Six years later he became a university lecturer and in 1978 was appointed a Reader. He also became a fellow of the newly founded
Linacre College, Oxford a graduate college, and subsequently, in 1970, a tutorial fellow of
St Catherine's College, Oxford. Harry Rosenberg's initial research was in the area of metals, but in 1962 new phenomena associated with magnetism and the interaction between
magnetism and
phonons (the quantized vibrations that store and transport heat in insulating as well as metallic solids) began to interest him. This occupied his attention for the next decade. Then, in 1972, he began the work on composite, disordered and amorphous materials that lasted until his retirement. On his 60th birthday, in 1982, Rosenberg was gloomily contemplating the need to find a new topic of research to last until his retirement, when a note from an old colleague,
Ray Orbach in California, showed that his experimental results on the low temperature properties of
amorphous solids found a natural explanation in terms of the newly discovered mathematical theory of
fractals, by now of course familiar through the strange and beautiful pictures that they generate. This new approach to the interpretation of excitations in disordered solids was first expressed in the paper "Fractal interpretation of vibrational properties of cross-linked polymers, glasses and irradiated quartz," which, according to Orbach, was a very controversial piece of work, greeted with considerable skepticism. Rosenberg was regarded as a gifted lecturer, not only to undergraduates and to colleagues at conferences, but also to a much wider audience, both on the radio and on television. ==Death==