca0.3MnO3 (LCMO) as a function of magnetic field, temperature, and current direction relative to the crystal axes. We find that both AMR and PHE in LCMO depend strongly on the current orientation relative to the crystal axes, and we demonstrate the applicability of AMR and PHE equations based on a fourth order magnetoresistance tensor consistent with the film symmetry.

We present planar Hall effect measurements of elliptical permalloy sensors having different aspect ratios and thicknesses along with extensive numerical simulations and analytical analysis. We identify an upper limit for the sensor minor axis on the order of 1 μm above which hysteresis effects intensify. We also find that the increased ratio between the ellipse axes and thickness enhances the magnetic response of the sensor.

We study the anisotropic magnetoresistance and planar Hall effect of La0.8Sr0.2MnO3 when the field is rotated out of the film plane. We fit the data with a model, which consists of two independent contributions related to (a) the orientation of the magnetization relative to the crystal axes and (b) the orientation of the magnetization relative to the current. We find that the first contribution exhibits a two-fold symmetry, which cannot be explained by the angular dependence of the magnetization magnitude, suggesting an intrinsic source which reflects a deviation from cubic symmetry.