Epitaxial Growth of Complex Metal Oxides

6.5. Applications of epitaxial magnetic-oxide thin films

6.5.1. Magnetic tunnel junctions

An MTJ consists of two magnetic layers separated by a thin insulating layer. For magnetic layers that have large spin polarizations, large resistance changes occur through the junction when the moments of the magnetic layers switch from a parallel to an anti-parallel alignment. The first observation of MR in an all-oxide MTJ was for a La_0.67Sr_0.33MnO₃/SrTiO₃/La_0.67Sr_0.33MnO₃ junction, in which an MR of 83% was observed at 4 K (Figure 6.12) (Lu et al., 1996). Further structural improvements to the quality of the heterostructure and the addition of a CoO top pinning layer increased the MR of these MTJs to as high as 1850% at 4 K, corresponding to a spin polarization ...