19F NMR Spin Echo in Antiferromagnetic MnF2

摘要: Spin echoes of 19F NMR have been observed, in zero external field, various samples antiferromagnetic MnF2. The decay the echo envelope was always found to be exponential. This corresponds a Lorentzian line profile, indicating that Gaussian shape previously observed with cw spectrometer and an order magnitude broader, arises from inhomogeneous broadening. A previous calculation indirect nuclear spin‐spin interaction via virtual magnon excitations predicts 3‐μsec T2 envelope. However, (1) destructive interference between dipolar coupling mechanisms (2) appreciable contribution 19F−55Mn much larger 55Mn nuclei fourth moment will reduce relaxation rate, first, by only 20% but second approximately factor eight, change Lorentzian. derived value T2≅30 μsec is agreement wit...