Study of magnetic field induced spin order in diluted antiferromagnetic states in a Ga doped α-Fe2O3 system prepared by a chemical route and air annealing

Abstract

We report the structural phase characterization and magnetic properties of the chemical routed α-Fe_2−xGa_xO₃ system (x: 0.28–0.60) after annealing at 800 °C in air. The synchrotron X-ray diffraction pattern and Raman spectra were used to characterize the rhombohedral structure (space group R3C) in the prepared samples. The composition of the samples was assigned from the results of energy dispersive analysis of the X-ray spectra. Magnetic properties of the samples were measured in the temperature range of 10–350 K and magnetic field range of 0 to ±70 kOe. A magnetic spin order transformation from the canted ferromagnetic state to weak antiferromagnetic state to surface paramagnetic state was noted as the measurement temperature is decreased to 10 K. Ga doping diluted the typical antiferromagnetic order at lower temperature in the hematite structure. The transition temperature and magnetic spin order associated with the transformation of different magnetic states were remarkably modified by the Ga content, field cooling process and field induced spin dynamics in the samples. The samples with higher Ga content indicated higher magnetic disorder, leading to a low moment and coercivity, and a prominent exchange bias effect. On the temperature scale, the samples exhibited variation of the ferromagnetic parameters from soft to hard character, reflecting the change of spin dynamics in different magnetic states.