Large coercivity and small exchange bias in Mn_3O_4/MnO nanoparticles

摘要

Core/shell structured Mn_3O_4/MnO nanoparticles were prepared by arc evaporating metallic manganese in air. These nanoparticles show unconventional exchange bias phenomena, in which the Curie temperature of the ferrimagnetic Mn_3O_4 is lower than the Neel temperature of the antiferromagnetic MnO. The exchange bias field in Mn_3O_4/MnO nanoparticles is much smaller than that in Mn_3O_4/Mn nanoparticles, due to the weak interfacial exchange coupling. The coercivity of the Mn_3O_4 phase in nanoscale is almost three times greater than that of the bulk Mn_3O_4.