Rosenfeld obtained a PhD at the University of Liège in 1926, and he was a close collaborator of the physicist Niels Bohr from 1930 until Bohr's death in 1962. Rosenfeld published in 1930 the first systematic Hamiltonian approach to Lagrangian models that possess a local gauge symmetry, which predates by two decades the work by Paul Dirac and Peter Bergmann. Rosenfeld contributed to a wide range of physics fields, from statistical physics and quantum field theory to astrophysics. Along with Frederik Belinfante, he derived the Belinfante–Rosenfeld stress–energy tensor. He also founded the journal Nuclear Physics and coined the term lepton.