Determination of Exchange Parameters for CaV_4O_9

Abstract

Magnetic susceptibility measured for CaV${}_4$O${}_9$ is analyzed by a method with high temperature expansion. The analysis is consistent with the $g$-value which is close to 2 and is observed by an ESR experiment. Four exchange parameters in a two-dimensional Heisenberg model are determined to represent CaV${}_4$O${}_9$. All the exchange parameters are about 500 K and strongly frustrated. The observed spin gap originates from the frustration.

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