Plateau of the Magnetization Curve of the S=1/2 Ferromagnetic-Ferromagnetic-Antiferromagnetic Spin Chain

摘要: I analytically study the plateau of magnetization curve at $M/M_{\rm S} = 1/3$ (where $M_{\rm S}$ is saturation magnetization) one-dimensional $S=1/2$ trimerized Heisenberg spin system with ferromagnetic ($J_{\rm F}$)-ferromagnetic F}$)-antiferromagnetic A}$) interactions $T=0$. use bosonization technique for fermion representation Hamiltonian through Jordan-Wigner transformation. The appears when $\gamma \equiv J_{\rm F}/J_{\rm A} \allowbreak \gamma_{\rm C}$, where critical value $\gamma_{\rm C}$ estimated as C} 5 \sim 6$. behavior width near Kosterlitz-Thouless type. present theory well explains numerical result by Hida.