We study the two dimensional quantum Heisenberg antiferromagnet on the square lattice with easy-axis exchange anisotropy by the semiclassical method called pure-quantum self-consistent harmonic approximation. In particular, we focus on the problem of the existence of a finite-temperature transition in such a model, and study the corresponding critical temperature as the spin value and the anisotropy vary. We find that an Ising-like transition characterizes the model even when the anisotropy is of the order of 10(-2) J (J being the intra-layer exchange integral). The good agreement found between our theoretical results and the experimental data for the compounds Rb2MnF4, K2MnF4, and K2NiF4 shows that the insertion of the easy-axis exchange anisotropy, with quantum effects properly taken into account, provides a quantitative description and explanation of the real system's critical behaviour.
The two-dimensional quantum Heisenberg antiferromagnet with Ising-like anisotropy / V. TOGNETTI; A. CUCCOLI; T. ROSCILDE; P. VERRUCCHI; R. VAIA. - In: BRAZILIAN JOURNAL OF PHYSICS. - ISSN 0103-9733. - STAMPA. - 30:(2000), pp. 697-700.
The two-dimensional quantum Heisenberg antiferromagnet with Ising-like anisotropy
TOGNETTI, VALERIO;CUCCOLI, ALESSANDRO;VERRUCCHI, PAOLA;
2000
Abstract
We study the two dimensional quantum Heisenberg antiferromagnet on the square lattice with easy-axis exchange anisotropy by the semiclassical method called pure-quantum self-consistent harmonic approximation. In particular, we focus on the problem of the existence of a finite-temperature transition in such a model, and study the corresponding critical temperature as the spin value and the anisotropy vary. We find that an Ising-like transition characterizes the model even when the anisotropy is of the order of 10(-2) J (J being the intra-layer exchange integral). The good agreement found between our theoretical results and the experimental data for the compounds Rb2MnF4, K2MnF4, and K2NiF4 shows that the insertion of the easy-axis exchange anisotropy, with quantum effects properly taken into account, provides a quantitative description and explanation of the real system's critical behaviour.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.