Regensburg 2022 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 14: Cooperative Phenomena: Spin Structures and Magnetic Phase Transitions

MA 14.9: Vortrag

Dienstag, 6. September 2022, 11:45–12:00, H47

Spin structure of Frenkel excitons on Cu²⁺-ions in the antiferromagnet CuB₂O₄ revealed by magneto-absorption spectroscopy — •Dennis Kudlacik¹, Natalia E. Kopteva¹, Dimitri R. Yakovlev¹, Mikhail V. Eremin³, Alexey R. Nurmukhametov³, Manfred Bayer¹, and Roman V. Pisarev² — ¹Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany — ²St. Petersburg, Russia — ³Kazan, Russia

Frenkel excitons in magnetic insulators have attracted considerable interest in recent years as they allow the migration or transmission of a localized excitation. We have investigated this property which is reflected in the Davydov splitting of the exciton in the antiferromagnet copper metaborate, CuB₂O₄ [1]. This magnetic insulator consists of two weakly interacting sublattices of Cu²⁺ ions. Below the Neel temperature of T_N=21 K its magnetic structure is dominated by the antiferromagnetic order of the 4b sublattice which comprises 4 Cu²⁺ ions twice degenerate in spin resulting in the formation of 8 collective charge-spin Frenkel-Davydov excitations. From a comparison of the experimental data with the results of the theoretical model we define the parameters of Frenkel exciton states, determine the electron-energy transfer between antiferromagnetically coupled copper spins as well as the anisotropic Cu²⁺ g-factors of ground and excited states.
[1] N. E. Kopteva et al., Phys. Rev. B 105, 024421 (2022).