Perovskite oxides ABO3 continue to be a major focus in materials science. Of particular interest is the interplay between A and B cations as exemplified by intersite charge transfer (ICT), which causes novel phenomena including negative thermal expansion and metal–insulator transition. However, the ICT properties were achieved and optimized by cationic substitution or ordering. Here we demonstrate an anionic approach to induce ICT using an oxyhydride perovskite, EuVO2H, which has alternating layers of EuH and VO2. A bulk EuVO2H behaves as a ferromagnetic insulator with a relatively high transition temperature (TC) of 10 K. However, the application of external pressure to the EuIIVIIIO2H bulk or compressive strain from the substrate in the thin films induces ICT from the EuIIH layer to the VIIIO2 layer due to the extended empty V dxy orbital. The ICT phenomenon causes the VO2 layer to become conductive, leading to an increase in TC that is dependent on the number of carriers in the dxy orbitals (up to a factor of 4 for 10 nm thin films). In addition, a large perpendicular magnetic anisotropy appears with the ICT for the films of <100 nm, which is unprecedented in materials with orbital-free Eu2+, opening new perspectives for applications. The present results provide opportunities for the acquisition of novel functions by alternating transition metal/rare earth layers with heteroanions.

This work was supported by CREST (JPMJCR1421, JPMJCR20R2), JSPS Core-to-Core Program (Grant No. JPJSCCA20200004), JSPS KAKENHI (Grants Nos. JP16H06438, JP17H04849, JP20H00384, JP21K05227, and JP 22H04914), Toyota Riken Scholar, the Murata Science Foundation, Ube Industries Foundation, Research Foundation for the Electrotechnology of Chubu, the Kyoto Technoscience Center, SEI Group CSR Foundation, the Kazuchika Okura Memorial Foundation, Tokuyama Science Foundation, Iketani Science and Technology Foundation, and Sumitomo Electric Industries. This work was also supported in part by JSPS Grant-in-Aid for Transformative Research Areas (A) “Hyper-Ordered Structures Science” (Grant No. JP21H05561).

Hiroshi Kageyama and Hiroshi Takatsu: et al.

Peer reviewed