Strain- and thickness-dependent magnetic properties of epitaxial La0.67Sr0.33CoO3/La0.67Sr0.33MnO3 bilayers

• Published in: Journal of applied physics Vol. 132; no. 19
• Main Authors: Feng, Mingzhen, Ahlm, Nolan J., Kane, Alexander M., Chiu, I-Ting, Sasaki, Dayne Y., Shafer, Padraic, N'Diaye, Alpha T., Mehta, Apurva, Takamura, Yayoi
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 21.11.2022; American Institute of Physics (AIP)
• Subjects: Applied physics; Cobalt; Epitaxy; Film thickness; Magnetic properties; Magnetic spectroscopy; Magnetism; MATERIALS SCIENCE; Memory devices; Parameter sensitivity; Perovskites; Soft x rays; Substrates
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0122009

Magnetic properties and interfacial phenomena of epitaxial perovskite oxides depend sensitively on parameters such as film thickness and strain state. In this work, epitaxial La0.67Sr0.33CoO3 (LSCO)/La0.67Sr0.33MnO3 (LSMO) bilayers were grown on NdGaO3 (NGO) and LaAlO3 (LAO) substrates with a fixed LSMO thickness of 6 nm, and LSCO thickness (tLSCO) varying from 2 to 10 nm. Soft x-ray magnetic spectroscopy revealed that magnetically active Co2+ ions that strongly coupled to the LSMO layer were observed below a critical tLSCO for bilayers grown on both substrates. On LAO substrates, this critical thickness was 2 nm, above which the formation of Co2+ ions was quickly suppressed leaving only a soft LSCO layer with mixed valence Co3+/Co4+ ions. The magnetic properties of both LSCO and LSMO layers displayed strong tLSCO dependence. This critical tLSCO increased to 4 nm on NGO substrates, and the magnetic properties of only the LSCO layer displayed tLSCO dependence. A non-magnetic layer characterized by Co3+ ions and with a thickness below 2 nm exists at the LSCO/substrate interface for both substrates. The results contribute to the understanding of interfacial exchange spring behavior needed for applications in next generation spintronic and magnetic memory devices.