The English scientist William Gilbert (1544–1603) regarded Earth as a giant magnet and investigated its magnetic field in terms of dip and variation. He explored many other magnetic and electrostatic phenomena. The Gilbert (Gb), a unit of magnetism, is named for him.

John H. Van Vleck (1899–1980), an American physicist, made significant contributions to modern magnetic theory. He explained the magnetic, electrical, and optical properties of many elements and compounds with the ligand field theory, demonstrated the effect of temperature on paramagnetic materials (called Van Vleck paramagnetism), and developed a theory on the magnetic properties of atoms and their components.