Route to room-temperature ferromagnetic ultrathinSrRuO3films

Abstract

Experimental efforts to stabilize ferromagnetism in ultrathin films of transition metal oxides have so far failed, despite expectations based on density functional theory (DFT) and DFT+U. Here, we investigate one of the most promising materials, SrRuO3, and include correlation effects beyond DFT by means of dynamical mean field theory. In agreement with experiment we find an intrinsic thickness limitation for metallic ferromagnetism in SrRuO3 thin films. Indeed, we demonstrate that the realization of ultrathin ferromagnetic films is out of reach of standard thin-film techniques. Proposing charge carrier doping as a new route to manipulate thin films, we predict room temperature ferromagnetism in electron-doped SrRuO3 ultra thin films.

Atomic‐Scale Metal–Insulator Transition in SrRuO3 Ultrathin Films Triggered by Surface Termination Conversion

“…Specifically, for the N Ru = 4 case, the SrO‐terminated sample remains metallic, while the RuO 2 ‐terminated sample becomes highly insulating below 152 K. The N Ru = 3 film with RuO 2 ‐termination exhibits insulating behavior over the entire T range and a negligible FM signal. This behavior further implies that the RuO 2 ‐termination may facilitate an AF insulating phase …”

Quasiparticle self-consistent GW calculation of Sr2RuO4 and SrRuO3

“…For the bulk phase, LDA, LDA+U , and self-interaction correction (SIC) give the correct ferromagnetic solution although the calculated moment shows some deviations [17,[50][51][52]. For the thin film SRO113, however, the experimentally observed metal-to-insulator transition (MIT) and the ferromagnetic-to-nonmagnetic transition as a function of layer thickness are not consistently reproduced by these techniques [16,[53][54][55][56][57]. For example, the singlelayer SRO113 is predicted to be either ferromagnetic or nonmagnetic depending on the choice of the exchangecorrelation functional and the U values [53,[55][56][57].…”

Review on Electronic Correlations and the Metal-Insulator Transition in SrRuO3

“…Although U is not sufficiently large to induce the Mott insulating state, Δ and J can hinder the intersite and intrasite orbital hybridizations, which produces a hard gap in the minor t 2g band. However, the effect of Δ on the anomalous orbital ordering is not obvious (i.e., the in-plane compressive strain may or may not simply increase the energy of the major d xy band), and different authors have proposed different views (e.g., refer to Gu et al, 2012;Gupta et al, 2014;Si et al, 2015). In addition, the authors of some reports argue that electronphonon coupling is an important factor.…”

“…Because of the Hubbard repulsion and enhanced localization of orbitals, the loss of symmetry induced by Δ produces a prominent effective splitting Δ eff (Poteryaev et al, 2007(Poteryaev et al, , 2008. A DFT+DMFT study has shown the antiferromagnetic and insulating STO/SRO/STO with one-unit-cell thickness (Si et al, 2015), with a decent Δ eff between d xy and d xz,yz .…”