Turkish Journal of Physics

Zn-doped {\rm La_2CuO_4} from ^{139}{\rm La} NQR Relaxation




^{139}La NQR spectra and relaxation rates W are used to study the effects on static magnetic properties (inertial hyperfine field, sublattice magnetization and Neel temperatures T_N) and the spin wave excitations in antiferromagnetic {\rm La_2CuO_4} upon substitution of {\rm Zn^{+2}} (S=0) for {\rm Cu^{+2}} (S=-1/2). The measurements have been carried out in the temperature range 1.6K-350K for Zn doping x up to 0.13. It is found that T_N decreases with x in a way close to the one expected for quasi 2D Heisenberg magnets on square lattice while the sublattice magnetization is only slightly affected by Zn doping. The temperature dependence of the AF field h is close to one in pure {\rm La_2CuO_4} up to x=0.08 with a sudden decrease which can be described in terms of a small critical exponent \beta, while for strong doping a departure from the one in pure {\rm La_2CuO_4} is observed.

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