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arXiv:cond-mat/0012278 · Physical review. B, Condensed matter

Alternating-spin ladders in a magnetic field: Formation of magnetization plateaux

A. Langari, Miguel Angel Martin-Delgado

Published Nov 1, 2000• 20 citations
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Abstract

We study numerically the formation of magnetization plateaux with the Lanczos method in two-leg ladders with mixed spins of magnitudes ${(S}_{1}{,S}_{2})=(1,1/2)$ located at alternating positions along the ladder and with dimerization $\ensuremath{\gamma}.$ For interchain coupling ${J}^{\ensuremath{'}}>0$ and $\ensuremath{\gamma}=0,$ we find normalized plateaux at $m=1/3$ starting at zero field and $m=1$ (saturation), while when $\ensuremath{\gamma}\ensuremath{\ne}0$ is columnar, another extra plateau at $m=2/3$ shows up. For ${J}^{\ensuremath{'}}<0,$ when $\ensuremath{\gamma}<{\ensuremath{\gamma}}_{c}{(J}^{\ensuremath{'}})$ we find no plateau while for $\ensuremath{\gamma}>{\ensuremath{\gamma}}_{c}{(J}^{\ensuremath{'}})$ we find four plateaux at $m=0,1/3,2/3,1.$ We also apply several approximate analytical methods (spin-wave theory, low-energy effective Hamiltonians, and bosonization) to understand these findings and to conjecture the behavior of ferrimagnetic ladders with a larger number of legs.

DOI
10.1103/physrevb.62.11725

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