Anisotropic magnetoresistance and planar Hall effect in La2∕3Ca1∕3MnO3 thin films with misfit strain

Abstract

In our previous study anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) of epitaxial La2∕3Ca1∕3MnO3 (LCMO) thin films grown on SrTiO3(001) (STO) substrates were studied, and a phenomenological model in the high field limit was developed based on the 4/mmm point group. The derived longitudinal resistivity includes a four-fold as well as a two-fold symmetry term of the in-plane field angle, which can fit the experimental results well. In this study, to highlight the effects of misfit strain, AMR and PHE of LCMO thin films epitaxially grown on LaAlO3(001) substrates were studied, along either the [110] or the [100] direction. Both values are around a few percent, comparable to those measured in films on STO. Nevertheless, only tiny four-fold oscillations appear below the metal-insulator transition temperature Tp along the [110] direction, in contrast to the case of STO, where the four-fold term is prominent. The relationship between this four-fold symmetry and the misfit strain is then discussed in terms of the partial recovery of orbital magnetic moment. The mechanism for AMR and PHE in manganites then can be understood as an anisotropic percolation at metal-insulator transition resulting in the peak, and the spin-orbital coupling effect that accounts for the remnant far below Tp.