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. I also expand on this to study phase transitions in other materials that can be modelled by a pseudo-spin formulation.
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). Part of this work is funded by a Leverhulme Emeritus Fellowship.

I also have Royal Society funded collaboration with Moscow MISiS to study multiferroic manganites also active collaborations with groups in Saudi Arabia (KACST), China (Academy of Science Beijing and Xanxi Normal University), Sweden (KTH) and also with the USA (Argonne National Laboratory)
Since I retired I became an Emeritus Professor and am devoting almost all my time to research and also to some outreach activities.

Recent theoretical papers include:

• Complex multicolor tilings and critical phenomena in tetraphilic liquid crystals Xiangbing Zeng, Robert Kieffer, Benjamin Glettner, Constance Nürnberger, Feng Liu, Karsten Pelz, Marko Prehm, Ute Baumeister, Harald Hahn, Heinrich Lang, Gillian A. Gehring, Christa H. M. Weber, Jamie K. Hobbs, Carsten Tschierske and Goran Ungar Science 331, 1302 (2011)
• Carrier-mediated nonlocal ferromagnetic coupling between local magnetic polarons in diluted magnetic oxide semiconductors Shifei Qi, F. Jiang, J. Fan, SB Zhang, GA. Gehring, Zhenyu Zhang, XH Xu Phys Rev B 84, 205204 (2011)
• Landau theory of compressible magnets near a quantum critical point Gillian A Gehring and Mahrous R. Ahmed Proc MMM-Intermag J. Appl Phys 107, 09E125 (2010)
• Multiple Scattering Between Cylinders and a Schroeder Diffuser M.A. Pogson, D.M. Whittaker, G.A. Gehring, R.J. Hughes, J.A.S. Angus, T.J. Cox Acta Acustica United with Acustica 96, 292 (2010)
• 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)

Recent experimental publications include:

• Magneto-optic studies of magnetic oxides GA Gehring, MS Alshammari, DS Score, JN Neal, A Mokhtari, AM Fox J. Mag. Mag. Mater published on line (2012)
• Room temperature ferromagnetism in metallic and insulating (In1-xFex)2O3 thin films F.X.Jiang, X.H. Xu, J. Zhang, X.C. Fan, H.S. Wu, M. Alshammari, Q. Feng, H.J. Blythe, D.S. Score, K. Addison,; M. Al-Qahtani, G.A. Gehring J. Appl Phys 109 053907 (2011)
• Donor-band ferromagnetism in cobalt-doped indium oxide A. M. H. R. Hakimi, M.G Blamire, S.M. Heald, M.S. Alshammari, M.S. Alqahtani, D.S. Score, H.J. Blythe, A.M Fox, G.A. Gehring Phys Rev B 84, 085201 (2011)
• Structure and magnetotransport in Co/nonmagnetic films Z.Y. Quan, W. Liu, Zhi-Yong, X.L. Li, Xiao-Li, X. H. Xu, K. Addison, D.S. Score, G.A. Gehring Mater. Lett 65, 2982 (2011)
• Role of carrier and spin in tuning ferromagnetism in Mn and Cr-doped In2O3 thin films Feng-Xian Jiang, Xiao-Hong Xu, Jun Zhang, Xiao-Chen Fan, Hai-Shun Wu, G. A. Gehring Appl Phys Lett 96, 052503 (2010)
• Room temperature ferromagnetism in pristine MgO thin films C. Moyses Araujo, Mukes Kapilashrami, Xu Jun, O. D Jayakumar, Sandeep Nagar, Yan Wu, Cecilia Arhammar, Borje Johansson, Lyubov Belova, Rajeev Ahuja, Gillian A. Gehring, K.V. Rao Appl. Phys. Lett. 96, 232505 ( 2010)
• Investigation of structure and magnetoresistance in Co/ZnO films Z.Y. Quan, Zhi-Yong, X. H. Xu, X.L. Li, Xiao-Li, Q. Feng, G.A. Gehring J. Appl Phys 108, 103912 (2010)
• 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 La0.7Sr0.3MnO3 thin films. T K Nath, J R Neal and G A Gehring, J. Appl Phys 105, 07D709 (2009)
• Spin-polarized transport current in n-type codoped ZnO thin films measured by Andreev spectroscopy KA Yates KA, AJ Behan, JR Neal , DS Score HJ Blythe, GA Gehring, SM Heald, WR Branford, LF Cohen Phys Rev B 80, 245207 (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)
• 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)
• 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.) 

Senior vistors:

• Minju Ying (November 2011-November 2012)
• Xiaoli Li (September 2012 –August 2013)
• Marzook Alshammari (September 2012- December 2012)

Current PhD students:

• Mohammed Al Qahtani
• Qi Feng
• Hasan Al-Bargi
• Wala Dizayee
   

MSc and MPhys project students 2011-2012:

• Timothy Farrow
• Rania Alqurashi
• Ahmed Taha
• Christopher Bentham
• Stuart George

Recently graduated PhD students:

• Marzook Alshammari (January 2012)
• Abbas Mokhtari (October 2008)
• Anthony Behan (August 2008)
• Mohammed Ibrahim (January 2006)
• M Ahmed (November 2006)
• H Zenia (June 2006)

Current active overseas collaborations:

• Ahmed Alymani and Marzook Alshammari KACST Saudi Arabia
• Xiao-Hong Xu Shanxi Normal University China
• Tao Xiang Academy of Sciences Beijing China
• Yakov Mukovskii MISiS Moscow Russia
• KV Rao KTH Stockholm
• 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:

• "PhD’s are worth more for women" G A Gehring Physics World September 2001 http://physicsweb.org/articles/world/14/9/2
• Letter to Physics World December 2001 G A Gehring "Unretiring Women"
• "Mixing motherhood with science" G A Gehring Physics World March 2002 http://physicsweb.org/articles/world/15/3/3. This was reprinted by www.Science.Careers.org and is high on the google ‘hit list’. It still generates emails to GAG from around the world.
• "Women physicists speak" G A Gehring and six other members of the UK team who attended the first IUPAP conference on women in Physics in Paris 2002.