Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo$_2$F$_7$
| Autor: | Zeisner, J., Bräuninger, S. A., Opherden, L., Sarkar, R., Gorbunov, D. I., Krizan, J. W., Herrmannsdörfer, T., Cava, R. J., Wosnitza, J., Büchner, B., Klauss, H. -H., Kataev, V. |
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| Rok vydání: | 2018 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 99, 155104 (2019) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.99.155104 |
| Popis: | We report high-frequency/high-field electron spin resonance (ESR) and high-field magnetization studies on single crystals of the bond-disordered pyrochlore NaCaCo$_2$F$_7$. Frequency- and temperature-dependent ESR investigations above the freezing temperature $T_f \sim 2.4$ K reveal the coexistence of two distinct magnetic phases. A cooperative paramagnetic phase, evidenced by a gapless excitation mode, is found as well as a spin-glass phase developing below 20 K which is associated with a gapped low-energy excitation. Effective $g$-factors close to 2 are obtained for both modes in line with pulsed high-field magnetization measurements which show an unsaturated isotropic behavior up to 58 T at 2 K. In order to describe the field-dependent magnetization in high magnetic fields, we propose an empirical model accounting for highly anisotropic ionic $g$-tensors expected for this material and taking into account the strongly competing interactions between the spins which lead to a frustrated ground state. As a detailed quantitative relation between effective $g$-factors as determined from ESR and the local $g$-tensors obtained by neutron scattering [Ross et al., Phys. Rev. B 93, 014433 (2016)] is still sought after, our work motivates further theoretical investigations of the low-energy excitations in bond-disordered pyrochlores. Comment: 9 pages, 6 figures |
| Databáze: | arXiv |
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