Monte Carlo simulation of roughness effect on magnetic and magnetotransport behavior of La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 bilayers

In this work we address the study of the magnetic and magnetotransport properties of ferromagnetic (FM)/antiferromagnetic (AFM) La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 manganites bilayers by means of the standard Monte Carlo method. Simulations, implemented with a single spin flip Metropolis dynamics, were performed in the framework of a three-dimensional classical Heisenberg model. Four different superexchange interactions, with the two different types of ions Mn3+ and Mn4+ involved and the orbital differences accounting for the Mn3+ ions, were considered in the Hamiltonian. Likewise, terms dealing with magnetocrystalline anisotropy and the influence of an external applied magnetic field were also included. Samples were simulated having dimensions L×L×(dFM+dAFM) where L, measured in lattice parameter units, stands for the linear and lateral dimension along which periodic boundary conditions were implemented, whereas dFM and dAFM stand for the thicknesses of FM and AFM layers respectively with free boundary conditions. Different degrees of roughness at the interface were also simulated in order to analyze its influence on the magnetic and magnetotransport properties of the system. In particular, low-temperature results reveal a trend of the coercive field to increase with roughness contrary to the exchange bias field behavior, which tends to decrease. Both quantities are modulated by oscillations ascribed to the atomic disorder at the interface. Finally, the roughness effect upon the bilayer resistivity and on the metal-insulator temperature is also presented and discussed.