Wander Johannes de Haas and Albert Einstein investigated mechanical motion produced by changing the magnetization of a suspended body. Magnetic reversal changes microscopic angular momentum; a compensating rotation of the body tests angular-momentum conservation. Their experiment connected an apparently internal magnetic property with a visible mechanical response. Interpreting a gyromagnetic measurement requires the relation between magnetic moment and angular momentum, rather than treating magnetization as a force acting independently of its microscopic carriers.[ref]
Experimental proof of the existence of Ampère's molecular currents by Albert Einstein and Wander Johannes de Haas. 1915 report, magnetic reversal and mechanical rotation experiment
A physicist who researched magnetism and became a professor at Leiden in 1924.[ref]
Wander Johannes de Haas, 1878–1960 by H. B. G. Casimir. Career paragraphs: PTR research staff 1913–1915; Delft, Groningen and Leiden professorships
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Portrait of Wander Johannes de Haas
. Unknown photographer; Huygens Laboratorium, Universiteit Leiden; reproduced in Dirk van Delft, Heike Kamerlingh Onnes: Een biografie (2005), p. 529. Public domain (author life plus 70 years; published before 1931). Source usage terms, via Wikimedia Commons. Source. Articles by others on the same topic
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Wander Johannes de Haas was a Dutch physicist known for his contributions to the field of magnetism and the study of magnetic phenomena. He is particularly recognized for his work on the properties of magnetic materials and the development of various experimental techniques in physics. De Haas is perhaps best known for the "de Haas-van Alphen effect," which describes the oscillatory behavior of magnetization in a material as a function of an applied magnetic field.