Thermodynamic Properties of Three-Dimensional Orthogonal Dimer Model for SrCu${}_2$(BO${}_3$)${}_2$

Abstract

Effects of the inter-layer couplings for the orthogonal dimer system SrCu${}_2$(BO${}_3$)${}_2$ are discussed. The spin-gap $\Delta$ of the three-dimensional model is independent of the inter-layer couplings when they are small. Therefore at low temperatures ($T<\Delta$) thermodynamic properties are described well by the two-dimensional model. On the other hand at high temperatures the mean-field type scaling ansatz is useful to discuss the magnetic susceptibility for week inter-layer couplings. From fit of the magnetic susceptibility, the estimated coupling constants are J = 85 K for the nearest-neighbor couplings, $J^{{}^{\prime }}=54$ K for the next-nearest-neighbor couplings, and $J^{{}^{\prime \prime }}=8$ K for the inter-layer couplings. These parameters are consistent with the temperature dependence of the specific heat at low temperatures.

4 pages, 9 figures, to appear in Supplement B to J. Phys. Soc. Jpn {\bf 69} (2000) Proceedings of the International Workshop "Magnetic Excitations in Strongly Correlated Electrons"

Cited by in corpus (2)

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