¹H-NMR Study of the Random Bond Effect in the Quantum Spin System (CH₃)₂CHNH₃Cu(Cl_xBr_1−x)₃

Abstract

The spin–lattice relaxation rate T₁⁻¹ of ¹H-NMR has been measured in (CH₃)₂CHNH₃Cu(Cl_xBr_1−x)₃ with x=0.88, which is reportedly a gapped system with a singlet ground state from the previous macroscopic magnetization and specific heat measurements, in order to investigate the bond randomness effect microscopically in the gapped composite Haldane system (CH₃)₂CHNH₃CuCl₃. It was discovered that the spin–lattice relaxation rate T₁⁻¹ in the present system includes both fast and slow relaxation parts indicative of the gapless magnetic ground state and the gapped singlet ground state, respectively. We discuss the obtained results with the previous macroscopic magnetization and specific heat measurements together with the microscopic μSR experiments.