We report on pulsed-field magnetization, Q -band electron spin resonance (ESR), and Na23 NMR measurements of the S=1 2 spin triangle clusters Na9 [Cu3 Na3 (H2 O)9 (α-X W9 O33) 2] (X=As and Sb). The pulsed-field magnetization shows pronounced hysteresis loops and magnetization steps including the half-step magnetization. The detailed magnetization behavior depends substantially on the diamagnetic heteroatom X. The angular dependence of ESR parameters necessitates Dzyaloshinskii-Moriya interaction. The temperature dependence of the Na23 spin-lattice relaxation rate, 1 T1, scales well to χ (T) T, where χ (T) is the static susceptibility. The spin-spin relaxation rate, 1 T2, increases rapidly for temperatures below 15 K due to dipolar interactions between the Na23 nuclei and Cu2+ spins. The two clusters exhibit a markedly different field dependence of 1 T1 at antilevel crossing points. The enhancement of 1 T1 is noticeable only for X=Sb. Since the spin configurations of both clusters are nearly the same, the dependence of magnetization and 1 T1 on X is ascribed to the strong coupling of the spins to a lattice vibration, leading to an enhanced mixing of the S=1 2 chiral state.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2008 Jan 8|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics