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  Wolter, A.U.B.; Wzietek, P.; Süllow, S.; Litterst, F.J.; Auban-Senzier, P.; Jérome, D.; Feyerherm, R.; Klauss, H.-H.: ¹³C-NMR under pressure on [PMCu(NO₃)₂(H₂O)₂]_n. Journal of Magnetism and Magnetic Materials 272-276 (2004), p. 1056-1057

10.1016/j.jmmm.2003.12.728

Abstract:
We present an investigation of the S = 1/2 antiferromagnetically coupled Heisenberg spin chain [PMCu(NO3)2(H20)2]n (PM = pyrimidine) with field induced gap Δ by means of 13C-NMR experiments. From these studies carried out as finction of pressure, we determine the NMR shift and the spin-lattice relaxation rate 1/T1 and extract the magnetic exchange parameter J/k_B and the size of the spin gap Δ. The observed pressure response is discussed in comparison to related molecular materials.