Abstract
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 (θCW = −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.
Funder
Czech Research Infrastructures
Grantová Agentura Ceské Republiky
OP VVV
Subject
Condensed Matter Physics,Mathematical Physics,Atomic and Molecular Physics, and Optics