The Design and Use of Nuclear Orientation Thermometers Employing Mn-54 and Co-60 Nuclei in Ferromagnetic Hosts

The magnetic dipole interaction between the nuclear magnetic moment u and the hyperfine field H-hf in ferromagnetic metals leads to well-defined, evenly spaced nuclear energy levels which are accurately measurable by NMR techniques. When this is combined with the well-established anisotropic gamma-ray emission properties of radioactive nuclei an excellent.basis for absolute temperature measurement between 1 and 30 inK is obtained. Practical applications, however, require consideration of several experimental aspects. These are discussed in detail and graphs and tables are given in such a form that the data can be easily utilized. Experience gained with a nuclear orientation thermometer system employed in a nuclear refrigeration cryostat is discussed. A calibration of a pulsed copper NMR thermometer against a (MnNi)-Mn-54 nuclear orientation thermometer is presented.