Orbital and magnetic ordering and domain-wall conduction in ferrimagnet La_{5}Mo_{4}O_{16}

Abstract

We studied the ferrimagnet La_{5}Mo_{4}O_{16} with Mo ions on quasisquare lattices both experimentally and theoretically. We found that in addition to the antiferromagnetic ordering at T_{N}=200 K, a magnetic phase transition into a ferrimagnetic phase occurs at T_{s1}=60 K, which is caused by the orbital ordering of the Mo 4d states. We also found that the relatively small size of ferrimagnetic domains despite the large Ising anisotropy of the Mo spins are formed below T_{s1}, which are responsible for the relaxation behavior and the memory effect in the magnetization. Nonvolatile positive magnetoresistance observed in this compound below T_{s1} can be attributed to the fact that such magnetic domains and the electrical conduction along the domain walls disappear with the applied magnetic field.