The processes of magnetization of ferrimagnetic Heisenberg chains of alternating spins are studied theoretically. Size-scaling analysis with the exact diagonalization of finite systems for ( S , s ) = (3/2,1) and (2,1) indicates a multi-plateau structure in the ground-state magnetization curve for S and s >1/2. The first plateau in the spontaneous magnetization can be explained classically: as originating from the Ising gap. In contrast, the second and higher ones must be originating from the quantization of the magnetization. It is also found that all of the 2 s plateaux, both classical and quantum ones, appear even in the isotropic case with no bond alternation.The processes of magnetization of ferrimagnetic Heisenberg chains of alternating spins are studied theoretically. Size-scaling analysis with the exact diagonalization of finite systems for ( S , s ) = (3/2,1) and (2,1) indicates a multi-plateau structure in the ground-state magnetization curve for S and s >1/2. The first plateau in the spontaneous magnetization can be explained classically: as originating from the Ising gap. In contrast, the second and higher ones must be originating from the quantization of the magnetization. It is also found that all of the 2 s plateaux, both classical and quantum ones, appear even in the isotropic case with no bond alternation.

arXiv:cond-mat/0010446Journal of Physics Condensed MatterNov 6, 200011 citations

Quantum magnetization plateaux of an anisotropic ferrimagnetic spin chain

Tôru Sakai, Kiyomi Okamoto

The magnetization curve of the $(S,s)=(1,1/2)$ ferrimagnetic alternating spin chain with single-ion anisotropy D is investigated with the numerical exact diagonalization of finite clusters and size-scaling analyses. The system has a plateau at (1/3) of the saturation moment, which corresponds to the spontaneous magnetization for $D=0.$ Varying D in the 1/3-magnetized ground state under the external field along the axis of D, a quantum phase transition is revealed to occur at the critical value $D/J=1.114\ifmmode\pm\else\textpm\fi{}0.001$ where the plateau vanishes. Except for the critical point, the plateau is always opening, but the mechanism is different between $D<{D}_{c}$ and $D>{D}_{c}.$ The change of mechanisms is an evidence to clarify that the plateau originates from the quantization of magnetization.The magnetization curve of the $(S,s)=(1,1/2)$ ferrimagnetic alternating spin chain with single-ion anisotropy D is investigated with the numerical exact diagonalization of finite clusters and size-scaling analyses. The system has a plateau at (1/3) of the saturation moment, which corresponds to the spontaneous magnetization for $D=0.$ Varying D in the 1/3-magnetized ground state under the external field along the axis of D, a quantum phase transition is revealed to occur at the critical value $D/J=1.114\ifmmode\pm\else\textpm\fi{}0.001$ where the plateau vanishes. Except for the critical point, the plateau is always opening, but the mechanism is different between $D<{D}_{c}$ and $D>{D}_{c}.$ The change of mechanisms is an evidence to clarify that the plateau originates from the quantization of magnetization.

arXiv:cond-mat/0204375Physical review. B, Condensed matterMay 16, 200260 citations

Quantum Magnetization Plateau of an Anisotropic Mixed Spin Chain

KIYOMI OKAMOTO

Jan 1, 20060 citations

The magnetization curve of the

(S,s)=(1,1/2)

ferrimagnetic alternating spin chain with single-ion anisotropy D is investigated with the numerical exact diagonalization of finite clusters and size-scaling analyses. The system has a plateau at (1/3) of the saturation moment, which corresponds to the spontaneous magnetization for

D=0.

Varying D in the 1/3-magnetized ground state under the external field along the axis of D, a quantum phase transition is revealed to occur at the critical value $D/J=1.114\ifmmode\pm\else\textpm\fi{}0.001$ where the plateau vanishes. Except for the critical point, the plateau is always opening, but the mechanism is different between

D<{D}_{c}

and

D>{D}_{c}.

The change of mechanisms is an evidence to clarify that the plateau originates from the quantization of magnetization.