自旋s=1的海森堡反铁磁链材料LiVGe2 O6的磁化率以及核磁共振实验表明该材料在临界温度约为22 K时由顺磁相转变为反铁磁N´eel相，且低温磁激发谱存在能隙。本文在已有模型哈密顿量的基础上提出了一个低能场论模型--Ginzburg-Landau理论来描述这一反铁磁链材料，并运用这一理论讨论了LiVGe2 O6由于自发对称性破缺导致的有限温度相变及相应的磁化率变化情况，理论计算很好地解释了现有的实验结果。%The susceptibility and nuclear magnetic resonance measurements on quasi-one-dimensional spin-1 Heisenberg antiferromagnet LiVGe2O6 indicate that this material shows a phase transition from paramagnetic state to antiferromagnetic N´eel state at about 22 K, and there exists a gap in the low-temperature magnetic excitation spectrum. Based on the model Hamiltonian of LiVGe2O6, we propose a low-energy field theory--Ginzburg-Landau theory for this compound. From this theory, we study the finite-temperature phase transition induced by spontaneous symmetry breaking and then calculate the finite-temperature susceptibility of LiVGe2O6. All the theoretical calculations are consistent with the experimental results.
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