Study of surface magnetism, exchange bias effect, and enhanced ferromagnetism in α-Fe_(1.4)Ti_(0.6)O_3 alloy

摘要

Magnetic properties of mechanical alloyed α-Fe_(1.4)Ti_(0.6)O_3 were studied at broad scale of temperatures, starting from room temperature down to 5 K. Morin transition of the base compound α-Fe_2O_3 was not observed after Ti doping. Enhanced ferromagnetism and exchange bias effect were exhibited in the alloyed compound α-Fe_(1.4)Ti_(0.6)O_3. The observations were examined from different aspects of the alloying process, e.g., magnetic solution (spin ordering) at the interfaces of rhombohedral planes and core-shell structure of the nano-grains. Interfacial magnetic modifications were seen to be affected by the factors associated with grain size variation during alloy formation and thermal annealing of the alloy. Detailed analyses were made to understand the surface magnetism and exchange bias effect in the samples. Magnetic features of the present samples in many cases were found to be unconventional in comparison with the simple grain size effect of magnetic particles.