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2008/04/07(Mon) 21:57

Direct Observation of Level Anticrossing in Spin Gap System CuHpCl

The aim of the present study is to fix the origin of double excited states revealed recently by neutron scattering measurements at zero field for a singlet ground state system Cu2(1,4-diazacycloheptane)2Cl4 (abbreviated as CuHpCl). For this, we employed high field ESR technique equipped with the vector network analyzer (VNA) and the superconducting magnet up to 15 T. Thanks to the high sensitivity, two distinct ESR absorptions were clearly observed at low temperature 1.5 K. Frequency dependent studies revealed that both modes have negative slope in the frequency-field diagram (red symbols in the figure), indicating that double excited states in CuHpCl corresponds to the triplet ones. This result provides a strong basis for understanding the controversial magnetism of CuHpCl. To proceed with this study further, lower frequency measurements than 50 GHz in high fields are highly desired.

Kyushu University: Y. Inagaki, T. Asano
IMR, Tohoku University: K. Koyama

Reference: Y. Inagaki et al., "Level anticrossing in a quantum spin liquid system CuHpCl with semi-metallic triplet band excitations", to be submitted.

網代芳民(京大院理),太田仁(神戸大分子フォトセ),菊池彦光(福井大工),Jean-Paul Boucher, Olivier Cepas, Timothy Ziman(フランスグルノーブル研究グループ)