Field-induced glassy state in disordered cluster antiferromagnets

Abstract

We investigate the role of antiferromagnetic spin clusters on the glassiness induced by uniform and random fields. We consider an antiferromagnetic disordered model that is treated within the replica method, resulting in an effective single-cluster problem. Our results show that regimes of weak and intermediate disorder are suitable for highly unusual phenomena. For the case of a uniform field, cluster polarization can favor a cluster spin-glass state, i.e., the magnetic field increases the freezing temperature at intermediate disorders. In addition, random fields introduce local perturbations that allow uncompensated cluster states, supporting cluster freezing even at very weak disorders. The theoretical framework presented here can be useful to the understanding of phenomena observed in magnetic glassy systems that have spin clusters as the building blocks instead of individual spins. In particular, we suggest that our results can help to explain the magnetic behaviour of the rare earth TbIn_0.99Mn_0.01O₃, which has been recently proposed to be composed of antiferromagnetic clusters, presenting a field-induced increasing of the freezing temperature.