Structural and spin-glass properties of single crystal J_eff = ½ pyrochlore antiferromagnet NaCdCo₂F₇

Author(s)

A. Kancko, G. Giester, R. H. Colman

Abstract

Weak bond disorder disrupts the expected spin-liquid ground-state of the ideal S = 1/2 Heisenberg pyrochlore antiferromagnet. Here we introduce a single crystal study of the structural and magnetic properties of the bond-disordered pyrochlore NaCdCo₂F₇. The magnetic susceptibility appears isotropic, with a large negative Curie-Weiss temperature (θ_CW = −108(1) K), however no magnetic order is observed on cooling until a spin-glass transition at T_f = 4.0 K. AC-susceptibility measurements show a frequency-dependent shift of the associated cusp in χ’ at T_f, that can be fitted well by the empirical Vogel-Fulcher law. The magnetic moment of μ_eff = 5.4(1) μ_B/Co²⁺ indicates a significant orbital contribution and heat capacity measurements show that down to 1.8 K, well below T_f, only S_mag ∼ 2/3 Rln(2) of the magnetic entropy is recovered, suggestive of residual continued dynamics. Structural and magnetism comparisons are made with the other known members of the NaA’’Co₂F₇ family (A″ = Ca²⁺, Sr²⁺), confirming the expected relationship between spin-glass freezing temperature, and extent of magnetic bond disorder brought about by the size mismatch between A-site ions.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Charles University Prague

Journal

Physica Scripta

Volume

98

ISSN

0031-8949

DOI

https://doi.org/10.1088/1402-4896/acdeb7

Publication date

07-2023

Peer reviewed

Yes

Austrian Fields of Science 2012

105116 Mineralogy, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Atomic and Molecular Physics, and Optics, Mathematical Physics, Condensed Matter Physics

Portal url

https://ucrisportal.univie.ac.at/en/publications/b2f177e1-8962-4fac-be00-459dff2131ce