Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo2 F7

TY - JOUR

T1 - Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo2 F7

AU - Zeisner, J.

AU - Bräuninger, S. A.

AU - Opherden, L.

AU - Sarkar, R.

AU - Gorbunov, D. I.

AU - Krizan, J. W.

AU - Herrmannsdörfer, T.

AU - Cava, R. J.

AU - Wosnitza, J.

AU - Büchner, B.

AU - Klauss, H. H.

AU - Kataev, V.

N1 - Publisher Copyright: © 2019 American Physical Society.

PY - 2019/4/1

Y1 - 2019/4/1

N2 - We report high-frequency/high-field electron spin resonance (ESR) and high-field magnetization studies on single crystals of the bond-disordered pyrochlore NaCaCo2F7. Frequency- and temperature-dependent ESR investigations above the freezing temperature Tf∼2.4 K reveal the coexistence of two distinct magnetic phases. A cooperative paramagnetic phase, evidenced by a gapless excitation mode, is found along with 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, Phys. Rev. B 93, 014433 (2016)2469-995010.1103/PhysRevB.93.014433] is still sought after, our work motivates further theoretical investigations of the low-energy excitations in bond-disordered pyrochlores.

AB - We report high-frequency/high-field electron spin resonance (ESR) and high-field magnetization studies on single crystals of the bond-disordered pyrochlore NaCaCo2F7. Frequency- and temperature-dependent ESR investigations above the freezing temperature Tf∼2.4 K reveal the coexistence of two distinct magnetic phases. A cooperative paramagnetic phase, evidenced by a gapless excitation mode, is found along with 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, Phys. Rev. B 93, 014433 (2016)2469-995010.1103/PhysRevB.93.014433] is still sought after, our work motivates further theoretical investigations of the low-energy excitations in bond-disordered pyrochlores.

UR - https://www.scopus.com/pages/publications/85064127558

UR - https://www.scopus.com/pages/publications/85064127558#tab=citedBy

U2 - 10.1103/PhysRevB.99.155104

DO - 10.1103/PhysRevB.99.155104

M3 - Article

SN - 2469-9950

VL - 99

JO - Physical Review B

JF - Physical Review B

IS - 15

M1 - 155104

ER -