Electronic, magnetic and ferroelectric properties of multiferroic TlNiO3: A first principles study

The ground state structural, electronic, magnetic and ferroelectric properties of TlNiO3 are calculated by using density functional theory within the generalized gradient approximation. The calculations reveal that TlNiO3 has an antiferromagnetic ground state with a direct band gap of 0.53 eV. The local magnetic moment of Ni(1) and Ni(2) are 1.735 μB and 0.809 μB, respectively. Plots of the density of states (DOS) exhibit hybridization of Ni(1), Ni(2)-3d, and O-2p states. However, the calculated charge density and electron localization function (ELF) show a largely ionic character of the Ni-O bonds which is also supported by the anomaly in the calculated Born effective charges (BECs) with respect to the corresponding nominal ionic charges. We also find a spontaneous polarization of 2.13 μC/cm2 along the b-axis which is due to charge order induced by magnetic ordering.