Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 72: Poster Session: Correlated Electrons

TT 72.66: Poster

Wednesday, March 14, 2018, 15:00–19:00, Poster B

NMR of the two-dimensional S = 1/2 Heisenberg antiferromagnet CuPOF — •D. Dmytriieva^1,2, Z. T. Zhang¹, M. Uhlarz¹, C. P. Landee³, J. Wosnitza^1,2, and H. Kühne¹ — ¹Hochfeld-Magnetlabor Dresden (HLD-EMFL), HZDR, Dresden, Germany — ²Institut für Festkörper- und Materialphysik, TU Dresden, Germany — ³Department of Physics, Clark University, Worcester, Massachusetts, USA

The metal-organic compound [Cu(pz)₂(2-OHpy)₂](PF₆)₂ (CuPOF) is a molecular-based analog of the two-dimensional quantum S = 1/2 Heisenberg antiferromagnet (2D QHAF) with well-isolated Cu(pz) layers and a very low k_BT_N/J = 0.21 ratio (J/k_B = 6.8 K, T_N = 1.38 K). We present a focus study of the low-temperature phase transition to long-range order performed via ¹H and ³¹P nuclear magnetic resonance (NMR), as well as high-field magnetometry. A low-temperature minimum of the temperature-dependent local and uniform magnetizations at T_min indicates a presence of the magnetic order. Within the ordered state, a splitting of the ¹H NMR spectra reveals commensurate AF order, presumably of checkerboard type. The phase transition, manifested as a sharp maximum of the temperature-dependent ³¹P nuclear spin-lattice relaxation rate 1/T₁, occurs at temperatures slightly lower than T_min, indicating an easy-plane anisotropy as well as a crossover between isotropic and XY behavior.