Two-dimensional spin-12rectangular Heisenberg antiferromagnets: Simulation and experiment

Abstract

We have simulated and analyzed the susceptibility of a series of two-dimensional (2D) spin-1 2 rectangular Heisenberg antiferromagnetic (as well as mixed exchange antiferromagnetic/ferromagnetic) lattices as a function of J,J and temperature, where J is the dominant magnetic exchange interaction and J , the orthogonal interaction, is related to J by J = αJ , where α can vary from 0 to 1. Previous studies of the compounds pyrazineformatocopper(II) nitrate [Cu(pz)(HCO 2 )](NO 3 ), catena-2-aminopyrimidinedichlorocopper(II) [Cu(2-apm)Cl 2 ], and catena-pyrazinediazidocopper(II) [Cu(pz)(N 3 ) 2 ] indicated that these systems had 2D magnetic spin-spin interactions. However, there were no 2D models that could capture the behavior of any measurable bulk properties of the compounds. The previous authors fit the susceptibility data of the respective compounds to a 1D antiferromagnetic chain with a mean-field correction, or did not fit the data at all. We use the simulations to create this fit function in order to test the 2D model proposed for these spin systems.

Extremely well isolated two-dimensional spin- 12 antiferromagnetic Heisenberg layers with a small exchange coupling in the molecular-based magnet CuPOF

“…The resulting values of J, independently obtained by means of the aforementioned techniques, are in excellent agreement within experimental error. Additionally, the results of DC susceptibility and magnetic specific heat were analyzed in terms of a possible rectangular rather than a square magnetic in-plane structure [57,58] and are both fully consistent with the square-lattice case.…”

“…The existence of two distinct pyrazine molecules in the unit cell allows for the possibility of a rectangular magnetic lattice in which the exchange strengths (J and αJ, 0 α 1) along the a and b axes are different. This possibility has been tested by comparing the susceptibility data to the susceptibilities of a rectangular 2D QHAF [57,58] for various values of J and α. The square-lattice (α = 1) case gives by far the best fit and it is possible to rule out any rectangular contribution with α < 0.96.…”

Low-dimensional quantum magnetism in Cu(NCS)2 : A molecular framework material

“…As our quantum-chemical calculations suggested that the magnetic interactions were likely to be low dimensional, we carried out fits to the paramagnetic part of both the MPMS and EPR data sets (T > 14 K) using low-dimensional models, including both a 1D uniformchain model (fitting J 2 and g iso , fixing J 1 = J 3 = J 4 = 0) 70 and the 2D coupled chain or rectangular antiferromagnet model (fitting J 1 , J 2 and g iso , fixing J 3 = J 4 = 0). 8 We found that the 1D-and 2D-QHAFM models were able to fit both data sets well, but the 2D model was better able to account for the lower-temperature range (T < 30 K) [ Fig. 2(a,b)].…”

Interplay of Spin and Spatial Anisotropy in Low-Dimensional Quantum Magnets with Spin 1/2

“…In comparison with the m ≈ 0.3 derived for the square lattice, the significant reduction results from the strong enhancement of quantum fluctuations. While the ground-state properties of the rectangular lattice were already understood quite well, corresponding finite-temperature studies appeared only recently [76,77]. Quantum Monte Carlo simulations of the susceptibility and magnetization enabled to identify the realizations of the S = 1/2 HAF rectangular lattice, namely Cu(pz)Cl 2 (J/k B = 28 K, R = 0.3), Cu(pz)(N 3 ) 2 (J/k B = 15 K, R = 0.46) and Cu(2-apm)Cl 2 (2-apm = 2-amino-pyrimidine) with J/k B = 116.3 K and R = 0.084 [77].…”

“…[79,82], the difference in the maximum specific heat values for R = 1 and 0.7 is easily distinguishable. This approach was applied also in the determination of the 2D magnetic lattice in The comparison of the finite-temperature properties of the S = 1/2 HAF on the rectangular and zig-zag square lattice surprisingly revealed the identical behavior in the whole range of the spatial anisotropy R [77,82]. Thus, to decide which model is appropriate for the description of the real compound, first-principle studies are very important.…”