Hendrika Johanna van Leeuwen

In this article, Dutch capitalization is used for tussenvoegsels in Dutch family names. The first letter in Van Leeuwen is capitalized unless it is preceded by a name, initial or title of nobility.

Hendrika Johanna van Leeuwen (July 3, 1887 – February 26, 1974) was a Dutch physicist known for her early contributions to the theory of magnetism. She studied at Leiden University under the guidance of Hendrik Antoon Lorentz, obtaining her doctorate in 1919. Her thesis ^[1][2] explained why magnetism is an essentially quantum mechanical effect,^[3] a result now referred to as the Bohr–Van Leeuwen theorem. (Niels Bohr had arrived at the same conclusion a few years earlier.) She continued to investigate magnetic materials at the "Technische Hogeschool Delft" (now called the Delft University of Technology), first as "assistant" between September 1920 and April 1947, and then she was promoted to "lector in de theoretische en toegepaste natuurkunde" (reader in theoretical and applied physics).^[4][5]

Hendrika Johanna van Leeuwen
Van Leeuwen about 1920
Born	(1887-07-03)July 3, 1887 The Hague
Died	February 26, 1974(1974-02-26) (aged 87) Delft
Alma mater	Leiden University
Known for	Bohr-van Leeuwen theorem
Spouse	none
Scientific career
Fields	Physicist
Institutions	Delft University of Technology
Thesis	Vraagstukken uit de electronentheorie van het magnetisme (1919)
Doctoral advisor	Hendrik Antoon Lorentz

Hendrika van Leeuwen was the sister-in-law of Gunnar Nordström, known as the "Einstein of Finland", who studied in Leiden with Paul Ehrenfest, the successor of Lorentz. Her sister Cornelia (Nel) also started a PhD in Leiden, under Willem Hendrik Keesom, but stopped when she married Nordström and moved with him to Helsinki.^[5]

Van Leeuwen was present at the celebration of the golden anniversary of the doctorate of Lorentz, on 11 December 1925,^[6] and on that occasion reported on the role of Lorentz as scientist and teacher.^[7]