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Magnetic properties and interfacial phenomena of epitaxial perovskite oxides depend sensitively on parameters such as film thickness and strain state. In this work, epitaxial La 0.67 Sr 0.33 CoO 3 (LSCO)/La 0.67 Sr 0.33 MnO 3 (LSMO) bilayers were grown on NdGaO 3 (NGO) and LaAlO 3 (LAO) substrates with a fixed LSMO thickness of 6 nm, and LSCO thickness (t LSCO ) varying from 2 to 10 nm. Soft x-ray magnetic spectroscopy revealed that magnetically active Co 2+ ions that strongly coupled to the LSMO layer were observed below a critical t LSCO for bilayers grown on both substrates. On LAO substrates, this critical thickness was 2 nm, above which the formation of Co 2+ ions was quickly suppressed leaving only a soft LSCO layer with mixed valence Co 3+ /Co 4+ ions. The magnetic properties of both LSCO and LSMO layers displayed strong t LSCO dependence. This critical t LSCO increased to 4 nm on NGO substrates, and the magnetic properties of only the LSCO layer displayed t LSCO dependence. A non-magnetic layer characterized by Co 3+ 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.
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The Proximity Effect and Critical Field Behavior of Re/Al Bilayers
Abstract We report the perpendicular critical field Hc2properties of disordered Re-Al bilayers via magnetotransport measurements. The bilayers consisted of a dRe= 3 nm bottom layer of Re and an upper Al layer with thickness varying between dAl= 0-3 nm. We find that in this range of Al thicknesses, the bilayer transition temperature Tcincreases with increasing Al thickness, although their monolayer counterparts have TRec> TAlc. Furthermore, Hc2of the bilayers has a local maximum at an Al coverage of 1.5 nm with a critical field that is 50% larger than that of the standalone 3 nm Re film. At higher Al thicknesses Hc2drops rapidly but remains more than an order of magnitude greater that that of comparable thickness standalone Al film. Our data show that a thin, disordered Re under-layer can dramatically increase the magnetic field tolerance of the Al over-layer. This would allow one to retain the desirable chemical and metallurgical properties of Al without sacrificing high field compatibility in quantum circuits, such as topological qubit devices.
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- Award ID(s):
- 2302420
- PAR ID:
- 10573874
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Materials Research Express
- ISSN:
- 2053-1591
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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