Effect of the exchange interaction anisotropy on the magnetic quantum phase transitions in dimerized antiferromagnets
T.I. Lyashenko1, V.M. Kalita1,2, and V.M. Loktev1,3
1National Technical University of Ukraine “KPI”, 37 Peremogy Ave., Kiev 03056, Ukraine
2Institute of Physics of the National Academy of Sciences 46 Nauki Ave., Kiev 03028, Ukraine
3Bogolubov Institute for Theoretical Physics, NAN of Ukraine, 14b Metrologichna Str., 03143 Kiev, Ukraine
Received February 16, 2017, revised April 4, 2017.
A theoretical description of the induced by magnetic field the quantum phase transition in a dimerized antiferromagnet is carried out. It is shown such a description can be done by the founding of the Lagrange function minimum, which depends on the parameters of the ground-state wave function of the crystal. It was found that the transition from the initial dimer singlet state in the state with non-collinear spin orientations in a crystal takes place and is like to a phase transition of the order-order type. It is also shown that in the case of uniaxial anisotropy the position of the quantum transition critical point is affected by the dimer internal spin-spin interactions. Wherein anisotropic spin-spin interactions between the dimers, as in the case of classic Néel antiferromagnets, shift only the spin-flip transition point from the non-collinear antiferromagnetic phase to the ferromagnetic one.
PACS: 75.10.Jm Quantized spin models, including quantum spin frustration; PACS: 75.30.Kz Magnetic phase boundaries; PACS: 75.30.Gw Magnetic anisotropy; PACS: 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.); PACS: 75.45.+j Macroscopic quantum phenomena in magnetic systems; PACS: 75.50.Ee Antiferromagnetics.
Key words: magnetic dimers, magnetic quantum phase transition, magnetic anisotropy, antiferromagnetics.