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)2Cd1−xMnxCl4 ( 0 ≤ x ≤ 1 ) by means of 1H 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 1 S ) 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 1 S − 1 thus obtained showed a maximum at a percolation threshold x c ≈ 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.