Extremely well isolated two-dimensional spin-1/2 antiferromagnetic Heisenberg layers with a small exchange coupling in the molecular-based magnet CuPOF

Opherden, D.; Nizar, N.; Richardson, K.; Monroe, J.C.; Turnbull, M.M.; Polson, M.; Vela, S.; Blackmore, W.J.A.; Goddard, P.A.; Singleton, J.; Choi, E.S.; Xia, F.; Williams, R.C.; Lancaster, T.; Pratt, F.L.; Blundell, S.J.; Skourski, Y.; Uhlarz, M.; Ponomaryov, A.N.; Zvyagin, S.A.; Wosnitza, J.; Baenitz, M.; Heinmaa, I.; Stern, R.; Kühne, H.; Landee, C.P.

doi:https://doi.org/10.34657/5655

Extremely well isolated two-dimensional spin-1/2 antiferromagnetic Heisenberg layers with a small exchange coupling in the molecular-based magnet CuPOF

Date

2020

Authors

Opherden, D.

Nizar, N.

Richardson, K.

Monroe, J.C.

Turnbull, M.M.

Polson, M.

Vela, S.

Blackmore, W.J.A.

Goddard, P.A.

Singleton, J.

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Volume

102

Issue

6

Journal

Physical review : B : covering condensed matter and materials physics

Publisher

Woodbury, NY : Inst.

Link to publishers version

https://doi.org/10.1103/PhysRevB.102.064431

Abstract

We report on a comprehensive characterization of the newly synthesized Cu2+-based molecular magnet Cu(pz)2(2-HOpy)22 (CuPOF), where pz=C4H4N2 and 2-HOpy=C5H4NHO. 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=12 antiferromagnetic Heisenberg model with a moderate intraplane nearest-neighbor exchange coupling of J/kB=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 TN=1.38(2) K, as revealed by μ+SR. In applied magnetic fields, our H1-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 TN=2.8 K and 7 T. © 2020 authors.