Impact of biaxial and uniaxial strain on V2O3

Abstract

Using first-principles calculations we determine the role of compressive and tensile uniaxial and equibiaxial strain on the structural, electronic and magnetic properties of V2O3. We find that compressive strain increases the energy cost to transition from the high-temperature paramagnetic metallic phase to the low-temperature antiferromagnetic insulating phase. This shift in the energy difference can be explained by changes in the V-V bond lengths that are antiferromagnetically aligned in the low temperature structure. The insights that we have obtained provide a microscopic explanation for the shifts in the metal-insulator transition temperature that have been observed in experiments of V2O3 films grown on different substrates.

Controlling metal–insulator transitions in reactively sputtered vanadium sesquioxide thin films through structure and stoichiometry

“…Previous results published in the literature have observed a correlation between the temperature and magnitude of the MIT and the c / a ratio of the lattice parameters 5 , 32 , 33 . Figure 8 shows a combined plot of the electrical resistance of the films fabricated for this study arranged according to their c / a values.…”

Structural and electrical properties of V2O3 thin films on c-plane Al2O3 fabricated by reactive-HiPIMS and dcMS techniques

“…The We attribute this reduction to small changes in the stoichiometry of the films with films grown at lower oxygen flows having a reduced oxygen content [32]. Furthermore, considering the in plane lattice constants of Al 2 O 3 which are lower than that of high temperature corundum V 2 O 3 , the coherent growth of films (at least for those showing an epitaxial nature), can be thought of to be under compressive in-plane strain [32], especially close to the interface [30]. However, the effect of variation in V 2 O 3 stoichiometry cannot be neglected which can further contribute to strain and will be discussed in a later section.…”

Positive and Negative Pressure Regimes in Anisotropically Strained V2O3 Films

“…These findings are consistent with recent theoretical studies suggesting that Cr doping induces orbital polarization and local distortions that stabilize the PI phase. [8,24] These local effects drive Cr-doped V 2 O 3 into the PI phase with little overall strain. This explains also previous X-ray absorption measurements showing differences in bandwidth and orbital occupation between the PM phases of pure V 2 O 3 and pressurized Cr-doped V 2 O 3 .…”

“…This explains also previous X-ray absorption measurements showing differences in bandwidth and orbital occupation between the PM phases of pure V 2 O 3 and pressurized Cr-doped V 2 O 3 . [5,6] To gain a deeper understanding of the effect of anisotropic strain in determining whether V 2 O 3 is driven into the positive or negative pressure regimes we calculated the energies of the AFI and PM phases as a function of strain using DFT, based on previous work by Wickramaratne et al [24] Since only magnetically ordered or non-magnetic phases can be modeled in DFT we used ferromagnetic coupling in the rhombohedral phase as a proxy for the PM phase. [39,40] We calculated the variation in energy of both ferromagnetic metal (FM) and AFI phases with anisotropic strains in the same crystallographic orientations with respect to the rhombohedral unit cell of the FM: 1) Equibiaxial strain along a/b with fixed c-axis.…”

“…Consequently, the trajectory of the phase transition follows the phase equilibrium line between the AFI and PM phases down to absolute zero. Different strains have also been considered theoretically, [24] arguing for a non-trivial dependence of the PM-AFI transition temperature on strain anisotropy, due to changes in length of one of the V-V bonds along the monoclinic b-axis that has a large impact on magnetic energy. Despite the large amount of work, several issues remain unclear: 1) That structural distortions stabilize the different phases in pure V 2 O 3 ?…”