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GdFe₀.₅Cr₀.₅O₃ (GFCO) is a single-phase magnetoelectric multiferroic at temperatures close to ambient. Epitaxial thin films of this orthorhombic perovskite would offer the possibility of tuning its electrical and magnetic properties through control of strain and interface effects. Here, 200 nm thick GFCO thin films have been grown on (001) SrTiO3 substrates by solution synthesis and the microstructures have been investigated by cross-sectional transmission electron microscopy. The GFCO films are epitaxial but exhibit a mixture of three different orientation relationships in the form of domains ≈50 nm in diameter. Geometric analyses of the lattice matching show that the misfits for these domains would be tensile with magnitudes of less than 2 %. Pockets of a SrCrO4 reaction product form at the film/substrate interface and do not exhibit any simple orientation with the adjacent phases. The product morphology indicates that the outward diffusion of Sr is more rapid than the inward diffusion of Cr, and this is related to the microstructures of the surrounding phases. These data show that epitaxial films of GFCO can be obtained via this route, but careful control of process parameters would be required to produce single-domain films, and alternate substrates or buffer layers would be needed to inhibit SrCrO4 formation. 

Quantum materials have a fascinating tendency to manifest novel and unexpected electronic states upon proper manipulation. Ideally, such manipulation should induce strong and irreversible changes and lead to new relevant length scales. Plastic deformation introduces large numbers of dislocations into a material, which can organize into extended structures and give rise to qualitatively new physics as a result of the huge localized strains. However, this approach is largely unexplored in the context of quantum materials, which are traditionally grown to be as pristine and clean as possible. Here we show that plastic deformation induces robust magnetism in the quantum paraelectric SrTiO3, a property that is completely absent in the pristine material. We combine scanning magnetic measurements and near-field optical microscopy to find that the magnetic order is localized along dislocation walls and coexists with ferroelectric order along the walls. The magnetic signals can be switched on and off via external stress and altered by external electric fields, which demonstrates that plastically deformed SrTiO3 is a quantum multiferroic. These results establish plastic deformation as a versatile knob for the manipulation of the electronic properties of quantum materials. 

Magnetocaloric properties of TbCrO3 and TmCrO3 are reported and compared with those of the previously reported rare-earth chromites RCrO3 (R = Gd, Dy, Ho, and Er) and other perovskite-type oxides. The samples of TbCrO3 and TmCrO3 in this work were synthesized using a citrate gel combustion technique, and their magnetic properties were investigated and compared with those reported previously on RCrO3 (R = Gd, Dy, Ho, and Er). The Cr3+–Cr3+ ordering temperatures were found to strongly depend on the ionic radii of the rare-earth. By fitting the dc magnetization data with modified Curie–Weiss law including the Dzyaloshinsky–Moriya antisymmetric exchange interaction (D) and the symmetric exchange constant Je, spin canting angles (α) were obtained. In general, α was found to increase with the decreasing ionic radii of R3+ in RCrO3. The magnetocaloric properties investigated included the magnetic entropy change (−ΔS) for a given change in magnetic field (ΔH), the corresponding adiabatic temperature change (ΔTad), and their relative variations (ΔTad/ΔH) and (−ΔS/ΔH). It is observed that for RCrO3, (−ΔS) measured in the vicinity of the ordering temperature of R3+–R3+, varies almost as G2/3 where G is the de Gennes factor. Among RCrO3, GdCrO3 shows the largest value of (−ΔS/ΔH), because of its largest G factor and its magnitudes of (ΔTad/ΔH) and (−ΔS/ΔH) compare well with the reported values for the perovskites GdFeO3 and EuTiO3. These comparisons presented here provide useful information on the potential use of these materials in magneto-refrigeration technology.