Condensed Matter Physics, 2009, vol. 12, No. 3, pp. 435-447

Title: Spin models of quasi-1D quantum ferrimagnets with competing interactions
  N.B. Ivanov (Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee, 1784 Sofia, Bulgaria;
Fakultät für Physik, Universität Bielefeld, D-33501 Bielefeld, Germany)

We present a brief survey of the recent theoretical work related to generic Heisenberg spin models describing quasi-one-dimensional quantum ferrimagnets. The emphasis is on quantum chains and ladders with strong competing interactions, such as the frustrated J1-J2 chain with alternating (1, 1/2) spins, the spin-1/2 diamond chain with four-spin cyclic couplings, and some generic types of mixed-spin ladders with geometric frustration. As a rule, the discussed models exhibit rich quantum phase diagrams and provide some interesting examples of one-dimensional magnetic-paramagnetic quantum phase transitions. A number of open problems in the reviewed research area are discussed.

Key words: quantum spin chains, ferrimagnets, frustration
PACS: 75.10.Jm, 75.10Pq, 75.45.+j
Comments: Figs. 6, Refs. 88, Tabs. 0

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