Magnetic Properties and Crystal Structure of DyMn_20_5 Nanoparticles Embedded in Mesoporous Silica

摘要

We synthesized DyMn_2O_5 nanoparticles with the nanometer size using mesoporous silica as template of nanoparticles. The size effects of the DyMn_20_5 nanoparticles were investigated through crystal structure analysis and magnetic measurement. The powder X-ray diffraction measurement revealed that the synthesized nanoparticles have orthorhombic structure with particle size of approximately 7 nm. The lattice constants for the nanoparticles deviated from those for the bulk crystal. The DyMn_2O_5 nanoparticles exhibited superparamagnetic behaviors. The evaluated Weiss temperature for the nanoparticles was positive value, whereas that for bulk crystal was negative one. The experimental results suggested that the distortion of crystallographic structure in the nanoparticles induced the changes in magnetic exchange interactions and magnetic frustration among manganese spins.