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arXiv:cond-mat/0401264 · Physical Review B

Ferrimagnetic mixed-spin ladders in weak- and strong-coupling limits

D. N. Aristov, Mikhail N. Kiselev

Published Dec 2, 2004• 10 citations
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Abstract

We study two similar spin ladder systems with the ferromagnetic leg coupling. The first model includes two sorts of spins $s=1∕2$ and 1, and the second model comprises only $s=1∕2$ legs coupled by a ``triangular'' rung exchange. We show that the antiferromagnetic (AF) rung coupling destroys the long-range order and eventually makes the systems equivalent to the AF $s=1∕2$ Heisenberg chain. We study the crossover from the weak- to strong-coupling regime by different methods, particularly by comparing the results of the spin-wave theory and the bosonization approach. We argue that the crossover regime is characterized by the gapless spectrum and nonuniversal critical exponents are different from those in $XXZ$ model.

DOI
10.1103/physrevb.70.224402

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