Frustrated magnetism in the Heisenberg pyrochlore antiferromagnets AYb2X4 ( A=Cd , Mg; X=S , Se)
Tomoya Higo, Kensuke Iritani, Mario Halim, Wataru Higemoto, Takashi U. Ito, Kentaro Kuga, Kenta Kimura, Satoru Nakatsuji
Physical review B
Our polycrystalline sample study on the Yb-based chalcogenide spinels AYb_2X_4 (A = Cd, Mg, X = S, Se) has revealed frustrated magnetism due to the antiferromagnetically coupled Heisenberg spin on the pyrochlore lattice. Our crystal electric field analysis indicates the Yb ground state has nearly Heisenberg spins with a strong quantum character of the ground doublet. All the materials exhibit an antiferromagnetic order at 1.4-1.8 K, much lower temperature than the antiferromagnetic exchange
... ling scale of ∼ 10 K. The magnetic specific heat C_ M shows a T^3 dependence, indicating the gapless feature in the Yb-based chalcogenide spinels. The magnetic entropy change much smaller than R ln 2 below the Néel temperature and the small local magnetic field estimated from the μSR measurements strongly suggest the significantly reduced size of the ordered moment in comparison with the bare moment size 1.33 μ_ B/Yb supporting strong fluctuations in the commensurate and incommensurate ordered states in CdYb_2S_4 and MgYb_2S_4, respectively.