Magnetic anisotropy and spin diffusion through spin disordered interfaces in magnetoresistive manganites

The magnetoresistance and magnetization of ceramic La(sub2/3)A(sub1/3)MnO(sub3) oxides were studied as a function of the grain size. The ceramics become harder magnetically when the particle size is reduced, showing a large magnetic anisotropy, rising with reduced grain size. A gradual increase of the low-field magnetoresistance is also observed. Both phenomena are thought to be closely linked and related to the existence of spin disorder at the grain boundaries.