Chemical Strain Engineering of Magnetism in Oxide Thin Films

Abstract

Transition metal oxides having a perovskite structure form a wide and technologically important class of compounds. In these systems, ferroelectric, ferromagnetic, ferroelastic, or even orbital and charge orderings can develop and eventually coexist. These orderings can be tuned by external electric, magnetic, or stress field, and the cross-couplings between them enable important multifunctional properties, such as piezoelectricity, magneto-electricity, or magneto-elasticity. Recently, it has been proposed that additional to typical fields, the chemical potential that controls the concentration of ion vacancies in these systems may reveal an efficient alternative parameter to further tune their properties and achieve new functionalities. In this study, concretizing this proposal, the authors show that the control of the content of oxygen vacancies in perovskite thin films can indeed be used to tune their magnetic properties. Growing PrVO thin films epitaxially on an SrTiO substrate, the authors reveal a concrete pathway to achieve this effect. The authors demonstrate that monitoring the concentration of oxygen vacancies through the oxygen partial pressure or the growth temperature can produce a substantial macroscopic tensile strain of a few percent. In turn, this strain affects the exchange interactions, producing a nontrivial evolution of Néel temperature in a range of 30 K.

Magnetism tailored by mechanical strain engineering in PrVO3 thin films

“…To get further insights on the role of the epitaxial strain on the magnetic properties of PrVO 3 films, we have performed first-principles simulations using Density Functional Theory (DFT). Consistently with previous studies [22], DFT correctly predicts that bulk PrVO 3 is a C-SO insulator in the ground state. Regarding the thin films, we find that the perovskite grows with the (001) Along with validating the experimentally measured trend for T N as a function of the applied epitaxial strain, our first-principles simulations also provide microscopic insights on the origin of this physical behavior.…”

“…This corresponds to the magnetic transition from paramagnetic (PM) state to an antiferromagnetic (AFM) phase transition. While for bulk PrVO 3 , the transition at T SO1 was previously ascribed to the onset of a C-type spin ordering (C-SO) of the canted vanadium moments [16,33], for epitaxial PrVO 3 thin films, the substrate-induced strain results in a G-type SO [22]. The AFM Néel temperature (named T SO1 here) for PVO/STO is however different from our previous report, where T N ∼ 80 K was reported [26].…”

“…This yields films grown along the orthorhombic (110) direction, in sharp agreement with experiments. We emphasize here that due to the presence of small domains in the films inducing a mechanical constraint[22], we have considered growth conditions with the (110) o direction forced to be orthogonal to the substrate (i.e. the film is not allowed to tilt).…”

Stimulating Oxide Heterostructures: A Review on Controlling SrTiO3‐Based Heterointerfaces with External Stimuli

“…This can be efficiently done in most oxides by controlling, e.g., the density of oxygen vacancies, which tend to exert tensile strain to the lattice. This was, for instance, the case for PrVO 3 films grown on STO where the presence of oxygen vacancies resulted in straining the lattice by a few percent, leading to significant changes in the magnetic properties . Although large strain values can be obtained in this way, the chemical strain pathway suffers from the risk of introducing side effects not stemming from the strain itself.…”

Synthesis and characterisation of fluorinated epitaxial films of BaFeO2F: tailoring magnetic anisotropyviaa lowering of tetragonal distortion

“…Within the last years, adopted approaches have been reported for uoride incorporation into epitaxially grown thin lms. [14][15][16][17][18][19] This does not only provide the opportunity to investigate such lms as a grain boundary free model system to study bulk related properties, but also to use strain engineering 20 to further modify materials' properties.…”