After getting his degree, De Haas worked in Berlin as a researcher at the
Physikalische Reichsanstalt. Then he returned to the Netherlands, worked as a schoolteacher in
Deventer, a conservator of the
Teylers Museum in
Haarlem, and then a physics professor in
Delft Technical School and
University of Groningen. In 1925, he became a professor in Leiden, and one of the two heads of the Laboratory of physics, succeeding Kamerlingh Onnes. In 1948, De Haas retired. An example of the equipment (an electromagnet of c.1930) used for his low-temperature research can be seen in the
Boerhaave Museum, the history of science museum in Leiden. In 1922 he became member of the
Royal Netherlands Academy of Arts and Sciences. Twenty years later, in 1942, he was forced to resign. After World War II ended in 1945, he was allowed to rejoin as a member. ==References==