Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 6: Niederdimensionale Systeme (incl. Peierls-Übergang, organische Leiter, ...)

TT 6.11: Vortrag

Montag, 8. März 2004, 16:45–17:00, H18

³¹P NMR in the S=1/2 one–dimensional chain Sr₂Cu(PO₄)₂ — •A. Mahajan¹, R. Nath¹, Ch. Kegler¹, N. Büttgen¹, A. Loidl¹, J. Bobroff², and H. Alloul² — ¹Experimentalphysik V, EKM, Institut für Physik, Universität Augsburg — ²Laboratoire de Physique des Solides, Orsay, France

We present ³¹P NMR and bulk susceptibility χ measurements on a new S = 1/2 Heisenberg antiferromagnetic (HAF) chain compound Sr₂Cu(PO₄)₂. The susceptibility χ(T) is found to vary according to the Bonner-Fisher formalism expected for S = 1/2 one–dimensional (1D) HAF chains [1]. The intra-chain exchange interaction between the nearest–neighbour Cu spins is found to be J/k_B = 150 K. The ³¹P NMR shift K(T) is proportional to χ(T) and no magnetic long–range order is found down to 1.5 K. The decay of the transverse magnetisation following a π/2−τ−π pulse sequence is found to be Gaussian as in other 2D and 1D S = 1/2 HAF systems [2]. The spin–spin relaxation rate 1/T₂ is temperature independent while the spin–lattice relaxation rate 1/T₁ varies linearly with T between 10 K and 250 K. These two results suggest a dominant contribution to the relaxation from fluctuations of the uniform susceptibility rather than the staggered susceptibility in this temperature range [3].

[1] J. C. Bonner and M. E. Fisher, Phys. Rev. 135, A640 (1964)

[2] C.H. Pennington and C.P. Slichter, Phys. Rev. Lett. 66, 381 (1991); M. Takigawa et al., Phys. Rev. Lett. 76, 4612 (1996)

[3] S. Sachdev, Phys. Rev. B 50, 13006 (1994)