On the theory of quantum phase transition in dimerized antiferromagnets
Institute of Physics of the National Academy of Sciences of Ukraine, 46 Nauki Ave., Kyiv 03028, Ukraine
Bogolyubov Institute for Theoretical Physics of the National Academy of Sciences of Ukraine 14-b, Metrologicheskaya Str. Kiev, 03680, Ukraine
Received Octouber 23, 2009, revised November 10, 2009
The field-induced quantum magnetic phase transition in a dimerized spin crystal from its singlet ground state in the antiferromagnetic one is considered оn the assumption that the exchange interaction both on dimmers and between them is of antiferromagnetic
character. It is shown that because of this transition there occurs a magnetic polarization of the dimer ions and dimers as a whole. Spin orientations and spin projections in the magneto-ordered phase depend on the applied magnetic field, and magnetic susceptibility of this (in fact, quantum) state proves to be constant (as in classical Neel antiferromagnet) with changing orientations of sublattice spins.
PACS: 75.45.+j Macroscopic quantum phenomena in magnetic systems; PACS: 75.40.Cx Static properties.
Key words: dimer, quantum phase transition, order parameter.