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 Leiden University (abbreviated as ''LEI''; nl, Universiteit Leiden) is a public research university in Leiden, Netherlands. The university was founded as a Protestant university in 1575 by William, Prince of Orange, as a reward to the city of L ...

under the guidance of

Hendrik Antoon Lorentz Hendrik Antoon Lorentz (; 18 July 1853 – 4 February 1928) was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect. He also derived the Lorentz t ...

, obtaining her doctorate in 1919. Her thesis explained why

magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

is an essentially quantum mechanical effect, a result now referred to as the Bohr–van Leeuwen theorem. (

Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. B ...

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 Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...

), first as "assistant" between September 1920 and April 1947, and then she was promoted to "

lector Lector is Latin for one who reads, whether aloud or not. In modern languages it takes various forms, as either a development or a loan, such as french: lecteur, en, lector, pl, lektor and russian: лектор. It has various specialized uses. ...

in de theoretische en toegepaste natuurkunde" (reader in theoretical and applied physics). Hendrika van Leeuwen was the sister-in-law of

Gunnar Nordström Gunnar Nordström (12 March 1881 – 24 December 1923) was a Finnish theoretical physicist best remembered for his theory of gravitation, which was an early competitor of general relativity. Nordström is often designated by modern writers as ...

, known as the "Einstein of Finland", who studied in Leiden with

Paul Ehrenfest Paul Ehrenfest (18 January 1880 – 25 September 1933) was an Austrian theoretical physicist, who made major contributions to the field of statistical mechanics and its relations with quantum mechanics, including the theory of phase transition an ...

, the successor of Lorentz. Her sister Cornelia (Nel) also started a PhD in Leiden, under Willem Keesom, but stopped when she married Nordström and moved with him to Helsinki. Van Leeuwen was present at the celebration of the golden anniversary of the doctorate of Lorentz, on 11 December 1925, and on that occasion reported on the role of Lorentz as scientist and teacher. The English translation of the Dutch text reads: ''For us, his pupils, Lorentz was not only the great scientist, but also an example to follow as a friendly, upbeat person with a great sense of duty, admirable simplicity and warm interest for all around him. Many a great physicist enjoyed being one of Lorentz's students for a shorter or longer period of time. There is no better way to honor our great teacher, than to attempt to continue our own work with all our strengths, enthusiasm and care.''

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