Experiments on adiabatic cooling of paramagnetic salts in magnetic fields

Hyperfine enhanced nuclear magnetic cooling in PrCu$sub 6$

“…The compound PrCug was chosen as a good candidate for a nuclear coolant because of several desirable traits beyond the basic requirements for obtaining hyperfine enhanced cooling: (1) praseodymium nuclei possess a large magnetic moment which means lots of cooling power; (2) the nuclei have a large spin so the spin system entropy is large; (3) the electronic spin angular momentum of praseodymium is small so that exchange interaction induced ordering effects are minimized; (4) its electronic orbital angular momentum is relatively large so that crystal field effects will play a significant part in inhibiting any electronic ordering; (5) the Van Vleck paramagnetic susceptibility is large so the enhancement factor (1*K) was expected to be reasonably high; (6) PrCug is metallic which means its thermal conductivity should be very good and good thermal contact to it by soldering should be possible; and (7) PrCug was metallurgically.realizable with available preparation equipment.…”

Energy Applications of Magnetocaloric Materials

“…The work still represents the basis for the well‐established use of adiabatic demagnetization for sub‐Kelvin and cryogenic cooling. It is noteworthy, however, that there were other researchers who almost simultaneously made important contributions to the field, such as de Hass et al and Kürti and Simon . In 1935, Urbain et al discovered ferromagnetism in gadolinium (Gd), which is the first magnetocaloric material determined to have a Curie temperature close to room temperature.…”

Short time cycles of purely quantum refrigerators

“…Magnetic cooling was initiated more than a half century ago [1]. The cooling agent paramagnetic salts was cooled both by adiabatic demagnetization [1] and by adiabatic magnetization [2] depending on the sign of the isothermal change of entropy as a function of the magnetic field.…”