Spin-spin relaxation of 153Eu in ferromagnetic EuO

Abstract

The nuclear spin-spin relaxation time, T 2, of 153Eu in EuO has been investigated at 4 K. In zero external field, the spectrum consists of a narrow line of 100 kHz half-width superimposed with a 10 MHz broad background. The narrow line is shown to arise from the nuclei in the domain walls, whereas the broad background is attributed to the nuclei in the domains. For a spherical single crystal, a narrow line with nearly the same width of the wall signal is observed also in the magnetically saturated state. However, the relaxation characteristics of these lines are completely different. For the saturated state the relaxation is found to be uniform across the whole line. For the wall signal, however, the relaxation is frequency dependent, the maximum rate occuring at the center of the line. This is explained in terms of the Suhl-Nakamura interaction by taking into account a long range of interaction for the nuclei in the walls, instead of a short range for those in the domains.