Cooling-field dependence of exchange bias effect in La_(0.45)Sr_(0.55)MnO_3 nanoparticles

摘要

Magnetic properties of 16 nm La_(0.45)Sr_(0.55)MnO_3 nanoparticles exhibit superparamagnetic blocking at 160 K with a ferromagnetic moment appearing in the antiferromagnetic state. The exchange interaction at the interface between canted ferromagnetic and antiferromagnetic regions within the nanoparticles leads to exchange bias, but the loop shift, coercivity, and remanence asymmetry all decrease strongly with increasing cooling field above 1T unlike a conventional ferromagnetic/antiferromagnetic exchange bias system. The observations imply a magnetization process involving coalescence of canted ferromagnetic clusters with increasing field, which reduces the interface area with the antiferromagnetic matrix.