Orbital and magnetic ordering and domain-wall conduction in ferrimagnet La5Mo4 O16

We studied the ferrimagnet La5Mo4O16 with Mo ions on quasisquare lattices both experimentally and theoretically. We found that in addition to the antiferromagnetic ordering at TN=200 K, a magnetic phase transition into a ferrimagnetic phase occurs at Ts1=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 Ts1, which are responsible for the relaxation behavior and the memory effect in the magnetization. Nonvolatile positive magnetoresistance observed in this compound below Ts1 can be attributed to the fact that such magnetic domains and the electrical conduction along the domain walls disappear with the applied magnetic field.