Coupling and electrical control of structural, orbital and magnetic orders in perovskites

Abstract

Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials. The key to the functional electronic properties exhibited by perovskites is often the so-called Jahn-Teller distortion. For applications, an electrical control of the Jahn-Teller distortions, which is so far out of reach, would therefore be highly desirable. Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations. The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity. Thanks to the intimate coupling between Jahn-Teller distortions and electronic degrees of freedom, the electric field control of Jahn-Teller distortions is of general relevance and may find broad interest in various functional devices.

Electric Field Control of Jahn-Teller Distortions in Bulk Perovskites

“…This concept is related to an unusual coupling of lattice modes, giving rise in the free energy expansion to a trilinear term −λPR 1 R 2 linking the polar motion P to two independent nonpolar distortions R 1 and R 2 . Such a coupling was identified in various layered perovskites [8,9,[12][13][14][15], metal-organic framework [16,17], and can even appear in bulk ABO 3 perovskites [18,19]. Interestingly, in Ruddlesden-Popper compounds [9,20] and ABO 3 =A 0 BO 3 superlattices [21], this trilinear coupling appeared as a practical way to achieve electric control of nonpolar antiferrodistortive (AFD) motions associated with the rotation of the oxygen octahedra (i.e., monitoring P with an electric field will directly and sizeably tune the nonpolar modes R 1 and/or R 2 ).…”

“…Acting directly on the amplitude of the JT distortion might, alternatively, allow one to control the magnetic state with an electric field, as recently proposed independently in superlattices [14] and metal organic frameworks [16], or to control metal-insulator phase transitions.…”

“…ABO 3 perovskites often exhibit a nonpolar Pbnm ground state, resulting in a combination of three AFD motions (a − a − c þ pattern of rotations of the oxygen octahedra in Glazer's notation [22]). In this symmetry, Howard and Carpenter [23] pointed out that a JahnTeller distortion pattern automatically appears, which was later explained in terms of a trilinear coupling with AFD motions [14,24]. As a consequence, a Jahn-Teller distortion is not necessarily electronically driven but can, instead, arise from lattice mode couplings in which case a splitting of the electronic states may develop even in the absence of an electronic instability.…”

Ferroelectricity from coupled cooperative Jahn-Teller distortions and octahedral rotations in ordered Ruddlesden-Popper manganates

“…[20][21][22] They also couple to first-order Jahn-Teller (FOJT) lattice distortions, [23][24][25] but normally the combination of a tilt mode and FOJT mode, which is driven by an electronic degeneracy, will always maintain inversion unless additional symmetry reductions are achieved. 26 This concept was recently explored in metal-organic framework structures exhibiting the perovskite topology with FOJTactive transition metal ions, 27,28 and a symmetry-allowed trilinear energy term coupling a Jahn-Teller lattice distortion (Q 1 ) with a molecular rotation (Q 2 ) emerged. This anharmonic interaction induces both an electric polarization and a reasonable magnetoelectric response, owing to antiferromangetic ordering that is sensitive the antiferrodistortive Jahn-Teller pattern.…”

“…This anharmonic interaction induces both an electric polarization and a reasonable magnetoelectric response, owing to antiferromangetic ordering that is sensitive the antiferrodistortive Jahn-Teller pattern. Intriguingly, the number of inorganic oxides which exhibit ferroelectricity induced by this anharmonic interaction are scarce, 26,29 but it remains unclear whether that fact stems from limitations on the available coupling terms and coefficients, or rather that 'missing yet stable compounds' with such coupling have not been synthesized.…”