Effects of temperature and electron effective mass on bias-dependent tunnelling magnetoresistance

In this paper, we study effects of temperature and electron effective mass within the barrier on the bias dependence and sign-change behavior of the tunneling magnetoresistance (TMR) in ferromagnetic junctions. A significant decrease of the tunneling magnetoresistance with elevating temperature is obtained, in accordance with experiments. In addition to the height of barrier potential (\phi) discussed in our previous papers, the electron effective mass (m_\rm B) within the barrier region is found to be another important factor that physically controls the sign-change behavior of the TMR. The critical voltage (V_\rm c) at which TMR changes sign will increase with \phi and decrease with m_\rm B, respectively. Furthermore, both the zero-bias TMR and V_\rm c will decrease if temperature rises. These results are hoped to be of practical use for experimental investigations.