Nuclear Magnetic Resonance in LiquidHe3

The nuclear magnetic susceptibility $\chi$ of liquid ${\mathrm{He}}^3$ has been studied as a function of temperature (0.07 to 4.2°K) and pressure (0.7 to 27.5 atm). it has been found that Curie's law holds above 2°K, where the experimental results showed an rms deviation of less than 1.5%. At 1.1°K the liquid is (5±1.5)% degenerate; no pressure dependence of $\chi$ could be detected above 1.2°K. As the temperature is reduced below 1.1°K, the product ${\chi }^T$ falls monotonically and $\chi$ tends towards the constant zero-temperature limiting value; $\chi$ increases with increasing pressure in this temperature range and values of $T_F^{}{}_{}{}^{**}$, the magnetic degeneracy temperature, as a function of pressure are given. The low-temperature results are considered in the light of the Fermi-liquid theory of Landau and its extension to finite temperatures. A plot of reduced susceptibility versus reduced temperature, of the type suggested by Goldstein, indicates that data at all pressures and temperatures may be described closely (within 3%) by a single function. Comparison of this work is made with published results from other laboratories. The spin-lattice relaxation time has also been investigated over the same pressure and temperature ranges, and lower limits for ${\left(T_1\right)}_{\mathrm{bulk}}$ at low temperatures have been deduced. An analysis of the type suggested by Low and Rorschach was applied for this purpose. The results are the first reported in the Fermi-liquid region, and at higher temperatures they are compared with data published elsewhere. Low-temperature thermometry was facilitated by measurement of the nuclear susceptibility of ${\mathrm{F}}^{19}$ in a calcium fluoride crystal immersed in the liquid ${\mathrm{He}}^3$.