2009 Mott medal and prize
Professor Gillian Gehring
University of Sheffield
For her seminal contributions to magnetism.
Gillian Gehring is distinguished as an international research leader in magnetism. She is unusual in having made important contributions to both theoretical and experimental physics.
Much of her research has been concerned with different phase transitions and her work on cooperative Jahn Teller Effect is very well known. She studied the Random Field model before it had become well known and gave the theory of the phase diagram that took the random fluctuations into account. Linear Birefringence is one of the most accurate methods to study distortions in transparent crystals and Gehring gave the first microscopic theory of this effect, first for Jahn Teller transitions and then more generally for magnetic transitions. Gehring was the first to derive a theory that unified the domains that form in ferromagnetic systems below the phase transition with the critical fluctuations above the phase transition.
Quantum phase transitions are challenging because the ground state must be determined. Gehring provided one of the first demonstrations of the strength of the Density Matrix Renormalisation Group to study quantum phase transitions, being the first to generalise to finite temperature.
At Sheffield, Gehring developed related research on magnetic oxides, which share some of the challenges with Heavy Fermion compounds and founded a group to study the magnetic properties of Fe3O4 and the mixed valent manganites .This has led to the Sheffield’s group pre-eminent position in this field. Most recently, Gehring initiated the study of magnetically doped ZnO and the group produced the first clear evidence of room temperature ferromagnetism in a ZnO sample doped with manganese.