Abstract
Alternate stacking of a highly conducting metallic layer with a magnetic triangular layer found in delafossite PdCrO2 provides an excellent platform for discovering intriguing correlated quantum phenomena. Thin film growth of delafossites may enable not only the tuning of the basic physical properties beyond what bulk materials can exhibit, but also the development of novel hybrid materials by interfacing with dissimilar materials, yet this has proven to be extremely challenging. Here, we report the epitaxial growth of metallic delafossite PdCrO2 films by pulsed laser epitaxy (PLE). The fundamental role of the PLE growth conditions, epitaxial strain, and chemical and structural characteristics of the substrate is investigated by growing under various growth conditions and on various types of substrates. While strain plays a large role in improving the crystallinity, the direct growth of epitaxial PdCrO2 films without impurity phases was not successful. We attribute this difficulty to both the chemical and structural dissimilarities with the substrate and volatile nature of the PdO sublayer, which make nucleation of the right phase difficult. This difficulty was overcome by growing CuCrO2 buffer layers before PdCrO2 films were grown. Unlike PdCrO2, CuCrO2 films were readily grown with a relatively wide growth window. Only a monolayer thick buffer layer was sufficient to grow the correct PdCrO2 phase. This result indicates that the epitaxy of Pd-based delafossites is extremely sensitive to the chemistry and structure of the interface, necessitating near perfect substrate materials. The resulting films are commensurately strained and show an antiferromagnetic transition at 40 K that persists down to as thin as 3.6 nm in thickness. This work provides key insights into advancing the epitaxial growth of the broader class of metallic delafossites for both studying the basic physical properties and developing new spintronic and computing devices.
Original language | English |
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Article number | 051104 |
Journal | APL Materials |
Volume | 8 |
Issue number | 5 |
DOIs | |
State | Published - May 1 2020 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The transport measurement and analysis were supported by the Computational Materials Sciences Program, and the optical measurement and analysis by W.S.C. was supported by the Basic Science Research Program through the National Research Foundation of Korea (Grant No. NRF-2019R1A2B5B02004546). C.S. was supported in part for obtaining the single crystal optical data by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (Grant No. NRF-2017M3D1A1040828). Single crystal optical measurements were performed using facilities at the IBS Center for Correlated Electron Systems, Seoul National University.
Funders | Funder number |
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U.S. Department of Energy | |
Office of Science | |
Basic Energy Sciences | |
Division of Materials Sciences and Engineering | |
Ministry of Science, ICT and Future Planning | NRF-2017M3D1A1040828 |
National Research Foundation of Korea | NRF-2019R1A2B5B02004546 |