Electron-Spin-Resonance Linewidth Variation with Temperature in Some Rare-Earth Salts:T1T2Ratios

We have measured the temperature dependence of the electron-spin-resonance linewidth of Ce, Nd, and Sm in lanthanum magnesium nitrate from below 4°K to as high as 26°K. Both Ce and Nd displayed a linewidth which was essentially Lorentzian at the lowest temperature and which broadened with increasing temperature in accordance with an Orbach relaxation mechanism. A comparison of the strength of this broadening with standard relaxation measurements below 4°K indicated that $\frac{T_1}{T_2}$ was 8.6 for the Nd sample and was estimated to be 13 for the Ce crystal. Sm displayed a temperature-dependent broadening which could be interpreted as due either to a Raman or an Orbach mechanism.