Strain-induced creation and switching of anion vacancy layers in perovskite oxynitrides

Using strain to control oxynitride properties. 京都大学プレスリリース. 2020-12-01.原子空孔の配列を制御する新手法の発見. 京都大学プレスリリース. 2020-12-02.Perovskite oxides can host various anion-vacancy orders, which greatly change their properties, but the order pattern is still difficult to manipulate. Separately, lattice strain between thin film oxides and a substrate induces improved functions and novel states of matter, while little attention has been paid to changes in chemical composition. Here we combine these two aspects to achieve strain-induced creation and switching of anion-vacancy patterns in perovskite films. Epitaxial SrVO3 films are topochemically converted to anion-deficient oxynitrides by ammonia treatment, where the direction or periodicity of defect planes is altered depending on the substrate employed, unlike the known change in crystal orientation. First-principles calculations verified its biaxial strain effect. Like oxide heterostructures, the oxynitride has a superlattice of insulating and metallic blocks. Given the abundance of perovskite families, this study provides new opportunities to design superlattices by chemically modifying simple perovskite oxides with tunable anion-vacancy patterns through epitaxial lattice strain

Magnetocrystalline anisotropy in single-crystal Co-Ni-Al ferromagnetic shape-memory alloy

The single-variant state and the magnetocrystalline anisotropy in a single crystal Co 41 Ni 32 Al 27 ferromagnetic shape memory alloy (FSMA) have been investigated. After applying compressive stress, the single-variant state was confirmed by optical micrograph and linear thermal expansion measurements. In the heating process for the single-variant martensite phase, the shrinkage of about 7% takes place at the reverse transformation temperature. From the magnetization curves along the c-, a-axes and the [110] M directions in the single-variant state, the c-axis is determined to be the hard axis and the magnetocrystalline anisotropy constant in the single crystal Co 41 Ni 32 Al 27 0 martensite phase is evaluated to be 3:2 Â 10 5 J/m 3 at 5 K