Angular dependence of the spin-packet width in dilute ruby samples

Abstract

The spin-packet width Delta h of the inhomogeneous resonance lines of dilute ruby samples (Cr2O3:Al2O3) has been measured as a function of the orientation of the external field H0 with respect to the crystal c axis. The results show that the broadening of the packet lines arising from the fluctuations of the superhyperfine interaction occurs within a few degrees around the parallel orientation. Moreover, this broadening mechanism is shown to be peculiar to the low-field lines of very dilute samples, since no angular dependence of Delta h was detected either in high magnetic fields or in concentrated samples. The relationship between the reported results and the results of spin-echo, photon-echo and stirring effect experiments is examined and the lack of a rigorous theory is pointed out. The authors also discuss some advantages of the method used here for measuring Delta h with respect to the traditional ones.