NMR evidence for universal nonclassical critical behavior of incommensurately modulated crystals.
Nonclassical universal critical behavior is revealed in several one dimensionally modulated incommensurate (IC) crystals by means or quadrupolar perturbed NMR. In the IC phase the temperature dependence or the NMR line shape leads to the same critical order parameter exponent β for all systems. Above the phase transition a nonclassical exponent was round for the critical contribution to the spin-lattice relaxation. All results agree with the theoretical predictions or the 3D XY model