Magnetic resonance study of rare-earth titanates

Scientific paper - Original scientific paper

• Author: A. Najev
• Author: S. Hameed
• Author: A. Alfonsov
• Author: J. Joe
• Author: V. Kataev
• Author: M. Greven
• Author: M. Požek
• Author: D. Pelc
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

We present an electron spin resonance (ESR) and nuclear magnetic resonance (NMR) study of rare-earth titanates derived from the spin-1/2 Mott insulator YTiO3. Measurements of single-crystalline samples of (Y, Ca, La)TiO3 in a wide range of isovalent substitution (La) and hole doping (Ca) reveal several unusual features in the paramagnetic state of these materials. ESR of the unpaired Ti electron shows broad resonance lines at all temperatures and substitution/doping levels, which we find to be caused by short electronic spin-lattice relaxation times. We model the relaxation as an Orbach process that involves a low-lying electronic excited state, which enables the determination of the excited-state gap from the temperature dependence of the ESR linewidths. We ascribe the small gap to Jahn-Teller splitting of the two lower Ti 𝑡2𝑔 orbitals. The value of the gap closely follows the Curie temperature 𝑇𝐶. 89Y NMR demonstrates a clear discrepancy between the static and dynamic local magnetic susceptibilities, with deviations from Curie-Weiss behavior at temperatures far above 𝑇𝐶, consistent with the electronic gap detected with ESR. No significant changes are observed by NMR close to 𝑇𝐶, but suppression of fluctuations is detected in the NMR spin-lattice relaxation time at temperatures of about 3×𝑇𝐶. Additionally, the nuclear spin-spin relaxation rate shows an unusual peak in dependence on temperature for all samples. These results provide insight into the interplay between orbital and spin degrees of freedom in rare-earth titanates and indicate that full orbital degeneracy lifting is associated with ferromagnetic order.

• Keywords (english): nuclear magnetic resonance; NMR; electron spin resonance; ESR
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review B
• Numbering: vol. 109, no. 17, 174406
• p-ISSN: 2469-9950
• e-ISSN: 2469-9969
• DOI: https://doi.org/10.1103/PhysRevB.109.174406
• URN:NBN: urn:nbn:hr:217:824825
• Publication: 2024-01-01
• Project: Number: KK.01.1.1.02.0013; Title (croatian): Centar za Napredna Istraživanja Kompleksnih Sustava; Title (english): Centre for Advanced Research of Complex Systems; Acronym: CeNIKS; Leader: Mihael Srđan Grbić; Jurisdiction: eu; Funding stream: European Regional Development Fund
• Document URL: https://link.aps.org/doi/10.1103/PhysRevB.109.174406
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2024 American Physical Society. Received 23 November 2022. Revised 21 November 2023. Accepted 18 April 2024. Published 2 May 2024.
• Created on: 2024-07-25 11:29:07