Felix Bloch (born 23.10.1905) is an American physicist and a member of the National Academy of Sciences (1948). He was born in Zurich. In 1924—27 he studied at the Zurich Polytechnic and graduated from the University of Leipzig (1928). In 1934-77 he worked at Stanford University (professor from 1936), in 1942—45 at the Los Alamos laboratory, and in 1954—55 he was director of CERN.
His research concerned solid-state physics, magnetism, quantum electrodynamics, superconductivity and nuclear physics. Together with L. Brillouin he laid the foundations of the band theory of solids (1928) and of low-temperature ferromagnetism. To describe the motion of electrons in the field of a crystal lattice he proposed a wave function (the Bloch function), which was essential for the understanding of the electronic properties of solids. He introduced spin waves. In 1930 he discovered theoretically the temperature dependence of the spontaneous magnetisation of ferromagnets at temperatures well below the Curie point (Bloch's three-halves power law), and the dependence of the ideal part of the electrical resistivity of metals on temperature (the Bloch — Grüneisen formula). In 1932 he developed a qualitative theory of reversible displacement processes in ferromagnets.
He pointed out (1936) the partial polarisation of neutrons passing through magnetised ferromagnetic material (the Bloch effect) and gave a theory of it. Together with L. Alvarez he measured the magnetic moment of the free neutron in 1940. Independently of E. Purcell he discovered nuclear magnetic resonance in 1946 (Nobel Prize, 1952). He is also known for the Bethe — Bloch formula for stopping power, for Bloch's theorem in the theory of superconductivity, for the Bloch — Nordsieck theorem in quantum electrodynamics, and for the Bloch equations, which describe nuclear magnetic resonance.
In 1965—66 he was president of the American Physical Society.