Designing ferromagnetism in early transition metal oxides in bulk and superlattice forms

The circumstances under which early transition metal oxides could exhibit ferromagnetism are determined using density functional plus single-site dynamical mean field methods. Particular attention is paid to the consequences of the GdFeO$_3$ distortion and other octahedral rotations. Ferromagnetism is favored by the combination of intermediate carrier concentration (formal valence $\sim d^{1.5}$) and large tilt angle. The decrease of GdFeO$_3$ distortion amplitude with hole doping away from $d^2$ is shown to keep the bulk solid solution La$_{1-x}$Sr$_x$VO$_3$ outside of the ferromagnetic regime. In superlattices such as (LaVO$_3$)$_m$(SrVO$_3$)$_1$, carrier concentration and tilt angle may be decoupled, potentially enabling ferromagnetism as suggested by experiment[1].\\[4pt] [1] U. L\"uders, W. C. Sheets, A. David, W. Prellier, and R. Fr\'esard, Phys. Rev. B 80, 241102(R) (2009).