HALF-METALLIC ELECTRONIC-STRUCTURES OF COLOSSAL MAGNETORESISTANCE MANGANESE OXIDES

Using the virtual crystal approximation, we have studied electronic an d magnetic properties of the colossal magnetoresistance (CMR) La1-xBax MnO3 system at general doping concentrations. We have studied the chan ge of the electronic structure and the Fermi surface topology as a fun ction of the doping a: for 0.2 < x < 0.5, where the system is a ferrom agnetic metal with cubic structure. La1-xBaxMnO3 system undergoes a ph ase transition from a normal metallic ferromagnet to a half-metal at x = 0.33 where the CMR is observed. We have also studied the effect of the magnetic field and found that the magnetic field induces a half-me tallic transition, and so enhances the magnetoresistance.