中国物理B ›› 1997, Vol. 6 ›› Issue (3): 212-222.doi: 10.1088/1004-423X/6/3/007

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THEORETICAL CALCULATION OF THE MAGNETIC PROPERTIES IN DISORDERED GROUND STATE FOR SPIN-1/2 ANTIFERROMAGNET

杜安1, 魏国柱2   

  1. (1)College of Sciences, Northeastern University, Shenyang 110006, China; (2)International Centre for Materials Physics, Academia Sinica, Shenyang 110015, China, and College of Sciences, Northeastern University, Shenyang 110006, China
  • 收稿日期:1996-02-05 出版日期:1997-03-20 发布日期:1997-03-20

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   

  1. 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
  • Received:1996-02-05 Online:1997-03-20 Published:1997-03-20

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摘要： 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 λ'J, and in xy plane it is 2 λJ. In bond-operator representation, within the mean-field decoupling approximation, we have calculated the phase diagram for order-disorder phase transition about λ and λ' at 0 K, obtained the critical value, λc=0.292, within which the disordered phase is stable in two-dimensional case(λ'=0), and found that the disordered phase is always stable for λ'<1 in one-dimensional case(λ=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 λ and λ'.

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 $\lambda'$.

中图分类号:  (Quantized spin models, including quantum spin frustration)

  • 75.10.Jm
75.50.Ee (Antiferromagnetics)