2023/08/30 by Guo, Yanbo, Hu, Xinzhe, Siddiquee, Hasan +5
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2308.16338
Induced by quenched disorder, random-singlet states occur in a variety of low-dimensional spin-1/2 antiferromagnets, some of them candidates for quantum spin liquids. Here we report measurements of the specific heat, magnetization, and magnetic susceptibility of nanocrystalline Sr21Bi8Cu2(CO3)2O41, a quasi-one-dimensional spin-1/2 antiferromagnet with alternating bonds. The results uncover the predominant presence of random-singlet spin pairs in this material, with a logarithmic probability distribution, P(J), of the renormalized, emergent exchange interaction, J, in zero magnetic field and P(J) proportional to 1/J in magnetic fields. We postulate that these unexpected J dependences, in contrast to the usual P(J) ∝ 1/Jγ with 0 < γ < 1, and possibly also the dichotomy, arise from the finite size of the nanocrystals. Scaling functions for the specific heat and magnetization reproduce our magnetocaloric-effect data, with no adjustable parameters.