We conduct a theoretical study of the temperature dependence of the spin polarization ( P) and the magnetoresistance (MR) ratio using the double exchange (DE) model for ferromagnetic tunnel junctions with half-metallic systems. It is shown that the strong exchange coupling in the DE model plays an important role in the temperature dependence of both P and the MR ratio; their values can be less than the maximum values expected for half-metallic systems at low temperatures, and the MR ratio decreases more rapidly than P with increasing temperature. The calculated results, however, indicate that the MR ratio may still be large at high temperatures near the Curie temperature.

No abstract

No abstract

We theoretically study the temperature dependence of TMR in half-metallic manganite tunnel junctions. By performing numerical simulation based on linear response theory, it is shown that the effects of spin fluctuations on TMR are small and that the MR ratio remains at high temperatures near bulk TC. We deduce that the disappearance of the MR ratio at temperatures far below TC in experiments originates from a change in the interface electronic structure and magnetism.

No abstract