Stoner, Edmund Clifton (1899–1968), physicist, was born on 2 October 1899 at East Molesey, Surrey, the only child of Arthur David Hallett Stoner (1870–1938), cricket professional, and his wife, Mary Ann (1868–1955), a domestic servant, daughter of Thomas Robert Fleet, of Streatham, London. He was educated at Bolton grammar school and at Emmanuel College, Cambridge, where he was awarded an open exhibition in natural sciences. He obtained a first class in both part one (1920) and part two (physics, 1921) of the natural sciences tripos. In 1921 he was awarded a Department of Scientific and Industrial Research maintenance grant to carry out research work at the Cavendish Laboratory under the supervision of Sir E. Rutherford. His first paper (1922), with Gilbert Stead, concerned low voltage glows in mercury vapour; a slightly later paper, with L. H. Martin, concerned the absorption of X-rays. The interest engendered by this and related problems of atomic structure led directly to some of Stoner‘s greatest work in theoretical physics.

In 1924 Rutherford supported Stoner’s successful application for a lectureship in physics at the University of Leeds. Thereafter he was promoted to a readership in physics in 1927 and to the professorship of theoretical physics in 1939. In 1928 Emmanuel College awarded him a research fellowship, which he retained until 1931. He followed R. Whiddington as Cavendish professor of physics at Leeds in 1951. In the same year he married (Jean) Heather, daughter of Herbert Crawford. They had no children. Stoner took his administrative duties so seriously that his last scientific publication is dated 1954. In 1963 he retired, slightly early, from the chair.

Stoner‘s greatest contributions to theoretical physics came both very early and near the end of his scientific career (which was interrupted by war work just when his scientific creativity was at a high point). His early work on X-ray absorption awoke his interest in the distribution of electrons among atomic energy levels. This led to the first publication, in 1924, of the result, which turned out to be correct, that the total number of electrons required to complete a group of quantum number n is 2n2. The scheme corresponded to a maximum of one electron in each possible and equally probable state. Pauli, who came across Stoner’s paper by chance, stated this scheme more axiomatically in 1925 and it soon became known as the exclusion principle, earning Pauli the Nobel prize. Stoner had pointed out that some evidence for this distribution of electrons came from the magnetic moments of the ions of the elements of the first transition series. Thus was laid the basis for Stoner‘s abiding interest in the magnetism of matter.

A number of other influences shaped Stoner’s later research, namely a love of numerical calculations, a realization of the importance of thermodynamics, and a strong feeling that theoretical and experimental physics must be closely interrelated. Thus he published in 1938 and 1939 two seminal papers on the theory of the magnetic properties of metallic ferromagnets, such as nickel. This theory was called by Stoner the collective electron treatment. Its influence took several decades until the 1960s to become widespread throughout the mainstream of the physics of solids. The concepts called Stoner model, Stoner excitations, Stoner criterion for ferromagnetism, and Stoner parameter became widely used in discussing the ferromagnetism of metals and alloys. A decade after Stoner‘s death many scientists felt that, had he been alive, he would have been a strong candidate for the Nobel prize. Stoner collaborated in two other important pieces of research. In a joint publication of 1949 a thermodynamic treatment was given of the heat changes during magnetic hysteresis cycles. In 1948 another joint publication laid the basis of the later theory of permanent magnets, magnetic recording tapes, and magnetic thin films.

In 1937 Stoner was elected FRS and in 1938 the University of Cambridge awarded him the degree of ScD. He delivered the Kelvin lecture of the Institution of Electrical Engineers in 1944 and the Physical Society Guthrie lecture in 1955, the respective titles being ‘Magnetism in theory and practice’ and ‘Magnetism in retrospect and prospect’.

Stoner was modest and kind. For most of his life he was in poor health, partly due to diabetes, which became evident from 1919, but he nevertheless enjoyed photography, gardening, and piano playing. His apparent frailness was often deceptive and hidden strength allowed him to pursue his chosen aims. The greatest personal influences in his life were his mother, for whom he cared until her death at the age of eighty-seven, in 1955, and his wife, who survived him. He died in Leeds on 27 December 1968.

5. E.P. Wohlfarth, rev. Isobel Falconer  (from the Oxford Dictionary of National Biography)