Percolation Model of the Temperature Dependence of Exotic Magnetic Field in Doped Manganese Perovskites

We investigate the magnetic transitions in a (La_1-xB_x) _2/3Ca_1/3MnO₃ system, which consists of paramagnetic and ferromagnetic domains, based on a magnetic theoretical percolation model. In the mean-field approximation, the resistance as a function of temperature and magnetic field has been derived analytically and simulated numerically. It is found that the dependence of the critical temperature on magnetic field is linear when applied magnetic field is not too strong. Our theoretical predications are in good agreement with recent experimental observations.