Evaluation of Exchange Interactions of the Spin Doughnut Mo_<75>V_<20>(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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The magnetic properties of the spin doughnut Mo_<75>V_<20>, which is a frustrated magnetic cluster with 20 spins, are studied by using the finite-temperature Lanczos method. Our model Hamiltonian consists of one ten-spin ring and two five-spin rings with nearest-neighbor antiferromagnetic couplings J and J". The five-spin rings are coupled to the ten-spin ring by an antiferromagnetic exchange interaction J' so as to form isosceles triangles of one J-bond and two J'-bonds. By fitting the theoretical magnetic susceptibility with the experimental one measured by Muller et al., the exchange parameters are estimated as J=388K, J'=163K, and J"=81K. The most interesting feature of this system is that the two five-spin rings behave as two free spins at low temperatures, although J'>J". We also study the temperature dependence of the specific heat and find three peaks at T〜J, J", and J'/100.
社団法人日本物理学会の論文
2007-08-15