Spin fluctuation in frustrated antiferromagnets

测量了核磁共振谱和核磁弛豫时间，研究了受阻反铁磁体的相变、自旋结构和涨落。三角晶格海森堡反铁磁体RbNiCl3的磁性。(1)证实了连续相变，发现中间相的温度范围仅为0.2K。(2)用包含高达二阶微扰的电四极相互作用解释了^&lt；87&gt；Rb的核磁共振分裂。(3)提出了一个关于低温相的自旋结构和自旋间相互作用的新模型。(4)通过测量每个相的弛豫时间，阐明了受挫反铁磁体中的特征涨落。测量了具有小易轴各向异性的三角晶格海森堡反铁磁体CsNiBr3(1)在顺磁相、组分无序相和三角有序相中的自旋晶格弛豫时间和电子自旋涨落。(2)发现三角形有序相中存在摆动涨落，并且这种涨落的双磁振子过程有助于核弛豫。(3)从弛豫时间揭示了顺磁相中的特征涨落。Kagome晶格反铁磁体AFE_3(OH)_6(SO_4)_2(A=NH_4，Na，K)的磁性质和涨落。(1)首次观察到Kagome晶格反铁磁体的连续相变。(2)通过测量Kagome晶格反铁磁体的~1H Nad^&lt；23&gt；Na的核磁共振谱，讨论了各相的自旋结构。

The NMR spectrum and the nuclear magnetic relaxation time have been measured to investigate the phase transition, the spin structure and the fluctuation in frustrated antiferromagnets.1. Magnetic properties in the triangular lattice Heisenberg antiferromagnet, RbNiCl_3.(1) Successive phase transitions were confirmed and the temperature range of the intermediate phase is found to be only 0.2K.(2) The NMR splitting of ^<87>Rb is explained by the electric quadrupole interaction including up to the second-order perturbation.(3) A new model was proposed about the spin structure in the low temperature phase and the interactions between spins.(4) A characteristic fluctuation in the frustrated antiferromagnets has been clarified by the measurement of the relaxation times in each phase.2. Spin-lattice relaxation time and electron spin fluctuation in the triangular lattice Heisenberg antiferromagnet with a small easy-axis anisotropy, CsNiBr_3(1) Spin-lattice relaxation times have been measured in the paramagnetic phase, the component disordered phase and the triangular ordered phase.(2) It was found that the swinging fluctuation exists in the triangular ordered phase and the two-magnon process of this fluctuation contributes to the nuclear relaxation.(3) The characteristic fluctuation in the paramagnetic phase was revealed from the relaxation time.3. Magnetic properties and fluctuation in Kagome Lattice Antiferromagnets AFe_3(OH)_6(SO_4)_2 (A=NH_4, Na, K).(1) Successive phase transitions were observed for the first time in the Kagome Lattice Antiferromagnets.(2) Spin structure in each phase was considered by the measurement of the NMR spectra of^1H nad ^<23> Na.(3) The characteristic fluctuation in Kagome Lattice Antiferromagnet was found.