Nuclear Spin-Lattice Relaxation in Metals

Abstract

The nuclear spin-lattice relaxation time, $T_1$, has been measured in the range of 1.1°K to 4.2°K for the metals lithium, sodium, aluminum, and copper. A combination of nuclear magnetic resonance at fixed frequency and adiabatic variation of the magnetic field was used to measure $T_1$ as a function of field between zero and one thousand gauss. At fields of between one hundred and one thousand gauss $T_1$ is independent of magnetic field and inversely proportional to temperature in agreement with theory. The experimental values of the relaxation time multiplied by absolute temperature in sec °K are 44±2.0 for ${\mathrm{Li}}^7$; 5.1±0.3 for ${\mathrm{Na}}^{23}$; 1.80±0.05 for ${\mathrm{Al}}^{27}$; 1.27±0.07 for ${\mathrm{Cu}}^{63}$. These values are in good agreement with previous experimental data at room temperature and above. At fields comparable with the nuclear magnetic dipole-dipole fields, $T_1$ is a function of applied field. The theory of relaxation in low fields is presented in an elementary form. Qualitative agreement with theory is obtained for ${\mathrm{Al}}^{27}$ and ${\mathrm{Cu}}^{63}$; detailed agreement is obtained for ${\mathrm{Li}}^7$ and ${\mathrm{Na}}^{23}$.