Pulsed NMRON measurements on insulators

Selective single and double quantum excitation pulsed NMRON has been utilized to obtain rotation patterns, free induction decays, and spin echoes in antiferromagnetic 54Mn-MnCl2.4H2O and the quasi 2-dimensional ferromagnet 54Mn-Mn(COOCH3)2.4H2O. The pulsed technique is well suited to observing fast spin-lattice relaxation and T1 values down to 100 ms have been measured in these systems. These short times may make magnetic insulators viable hosts for on-line experiments. The dependence on field and temperature of the 54Mn spin-lattice relaxation time T1 has been investigated and a T1 minimum at high fields observed in both systems. A spin-spin relaxation time T2≅50 μs is measured in 54Mn-MnCl2.4H2O. The observation of NMRON in the paramagnetic phase of MnCl2.4H2O allows the resonant frequencies in the antiferromagnetic and paramagnetic phases to be compared, yielding a value for the zero point deviation in the former phase. (orig.)