Emeritus Professor Gillian Gehring

Department of Physics and Astronomy
Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK
Tel(direct): +44 (0)114 2224299

email : g.gehring@sheffield.ac.uk

Introduction

For many applications the approximation that electrons move in a solid independently of each other and the movement of the ion cores is surprisingly good. Really interesting phenomena occur when this approximation breaks down: this includes magnetism, orbital ordering and superconductivity.
My work is concerned with magnetism and orbital ordering.
Some semiconductors can become ferromagnetic when they are doped with magnetic ions. We study ZnO using transport and magneto-optics. My theoretical work is concerned with understanding these phenomena. The experimental work is given in the associated site (link to follow).
Another interest is in the way in which sound waves scatter from objects to give a pleasing effect in a concert hall. This is done in collaboration with Professor Whittaker in Sheffield and a group led by Professor Angus at Salford.
Since I retired I became an Emeritus Professor and hold a Leverhulme Emeritus Fellowship and am devoting almost all my time to research.

Recent theoretical papers include:

• Volume collapse in LaMnO₃ studied using an anisotropic Potts model. M R Ahmed and G A Gehring, Phys Rev B 79, 174106 (2009)
• Theory of magnetism with temporal disorder applied to magnetically doped ZnO. G A Gehring, M R Ahmed and A J Crombie J. Appl Phys 105, 07E325 (2009)
• Pressure Induced Quantum Phase Transitions. G A Gehring, Euro Phys Lett 82, 60004 (2008)
• Monte Carlo simulation of growth of binary bcc structured layers. Rui-Qiang Zhang, Xiao-Hong Xu, Shun-Yan Zhang and G A Gehring, Phys Rev B78, 075419 (2008)
• The spin Frank-Condon effect. Ahmed M R, Gehring G A. J Phys Cond Matt 19 Art. No. 256208 (2007)
• Magnetic order and valency at La_0.7Sr_0.3MnO₃/SrTiO₃ interfaces. Zenia H, Gehring G A, Temmerman W M. New Journal of Physics 9 : Art. No. 105 (2007)
• A study of the optimization of parameters for pulsed laser deposition using Monte Carlo simulation. X H Xu, R Q Zhang, X Z Dong and G A Gehring. Thin solid films 515, 2754 (2006)
• Potts model for the distortion transition in LaMnO₃. M R Ahmed and G A Gehring. Physical Review B 74 014420 (2006)
• The phase diagram of an anisotropic Potts model. M R Ahmed and G A Gehring. J Phys A-Math Gen 38, 4047-4067 (2005)
• Ab initio charge, spin and orbital energy scales in LaMnO₃. R Tyer, W M Temmerman, Z Szotek, G Banach, A Svane, L Petit L and G A Gehring. Europhys Lett 65 519-525 (2004)

Recent experimental publications include:

• X-ray absorption fine structure and magnetization characterization of the metallic Co component in Co-doped ZnO thin films SM Heald, T Kaspar, T Droubay, V Shutthanandan, S Chambers, A Mokhtari, A J Behan, H J Blythe, J R Neal, A M Fox and G A Gehring, Phys Rev B 79 075202 (2009)
• Magnetic and transport properties of n-type Fe-doped In₂O₃ ferromagnetic thin films. X H Xu, F X Jiang, J Zhang, X C Fan, H S Wu and G A Gehring, Appl Phys Lett 94, 212510 (2009)
• Magnetic circular dichroism spectroscopy in epitaxial La_0.7Sr_0.3MnO₃ thin films. T K Nath, J R Neal and G A Gehring, J. Appl Phys 105, 07D709 (2009)
• Magnetoresistance of magnetically doped ZnO films A J Behan, A Mokhtari, H J Blythe, M Ziese, A M Fox and G A Gehring, J Phys Cond Matt 21, 346001 (2009)
• Enhancement of magnetic moment of Co-doped ZnO films by postannealing in vacuum. X L Li, Z L Wang, X F Qin, H S Wu, X H Xu and G A Gehring, J Appl Phys 103, 023911 (2008)
• The dopant concentration and annealing temperature dependence of ferromagnetism in Co-doped ZnO thin films. X H Xu, X F Qin, F X Jiang, X L Li, Y Chen and G A Gehring, Appl Surf Sci 254 4956 (2008)
• Magnetoresistance in Co/ZnO Films. X L Li, Z Y Quan, X H Xu, H S Wu and G A Gehring, IEEE Trans Magnetics: 44, 2684 (2008).
• Two magnetic regimes in doped ZnO corresponding to a dilute magnetic semiconductor and a dilute magnetic insulator. A J Behan, A Mokhtari, H J Blythe, D Score, X H Xu, J R Neal, A M Fox and G A Gehring, Phys Rev Lett 100, 047206 (2008)
• Room-temperature magneto-optics of ferromagnetic transition-metal-doped ZnO thin films. J R Neal, A J Behan, R M Ibrahim, G A Gehring et al, Phys Rev Lett 96 (2006) 197208
• Carrier-induced ferromagnetism in n-type ZnMnAlO and ZnCoAlO thin films at room temperature. X H Xu, H J Blythe, M Ziese, G A Gehring et al, New Journal of Physics 8 (2006) 135. (This paper was chosen by the Editors of the IoP journals to be a ‘SELECT' publication.)

Current PhD students:

• David Score
• Marzook Alshammari
• Mohammed Al Qahtani
• Qi Feng

Current MSc and MPhys project students:

• Le Zhong
• Kiri Addison

Recently graduated PhD students:

• Abbas Mokhtari (October 2008)
• Anthony Behan (August 2008)
• Mohammed Ibrahim (January 2006)
• M Ahmed (November 2006)
• H Zenia (June 2006)
• M Croucher (July 1995)

Current active overseas collaborations:

• Xiao-Hong Xu (Shanxi Normal University China)
• Bijay Chaudhuri (IACS Calcutta India)
• Arghya Taraphder (IIT Kharagpur India)

Other Interests:

• Developing material to enthuse primary school children about science. The material is on the Institute of Physics web site, www.iop.org/pips (see Engaging the Public). I was the Principle Investigator on two EPSRC Partnership for Public Engagement Awards.
• Encouraging women to study physics and maintain a high profile career: publications below: