Colossal Magnetoresistance CMR in Perovskite Oxomanganates

After the discovery of GMR in metallic multilayers in the late 1980s, MR effects even larger than GMR were reported in 1993 by von Helmolt etalS and others ° and a little later (in 1994) by Jin in a class of 

The TMR of a junction is related to the spin polarisation of the two electrodes. In the simple model of Julliere the TMR ratio, i.e. the ratio of the resistance change between the antiparallel and the parallel state (R l - R ) to the resistance in the parallel state Ri-f, is directly related to the spin polarisation of the two ferromagnetic electrodes by  

According to Equation 5.3, materials with high spin polarisation will lead to huge TMR ratios. 

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