2D XY Behavior observed in quasi-2D quantum Heisenberg antiferromagnets

Abstract

The magnetic properties of a new family of molecular-based quasi-two dimension $S=1/2$ Heisenberg antiferromagnets are reported. Three compounds, ($Cu(pz{)}_2(Cl{O}_4{)}_2$, $Cu(pz{)}_2(B{F}_4{)}_2$, and $[Cu(pz{)}_2(N{O}_3)](P{F}_6)$) contain similar planes of Cu${}^{2+}$ ions linked into magnetically square lattices by bridging pyrazine molecules (pz = $C_4{H}_4{N}_2$). The anions provide charge balance as well as isolation between the layers. Single crystal measurements of susceptibility and magnetization, as well as muon spin relaxation studies, reveal low ratios of Néel temperatures to exchange strengths ($4.25/17.5=0.243$, $3.80/15.3=0.248$, and $3.05/10.8=0.282$, respectively) while the ratio of the anisotropy fields $H_A$ (kOe) to the saturation field $H_{\mathrm{SAT}}$ (kOe) are small ($2.6/490=5.3\times 10^{-3}$, $2.4/430=5.5\times 10^{-3}$, and $0.07/300=2.3\times 10^{-4}$, respectively), demonstrating close approximations to a 2D Heisenberg model. The susceptibilities of ClO${}_4$ and BF${}_4$ show evidence of an exchange anisotropy crossover (Heisenberg to $XY$) at low temperatures; their ordering transitions are primarily driven by the $XY$ behavior with the ultimate 3D transition appearing parasitically. The PF${}_6$ compound remains Heisenberg-like at all temperatures, with its transition to the Néel state due to the interlayer interactions. Effects of field-induced anisotropy have been observed.

Accepted for publication in Physical Review B

References in corpus (5)

• Magnetic order in the S=1/2 two-dimensional molecular antiferromagnet, copper pyrazine perchlorate Cu(Pz)_2(ClO_4)_2
• Detection of XY behaviour in weakly anisotropic quantum antiferromagnets on the square lattice
• Muon-fluorine entangled states in molecular magnets
• Field-induced XY behavior in the S=1/2 antiferromagnet on the square lattice
• Fermi-Liquid Theory of Non-S-Wave Superconductivity

Cited by in corpus (22)

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• Frustrated two dimensional quantum magnets
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• Quantum effects in a weakly-frustrated S=1/2 two-dimensional Heisenberg antiferromagnet in an applied magnetic field
• Magnetic order in quasi-two-dimensional molecular magnets investigated with muon-spin relaxation
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• Dynamical structure factor of quasi-2D antiferromagnet in high fields
• Control of the third dimension in copper-based square-lattice antiferromagnets
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• Switching of anisotropy and phase diagram of a Heisenberg square lattice S=1/2 antiferromagnet Cu(pz)2(ClO4)2
• Staggered moment dependence on field-tuned quantum fluctuations in 2D frustrated antiferromagnets
• The magnetic ground state of two isostructual polymeric quantum magnets, [Cu(HF${}_2$)(pyrazine)${}_2$]SbF${}_6$ and [Co(HF${}_2$)(pyrazine)${}_2$]SbF${}_6$, investigated with neutron powder diffraction
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• Extremely well isolated 2D spin-$1/2$ antiferromagnetic Heisenberg layers with small exchange coupling in the molecular-based magnet CuPOF
• Magnetic field induced quantum phase transition of the $S=1/2$ antiferromagnet $K_{2}NaCr{O}_8$
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• Low-temperature thermal conductivity and magnetic transitions of the kagomé-staircase compound Ni${}_3$V${}_2$O${}_8$
• Magnetism study on a frustration-free spatially anisotropic $S$ = 1 square lattice antiferromagnet Ni[SC(NH${}_2$)${}_2$]${}_6$Br${}_2$
• Spectral characteristics of the antiferromagnetic spin-1/2 Heisenberg model on the square lattice in a magnetic field
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