Magnetization jumps and exchange bias induced by a partially disordered antiferromagnetic state in (FeTiO3)0.9-(Fe2O3)0.1

Magnetization jumps (MJs) and the exchange bias (EB) effect are simultaneously observed in the mixed-spin oxide (FeTiO3)0.9-(Fe2O3)0.1 at 2.0 K. Dc and ac susceptibility measurements confirm a reentrant spin glass phase with a partially disordered antiferromagnetic (PDA) state below the irreversibility temperature (Tir1⁄4 60 K). Antiferromagnetic (AFM) Fe3þ clusters are nested in AFM Fe2þ lattices forming a triangular lattice, in which 2/3 of the magnetic moments order antiferromagnetically with each other leaving the remaining 1/3 “confused.” This geometric frustration in the triangular lattice leads to a PDA state that is the ground state of the AFM triangular configuration. The PDA state, in the presence of a critical trigger field, evolves into a ferromagnetic (FM) state, and induces the AFM spins of the Fe2þ ions to enter a FM state, resulting in the MJs. Meanwhile, the FM spins of Fe2þ can serve as the pinned phase, and the AFM spins of Fe3þ can serve as the pinning phase, resulting in the EB effect. Thus, we point out that the PDA state is very likely to be at the origin of the MJs and the EB effect. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4881527]