Recent high field ESR studies of low-dimensional quantum spin systems in Kobe

Abstract

Recent advances in the high-field ESR studies of low-dimensional quantum spin systems in Kobe are presented. Among many systems studied, the results of S= 1 2 quasi-one-dimensional (1D) antiferromagnet BaCu 2(Si 1− x Ge x ) 2O 7 with the staggered field and S= 1 2 diamond chain system Cu 3OH 2(CO 3) 2 are discussed. As the interchain interaction is almost canceled in the BaCu 2(Si 1− x Ge x ) 2O 7 ( x=0.65) system, we have found that the field and temperature dependences of the linewidth and the resonance field obey the Oshikawa–Affleck (OA) ESR theory of 1D antiferromagnet. The effect of the interchain interaction from the x dependence measurement and the existence of the breather mode at low temperature are also discussed. On the other hand, the high-field ESR measurements at 1.8 K revealed the direct transition in Cu 3OH 2(CO 3) 2. The direct transition turned out to be anisotropic and it will be discussed in connection with the 1 3 magnetization plateau which is also anisotropic.