Nuclear magnetic relaxation in the quasi-two-dimensional (C2H5NH3)2Cd1-xMnxCl4 mixed crystal systems

We have studied the quasi-two-dimensional layered compound systems (C2H5NH3)(2)Cd1-xMnxCL4 (0 <= x <= 1) by means of H-1 nuclear magnetic resonance (NMR) measurements. In contrast to the case of the unmixed crystal compounds (x=0, 1) following a single-exponential type of the NMR spin-lattice relaxation, a stretched-exponential type of recovery, M(t) = M-0[1 - exp( - t/T-1S)(n)], was necessary for the stoichiometric composition systems in addition to it, the exponent n depending on the randomly distributed paramagnetic Mn impurity concentration x. The spin-lattice relaxation rate T-1s(-1) thus obtained showed a maximum at a percolation threshold x(c) approximate to 0.3, in agreement with a percolation theory of the paramagnetic impurity relaxation. The stacking dimensions of the paramagnetic ions were derived from the exponent n as a function of x. (C) 2013 Elsevier Ltd. All rights reserved.