Influence of Paramagnetic Impurities on the Temperature Dependence of Nuclear Magnetic Resonance Lines
The theory of paramagnetic impurity broadening of nuclear magnetic resonance lines in diamagnetic crystals is considered. The concept of a critical radius around each paramagnetic ion, inside which nuclei do not contribute to the observed resonance line, is discussed. It is shown that the inclusion of the temperature dependence of this critical radius gives rise to a T-1 dependence for the contribution to the second moment due to such paramagnetic dipoles. This temperature dependence qualitatively explains experimental low-temperature Li7 linewidth variations in Mn-doped LiF.