February 26, 1974 - Death of Hendrika Johanna van Leeuwen, known for her contributions to the theory of magnetism

She had a PhD in Physics from the University of Leiden in the Netherlands, she focused on explaining why magnetism is essentially a quantum mechanical effect (a result now known as the Bohr-van Leeuwen theorem). In this respect, Van Leeuwen was unaware of the results presented 8 years earlier by Niels Bohr also in his doctoral thesis.

Hendrika claimed that if the formulae of classical physics and statistical mechanics are used, the existence of magnetism is not proved and that according to these theories, a system in a magnetic field that is in thermal equilibrium cannot have a net magnetic dipole moment.

In addition to her doctoral research, she also conducted research on the natural vibrations of hydrogen molecules in the same period.

In 1947 she was appointed professor at the Technische Hogeschool in Delft, becoming the first woman professor at this institution.

If you want to know more about this scientist, click on the following link: Hendrika Johanna van Leeuwen