William Fuller Brown Jr. (21 October 1904 – 1983) was an American physicist who developed the theory of micromagnetics, a continuum theory of ferromagnetism that has had numerous applications in physics and engineering. He published three books: Magnetostatic Principles in Ferromagnetism, Micromagnetics, and Magnetoelastic Interactions. Biography William Fuller Brown Jr. was born in Lyon Mountain, New York on September 21, 1904 to William Fuller Brown and Marie E. Williams. An early interest in electromagnetism was stimulated by a toy motor but "destimulated" by high school and college physics courses. He graduated from Cornell University with a BA in English in 1925 and began teaching at Carolina Academy, a private high school in Raleigh, North Carolina. This "restimulated" his interest in physics. In 1927, Brown enrolled in Columbia University. With S. L. Quimby as his doctoral advisor, he wrote a dissertation on the effect of magnetization on the elastic properties of iron. On August 17, 1936 he was married to Shannon Johnson. He received his PhD in physics in 1937. In 1938 Brown was appointed assistant professor of physics at Princeton University. It was during this period that he developed micromagnetics. In 1941, he went to the U.S. Naval Ordnance Laboratory, where he headed a team that was working on methods to protect ships against magnetic mines. He developed novel methods for degaussing ships and instrumentation for measuring magnetic fields and the magnetic properties of steels. For his work he was awarded the Meritorious Civilian Service Award by the U.S. Navy. From 1946 to 1955, Brown worked in Newton Square, Pennsylvania as a research physicist at the Sun Oil Company, investigating dielectric and ferromagnetic phenomena. In 1955 he moved to Minnesota and worked with the 3M Company as a senior research physicist, where there was a strong interest in ferromagnetic single-domain particles. In 1957 Brown became a professor of electrical engineering at the University of Minnesota. He remained in this position until he became emeritus in 1973, aside from 1962 (when he was a Fulbright scholar at the Weizmann Institute in Rehovot, Israel) and 1963–1964 (when he was guest professor at the Max Planck Institute for Metals Research in Stuttgart). He died in St. Paul, Minnesota in 1983. Development of micromagnetics At the time of Brown's graduation from Cornell, the theory for magnetic domains was not very developed. Richard Becker and Werner Döring, in their book Ferromagnetismus, emphasized internal stresses. Brown