THEORETICAL CALCULATION OF THE MAGNETIC PROPERTIES IN DISORDERED GROUND STATE FOR SPIN-1/2 ANTIFERROMAGNET
DU AN (杜安)a, WEI GUO-ZHU (魏国柱)b
a College of Sciences, Northeastern University, Shenyang 110006, China; b International Centre for Materials Physics, Academia Sinica, Shenyang 110015, China, and College of Sciences, Northeastern University, Shenyang 110006, China
Abstract The spin-1/2 quantum antiferromagnet in three-dimensional space can be described by Heisenberg model:two nearest-neighbor spins with strong interaction in z direction consistitute a dimer, every dimer can be considered as a lattice site in the tetragonal lattice. In z direction, the exchange interaction between two nearest-neighbor dimers is $\lambda '$J, and in xy plane it is 2$\lambda$J. In bond-operator representation, within the mean-field decoupling approximation, we have calculated the phase diagram for order-disorder phase transition about $\lambda $ and $\lambda '$ at 0 K, obtained the critical value, $\lambda$c = 0.292, within which the disordered phase is stable in two-dimensional case($\lambda$ = 0), and found that the disordered phase is always stable for $\lambda'$<1 in one-dimensional case($\lambda$ = 0). For the disordered phase, the physical quantities, such as energy gap, ground-state energy, two-point correlation functions and correlation lengths in xy plane and in z direction, have been calculated as functions of parameters $\lambda$ and $\lambda'$.
Received: 05 February 1996
Accepted manuscript online:
PACS:
75.10.Jm
(Quantized spin models, including quantum spin frustration)
DU AN (杜安), WEI GUO-ZHU (魏国柱) THEORETICAL CALCULATION OF THE MAGNETIC PROPERTIES IN DISORDERED GROUND STATE FOR SPIN-1/2 ANTIFERROMAGNET 1997 Acta Physica Sinica (Overseas Edition) 6 212
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