Prog. Theor. Phys. Supplement No.159 (2005) pp. 77-81
Finite-Field Ground State of an S = 1 Anisotropic Antiferromagnetic Chain
1Department of Mechanical Engineering, Fukui University of
Technology, Fukui 910-8505, Japan
2Department of Physics, Niigata University, Niigata 950-2181, Japan
3Department of Physics, Tohoku University, Sendai 980-8578, Japan
4Faculty of Cross-Cultural Studies, Kobe University, Kobe 657-8501, Japan
We investigate, using numerical methods, the finite-field ground-state
properties of an S = 1 anisotropic antiferromagnetic chain
described by the Hamiltonian
H = ∑\nolimitsℓSℓx Sℓ+1x
+ Sℓy Sℓ+1y + ΔSℓz Sℓ+1z
+ D ∑\nolimitsℓ (Sℓz)2
- H ∑\nolimitsℓSℓz.
It is found that the magnetization jump anomaly (a first-order
phase transition) appears in the ground-state
magnetization curve when Δ= 5.0 and
-1.50 \lesssimD \lesssim1.05; in a certain region of D, the jump starts
from a finite value of the magnetization m
per spin. We also find that the a second-order phase transition between
commensurate and incommensurate gapless phases takes place in the
finite-field ground state. The critical point of this transition as well as
the values of m at the onset and end of the magnetization jump is summarized
in the m versus D phase diagram.
DOI : 10.1143/PTPS.159.77
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