Magnetism of (LaCoO3)n+(LaTiO3)n superlattices ( <

Abstract

LaCoO3 provides a poignant example of a transition metal oxide where the cobalt cations display multiple spin states and spin transitions and which continues to garner substantial attention. In this work, we describe first principles studies, based on DFT+U theory, of superlattices containing LaCoO3, specifically (LaCoO3)n+(LaTiO3)n for n = 1, 2. The superlattices show strong electron transfer from Ti to Co resulting in Co 2+ , significant structural distortions and a robust orbital polarization of the Co 2+ . We predict high-spin Co 2+ and a checkerboard (G-type) antiferromagnetic ground state. We provide a detailed analysis of the magnetic interactions and phases in the superlattices. We predict that ferromagnetic order on the Co2+ can be stabilized by hole doping (e.g., replacing La by Sr) which is rather unusual for Co 2+ cations.

Origin of the orbital polarization of Co2+ in La2CoTiO6 and ( Lee1, Park2, Ismail‐Beigi3 2021Phys. Rev. BSelf Cite8110View full textAdd to dashboardCite

“…As shown in Fig. 3(d), the P of the P 2 1 /n phase is always positive, as per our previous work [26]. The d z 2 band is significantly lower in energy when U Co = 0 and the material is insulating due to the energy splitting in the e g manifold (see the supplementary material for plots of the densities of states).…”

“…We begin with a discussion of the basic electronic and magnetic properties of LCO+LTO superlattices which is summarized in our previous studies [17,26]. In LCO+LTO superlattices as well as the double perovskite La 2 CoTiO 6 , there is a charge transfer from Ti 3+ (d 1 ) to Co 3+ (d 6 ), resulting in Ti 4+ (d 0 ) and Co 2+ (d 7 ).…”

“…We now highlight some basic facts about the Co 2+ spin states in the systems studied here. Since the electronic structure of Co 2+ is strongly dependent on the crystal structure, in this subsection we will focus only on the P 2 1 /n phase of the superlattice, which is the most stable phase we have found [17,26].…”

“…Indeed, it is strongly determined by the local octahedral distortions, i.e., the relative in-plane and out-of-plane Co-O bond lengths. In the superlattice, the out-of-plane Co-O bond is well elongated by the local electric field between Co and Ti ions [26]. Since the Co has interfaces at both sides and thus both of its out-of-plane Co-O bonds are elongated, the octahedral distortion of CoO 6 in (LCO) 1 +(LTO) 1 has standardized symmetry label A 1g + E g [27].…”

Robust Room Temperature Ferromagnetism In Cobalt Doped Graphene by Precision Control of Metal Ion Hybridization

“…Critical occupation number $${\rm{n}}_c^{\rm{e}}$$ is much smaller than 0.5, since ∆ 22 is much larger than ∆ 12 for Co d orbitals. [ 43 ] Note that ∆E is a maximum when $${\rm{n}}_c^{\rm{e}} = 0.5$$ which is close to the 0.5 e /Co doping value. Therefore, ∆ E is largest for 0.5 e /Co doping within DFT calculations.…”