Pierre Weiss

Pierre-Ernest Weiss (25 March 1865 – 24 October 1940) was a French physicist who specialized in magnetism. He developed the domain theory of ferromagnetism in 1907. Weiss domains and the Weiss magneton are named after him. Weiss also developed the molecular or mean field theory, which is often called Weiss-mean-field theory, that led to the discovery of the Curie–Weiss law. Alongside Auguste Piccard, Pierre Weiss is considered one of the first discoverers of the magnetocaloric effect in 1917.

Pierre Weiss made several experimental discoveries that led to the development of the strongest electromagnets of the beginning of the 20th century. He worked at the universities of Rennes, Lyon, ETH Zurich where he was raised, and finally at Strasbourg. In these academic institutions he founded several renown laboratories.

During his lifetime, Weiss was nominated 23 times for the Nobel Prize in Physics.

Life

Early life and education Pierre Weiss was born in Mulhouse the 25 March 1865, where he was the first born of Émile Weiss and Ida Schlumberger. At the age of 5, Alsace was annexed to Germany. Weiss conducted his secondary studies at Mulhouse. He later left to continue higher education at the Swiss Federal Institute of Technology in Zurich (ETH), where he obtained the diploma of mechanical engineer in 1887 as the first in the grade ranking of his class. At the age of majority, he decided to take the French nationality instead of the German one. In 1888, he practiced for the entry exam of the École Normale Supérieure (ENS) at the Lycée Saint-Louis, Paris, where he was admitted. After his years at the ENS, he remained there as a teacher assistant while in parallel he obtained his license in physical sciences and mathematical sciences at the Faculty of Sciences of Paris. During his time in Paris, he met several colleagues who will become famous mathematicians like Élie Cartan, Henri Lebesgue, and Émile Borel, and famous physicists like Aimé Cotton, Jean Perrin, and Paul Langevin. and the thesis jury comprised Charles Friedel, and Henry Pellatt. Pierre Weiss joined the academics that defended Alfred Dreyfus, who was also of Alsace origin (born in Mulhouse) and another former ETH student. This position was controversial during his time at Rennes, so Weiss later preferred to teach at the University of Lyon in 1899 due to this issue. Their daughter, Nicole, later married the French mathematician Henri Cartan.

As a widower in 1919, Pierre Weiss remarried in 1922 to physicist Marthe Klein.

Important works Sur le diamagnétisme des ions Sur l'interpretation énergétique du champ moléculaire et l'aimantation paramagnétique G. Foëx & P. Weiss (1926), Le magnétisme, Armand Colin, Section Physique N°71.