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

Abstract

We report on a comprehensive characterization of the newly synthesized Cu 2+-based molecular magnet [Cu(pz) 2 (2-HOpy) 2 ](PF 6) 2 (CuPOF), where pz = C 4 H 4 N 2 and 2-HOpy = C 5 H 4 NHO. From a comparison of theoretical modeling to results of bulk magnetometry, specific heat, μ + SR, ESR, and NMR spectroscopy, this material is determined as an excellent realization of the two dimensional square-lattice S = 1 2 antiferromagnetic Heisenberg model with a moderate intraplane nearest-neighbor exchange coupling of J/k B = 6.80(5) K, and an extremely small interlayer interaction of about 1 mK. At zero field, the bulk magnetometry reveals a temperature-driven crossover of spin correlations from isotropic to XY type, caused by the presence of a weak intrinsic easy-plane anisotropy. A transition to long-range order, driven by the low-temperature XY anisotropy under the influence of the interlayer coupling, occurs at T N = 1.38(2) K, as revealed by μ + SR. In applied magnetic fields, our 1 H-NMR data reveal a strong increase of the magnetic anisotropy, manifested by a pronounced enhancement of the transition temperature to commensurate long-range order at T N = 2.8 K and 7 T.

Tight-Binding Approach to Pyrazine-Mediated Superexchange in Copper–Pyrazine Antiferromagnets

“…The exchange interactions in structurally homologous, chemically similar materials can often vary widely, , offering an opportunity to design and investigate materials by finely tuning their geometries. Although an abundance of experimental information is available for these materials, ,− the factors that control the magnetic interactions are still debated. To be able to design materials with specific sets of magnetic interactions, these factors need to be understood in great detail.…”

Signatures for Berezinskii-Kosterlitz-Thouless critical behavior in the planar antiferromagnet BaNi2V2O8

“…BKT phenomena were experimentally observed in ideal physical realizations of the 2D XY model such as superfluids [6], superconducting thin films [7], 2D organic magnetic complexes [8,9], and more recently in a triangular lattice quantum Ising system [10]. Signatures for BKT behavior were also reported in promising solid-state prototypes of the 2D XY model among layered magnets such as K 2 CuF 4 , Rb 2 CrCl 4 , BaNi 2 X 2 O 8 (X = As, P), and MnPS 3 [11][12][13][14][15][16].…”

Hierarchical single-ion anisotropies in spin-1 Heisenberg antiferromagnets on the honeycomb lattice

“…In recent years, the search for solid-state realizations of Berezinskii-Kosterlitz-Thouless (BKT) topological phase transitions [1][2][3] in magnetic compounds has lead to the identification of several quasi two-dimensional (2D) antiferromagnetic candidate materials [4][5][6]. While in most systems, the BKT behavior is obstructed by the presence of residual interlayer couplings, these were found to be negligible for the specific Ni 2+ based compound BaNi 2 V 2 O 8 , in which spin-1 degrees of freedom reside in effectively decoupled 2D honeycomb lattice layers [7,8].…”