William Francis Giauque developed a magnetic refrigeration device

William Francis Giauque – pioneer in thermodynamics

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & contributions

William Francis Giauque was an American chemist and Nobel laureate born on May 12, 1895 – died on March 28, 1982. Giauque is remembered particularly for his discovery of adiabatic demagnetization as a means to reach very low temperatures as well as for his exhaustive and meticulous thermodynamic studies.

Giauque was the receiver of many awards and prizes like Chandler Medal from Columbia University in the year of 1936, Elliott Cresson Medal in the year of 1937, Nobel prize in chemistry in the year of 1949, Willard Gibbs Award in the year of 1951, G. N. Lewis Medal from the American Chemical Society in the year of 1956.

He developed a magnetic refrigeration device. His correlated investigations of the entropy of oxygen with Dr. Herrick L. Johnston, led to the discovery of oxygen isotopes 17 and 18 in the Earth's atmosphere. His findings have led to improvements in the production of substances such as gasoline, glass, rubber, and steel.

Giauque designed and supervised the construction of the heavy equipment for the liquid-fraction of both hydrogen and helium.

Adiabatic demagnetization

Adiabatic demagnetization is the process by which the removal of a magnetic field from certain materials serves to lower their temperature. This procedure, proposed by chemists Peter Debye and William Francis Giauque provides a means for cooling an already cold material to a small fraction of 1 K.

The mechanism involves a material in which some aspect of disorder of its constituent particles exists at 4 K or below. Magnetic dipoles in a crystal of paramagnetic salt have this property of disorder in that the spacing of the energy levels of the magnetic dipoles is small compared with the thermal energy. Under these conditions the dipoles occupy these levels equally, corresponding to being randomly oriented in space.

When a magnetic field is applied, these levels become separated sharply; i.e., the corresponding energies are widely different, with the lowest levels occupied by dipoles most closely aligned with the applied field. If the magnetic field is applied while the paramagnetic salt is in contact with the liquid helium bath many more dipoles will become aligned, with a resultant transfer of thermal energy to the bath. If the magnetic field is decreased after contact with the bath has been removed, no heat can flow back in, and the sample will cool. Such cooling corresponds to the dipoles remaining trapped in the lower energy states. Temperatures from 0.3 K to as low as 0.0015 K can be reached in this way.

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