Magnetization plateaux and jumps in a class of frustrated ladders: A simple route to a complex behaviour
Institut für Theoretische Physik, ETH-Hönggerberg, 8093 Zürich, Switzerland
2 Laboratoire de Physique Quantique, Université Paul Sabatier, 31062 Toulouse Cedex, France
Revised: 30 December 1999
Published online: 15 May 2000
We study the occurrence of plateaux and jumps in the magnetization curves of a class of frustrated ladders for which the Hamiltonian can be written in terms of the total spin of a rung. We argue on the basis of exact diagonalization of finite clusters that the ground state energy as a function of magnetization can be obtained as the minimum - with Maxwell constructions if necessary - of the energies of a small set of spin chains with mixed spins. This allows us to predict with very elementary methods the existence of plateaux and jumps in the magnetization curves in a large parameter range, and to provide very accurate estimates of these magnetization curves from exact or DMRG results for the relevant spin chains.
PACS: 75.10.Jm – Quantized spin models / 75.40.Cx – Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) / 75.45.+j – Macroscopic quantum phenomena in magnetic systems
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000