Half-metallic ferromagnetism in double perovskites Pb2XX'O6 (X = V and Cr and X' = Zr and Hf)

The structural, magnetic, and electronic properties of Pb-based double perovskite, Pb2XX'O6 (X = V and Cr and X' = Zr and Hf), have been studied in this paper. This study uses the first-principal projector augmented wave (PAW) potential within the generalized gradient approximation (GGA) as well as considering the on-site Coulomb re-pulsive interaction (GGA+U). The structure of these Pb-based double perovskite is calculated with four magnetic states, antiferromagnetic (AFM), ferromagnetic (FM), ferrimagnetic (FiM), nonmagnetic (NM), and then we compare the energy of these states to find the most stable state. We quickly discovered that all these materials have a lower energy level at the ferromagnetic state, especially Pb2VZrO6 which has an energy difference between AFM and FM state of 120 meV. By analyzing the density of states (DOS) and its magnetic moment, we further discovered that all these materials are half-metallic ferromagnetic (HM-FM). They have an integer magnetic moment because all these materials have a band gap in the spindown channel. Under GGA + U, the band gap still exists and enlarges, and the V series materials became more stable because of the larger differences between the state of AFM and FM, while the Cr series have the opposite. Lastly, we calculate the electron configuration of V, Cr, Zr, and Hf under GGA and GGA + U calculations in this paper. The HM characteristics of the band gap in one of its spin channels and its ferromagnetic nature mean that there are huge potential applications of these new compounds in spintronics.