Effects of Ga doping on magnetic and ferroelectric properties of multiferroic delafossite CuCrO 2 : Ab initio and Monte Carlo approaches

International audienceThe effects of nonmagnetic impurity doping on magnetic and ferroelectric properties of multiferroic delafossite CuCrO 2 are investigated by means of density functional theory calculations and Monte Carlo simulations. Density functional theory calculations show that replacing up to 30% of Cr 3+ ions by Ga 3+ ones does not significantly affect the remaining Cr-Cr superexchange interactions. Monte Carlo simulations show that CuCr 1−x Ga x O 2 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 Ga 3+ doping increases the Curie-Weiss temperature of CuCr 1−x Ga x O 2 , which agrees well with experimental observations. Moreover, our results show that the incommensurate ground-state configuration is destabilized by Ga 3+ 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