Polarization ofMn55Nuclei: Cryogenic Aspects

A brief discussion of certain cryogenic aspects of nuclear polarization is given. This discussion is applied to ${\mathrm{Mn}}^{55}$ in the paramagnetic salt Mn${\left(\mathrm{N}{\mathrm{D}}_4\right)}_2$ ${\left(\mathrm{S}{\mathrm{O}}_4\right)}_2$·6${\mathrm{D}}_2$O. Measurements on this salt of the temperature in the range $0.12°\le T\le 0.35°$K and of magnetic moment up to 90 percent of saturation as a function of magnetic field in the range $660\le H\le 4560$ gauss and for an entropy $\frac{S}{R}=0.514\mathrm{}$ are described. These measurements are used to calculate the nuclear polarization as a function of field in this magnetic field range and at this entropy, and they form the cryogenic basis for ${\mathrm{Mn}}^{55}$ polarization experiments reported previously.