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Van Vleck, John (Hasbrouck)

magnetic theory properties radar

(1899–1980) US physicist: a major contributor to modern theories of magnetic systems.

Van Vleck’s father and grandfather were both eminent mathematicians. Van Vleck emerged from study at Wisconsin and Harvard to take up a post at Minnesota in 1923. He later returned to chairs at Wisconsin and Harvard.

Van Vleck largely founded the modern theory of magnetism, taking quantum mechanics and working out the implications for the magnetic properties of atoms. In 1932 he published The Theory of Electric and Magnetic Susceptibilities , which laid out the theory and which remains in use today as a classic text. In it the paramagnetic properties of atoms are discussed; the temperature-independent susceptibility is now called Van Vleck paramagnetism.

He also studied chemical bonding in crystals and developed the crystal field and ligand field theories. These allow one to predict and explain some features of magnetic, electrical and spectroscopic properties of metal compounds. Furthermore, Van Vleck explained how local magnetic moment formation is assisted by electron correlation (the interaction between the motion of electrons). His wartime work resulted in showing how water and oxygen in the atmosphere give rise to absorption of radar signals, and was important in devising useful radar systems.

Van Vleck has been described as ‘one of the few true gentlemen and scholars’; he was a quiet man with charm. In 1977 his pioneering research was recognized with a joint award of the Nobel Prize for physics.

Vanderbilt, Cornelius - Overview, Personal Life, Career Details, Chronology: Cornelius Vanderbilt, Social and Economic Impact [next] [back] Van Surly DeGrasse, John(1825–?) - Physician, surgeon, Admitted to Massachusetts Medical Society, Chronology

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