Influence of anisotropic strain relaxation on the magnetoresistance properties of epitaxial Fe₃O₄ (110) films

We studied Fe₃O₄ (110) films grown epitaxially on MgO (110) substrates using oxygen plasma assisted molecular beam epitaxy. The films with thickness of 30-200 nm showed anisotropic in-plane partial strain relaxation. Magneto resistance (MR) measurements with current and magnetic field along 〈001〉 direction showed higher MR compared to 〈1¯10〉 direction. Maximum value of MR was measured at Verwey transition temperature for both directions. We explain the observed anisotropy in the MR on the basis of the effects of anisotropic misfit strain, and the difference between the density of antiferromagnetically coupled antiphase boundaries formed along 〈001〉 and 〈1¯10〉 crystallographic directions, suggesting the dependence of spin polarisation on the anisotropic strain relaxation along the said crystallographic directions.