Effects of Ga doping on magnetic and ferroelectric properties of multiferroic delafossite CuCrO2: Ab initio and Monte Carlo approaches

The effects of nonmagnetic impurity doping on magnetic and ferroelectric properties of multiferroic delafossite CuCrO2 are investigated by means of density functional theory calculations and Monte Carlo simulations. Density functional theory calculations show that replacing up to 30% of Cr3+ ions by Ga3+ ones does not significantly affect the remaining Cr-Cr superexchange interactions. Monte Carlo simulations show that CuCr1−xGaxO2 preserves its magnetoelectric properties up to x≃0.15 with a spiral ordering, while it becomes disordered at higher fractions. Antiferromagnetic transition shifts towards lower temperatures with increasing x and eventually disappears at x≥0.2. Our simulations show that Ga3+ doping increases the Curie-Weiss temperature of CuCr1−xGaxO2, which agrees well with experimental observations. Moreover, our results show that the incommensurate ground-state configuration is destabilized by Ga3+ doping under zero applied field associated with an increase of frustration. Finally, coupling between noncollinear magnetic ordering and electric field is reported for x≤0.15 through simulating P−E hysteresis loops, which leads to ferroelectricity in the extended inverse Dzyaloshinskii-Moriya model.