Nanoscale ferroelastic twins formed in strained LaCoO ₃ films

Abstract

The coexistence and coupling of ferroelasticity and magnetic ordering in a single material offers a great opportunity to realize novel devices with multiple tuning knobs. Complex oxides are a particularly promising class of materials to find multiferroic interactions due to their rich phase diagrams, and are sensitive to external perturbations. Still, there are very few examples of these systems. Here, we report the observation of twin domains in ferroelastic LaCoO3 epitaxial films and their geometric control of structural symmetry intimately linked to the material’s electronic and magnetic states. A unidirectional structural modulation is achieved by selective choice of substrates having twofold rotational symmetry. This modulation perturbs the crystal field–splitting energy, leading to unexpected in-plane anisotropy of orbital configuration and magnetization. These findings demonstrate the use of structural modulation to control multiferroic interactions and may enable a great potential for stimulation of exotic phenomena through artificial domain engineering.

Strong Ferromagnetism Achieved via Breathing Lattices in Atomically Thin Cobaltites

“…[15][16][17] Perovskite-type cobaltite, LaCoO 3 (LCO), is a ferromagnetic insulator in tensile-strained thin films. [18][19][20][21] It has been studied intensively over last decade because the complete absence of power dissipation in a ferromagnetic insulator implies the lossless transfer of spin signals that circumvents the energy dissipation problem. [22,23] In LCO, the delicate interplay between the crystal field splitting (∆ CF ) and exchange interaction (J ex ) is extremely sensitive to strain.…”

“…b) Elemental specific XAS and XMCD for Co and Cu L ‐edges. The reference spectra for Co 3+[ 21 ] and Cu 2+[ 27 ] are shown as black dashed lines for comparison. The presence of a shoulder at ≈782 eV indicates that the LCO films substantially contain the low‐spin‐state Co 3+ ions, in consistent with previous report.…”

“…The presence of a shoulder at ≈782 eV indicates that the LCO films substantially contain the low‐spin‐state Co 3+ ions, in consistent with previous report. [ 21 ] The XMCD spectra were calculated from the difference between µ + and µ − divided by their sum, as described by ( µ + − µ − )/( µ + + µ − ), where µ + and µ − denote the XAS obtained from right‐handed circularly polarized and left‐handed circularly polarized X‐rays, respectively. XAS was collected in the total electron yield (TEY) mode at 10 K with applied fields of µ 0 H = ±5 T. d) Reflectivity curves for spin‐up ( R + ) and spin‐down ( R − ) polarized neutrons are shown as a function of wave vector q (upper panel).…”

Charge‐Transfer‐Induced Multivalent States with Resultant Emergent Magnetism in Transition‐Metal Oxide Heterostructures

“…Stoichiometric bulk LaCoO 3 (LCO) shows a nonmagnetic ground state. [ 23 ] Interestingly, an emergent ferromagnetism has been observed in their thin films. [ 20,24,25 ] Mechanisms underlying this exotic ferromagnetic state have been extensively investigated but remain disputable.…”

Magnetic domain engineering in SrRuO3 thin films

“…No matter what kinds of rotation patterns, they all share quite similar pseudocubic lattice with B site sitting in the center of oxygen octahedra and A site at the hole surrounded by eight octahedra to form ABO 3 stoichiometry. This structure character leads to easy and common formation of twin domains [16][17][18] . Furthermore, mismatch of rotation mode and rotation amplitude, which is widely observed in many heterointerfaces, can also result in the formation of twin domains 19,20 .…”