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Giauque, William Francis

temperature magnetic low temperatures

[jee ohk ] (1895–1982) US physical chemist: pioneer of low temperature techniques.

Giauque hoped to become an electrical engineer when he left school at Niagara Falls, but he failed to find a job in a power plant and for 2 years worked in a laboratory at a chemical plant, which moved his interest to chemistry. This became his main study at the University of California at Berkeley, where he subsequently remained for all his professional life.

In 1925 he proposed a method known as adiabatic demagnetization for achieving temperatures below 1 K, which had hitherto been unattainable. The method consists of placing a sample of a paramagnetic substance, at as low temperature as possible, in a very strong magnetic field; this causes the elementary magnetic ions in the substance to become aligned. When the magnetic field is switched off the elementary magnetic ions tend to increase their entropy by becoming randomly aligned, but since this requires energy the temperature of the sample will drop. Despite considerable practical difficulties, Giauque himself achieved a temperature of 0.1 K by this technique in 1933, and soon afterwards temperatures of a few thousands of a kelvin had been reached. The method remains the basis for reaching very low temperatures today. Giauque was awarded the Nobel Prize for chemistry in 1949 for his discovery. He was also the first to discover, in 1929, that atmospheric oxygen contains the isotopes oxygen-17 and oxygen-18

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