Novel magnetic oxides for refrigerants and tunneling magnetoresistance materials

Perovskite－type compounds are a very interesting kind of material that may exhibit high－Tc superconductivity , ferroelectricity, piezoelectricity or colossal magnetoresistance (CMR). In recent years, large magnetic entropy change and tunneling magnetoresistance effects in magnetic perovskite－type compounds have been observed. Through investigations of the dependence of these effects on particle size and structure we have discovered that the significant entropy change, easily tuned Curie temperature and good chemical stability of perovskite－type compounds make them suitable candidates for magnetic refrigerants. Except for their intrinsic magnetoresistance near the Curie temperature, we find that the tunneling magnetoresistance is insensitive to temperature changes over a very wide low temperature range.