Paul Steadman

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Paul Steadman is a Principal Beamline Scientist working on beamline I10.  Paul joined Diamond in 2003 after working at the University of Leeds.

Email: paul.steadman@diamond.ac.uk
Tel: +44 (0) 1235 778156

Key Research Area

Key Research


Magnetism Thin Films Surfaces and Interfaces Condensed Matter Physics

Research Expertise

  1. Research Expertise
  2. Collaborators
  3. Publications
  4. Biography
Research Expertise -

Current Research Interests

Magnetism is a phenomenon which has perplexed and amazed for hundreds of years. One of the difficulties in its understanding is due to the need for relativity and quantum mechanics to explain magnetic properties; these two subjects were not developed until the twentieth century. One of the great breakthroughs in magnetism came when the property of magnetoresistance was discovered in thin films of chromium and iron in 1988. This discovery led to new sensitive read heads for hard drives allowing higher data storage densities to be reached. The two principal scientists involved, Peter Grunberg and Albert Fert, were awarded the Nobel Prize for this discovery in 2007.

Another property needed by a read head, or spin valve, in a hard drive is the exchange bias effect. Exchange bias occurs when a ferromagnetic material (with spontaneous magnetism) is in proximity to an antiferromagnetic (no spontaneous magnetism). Normally the magnetism of a thin film of a magnetic material can easily be turned in any direction by applying a suitable magnetic field. In an exchange biased thin ferromagnetic film it takes a lot more magnetic energy to "flip" the field. The magnet is trapped due to its interaction with the antiferromagnet. This effect is vital for the operation of a spin valve. Despite this the exchange bias effect, which was discovered in the 1950s, is still poorly understood. Our particular project is looking at the effect of disorder on the exchange bias. In a most recent experiment it has been discovered that the exchange bias field (amount of applied field needed to flip the magnetism of the ferromagnet) depends on the disorder in the antiferromagnet.

Another area of research involves trying to control the direction of a magnetic field using a voltage rather than a current. This can be achieved using materials known as multiferroics. Unfortunately multiferroics are rare and are mostly ony multiferroic at low temperatures which are not very practical for use in devices. We are exploring multiferroism in artificially grown materials to overcome these problems. In one case we are examining the exchange bias interaction betwen a magnetic thin film (cobalt) and an antiferromagnetic magnetoelectric.

In addition to the research I am also in charge of beamline I10, otherwise known as the Beamline for Advanced Dichroism Experiments. I schedule the user experiments, maintain the beamline, realise upgrade projects, help with recrutement of new staff (for I10 and other beamlines) and manage the four staff members on the beamline. I also supervise a student that I share with ISIS and the University of Leeds.

Collaborators - +

Collaborators

With scientists from the University of Leeds and ISIS we are examining the magnetic fluctuations in frustrated systems. Frustration arises when nearest neighbour interactions cannot be fulfilled due to the crystal structure. These materials do not obey the third law of thermodynamics since there can be many ground states at zero kelvin. By growing artificial systems we have been able to look at the interactions between islands over periods of several hours at different temperatures.

 

Publications - +

Publications

  • RASOR: An advanced intrument for soft X-ray reflectivity and diffraction T. A. W. Beale, T. P. A. Hase, T. Lida, K. Endo, P. Steadman, A. R. Marshall, S. S. Dhesi, G. van der Laan and P. D. Hatton Review of Scientific Instruments 81, 073904 (2010).
     
  • Probing magnetic ordering in multilayers using soft X-ray resonant magnetic scattering C. H. Marrows, P. Steadman, A. C. Hampson, L.-A. Michez, B. J. Hickey, N. D. Telling and D. A. Arena Physical Review B 72 024421 (2005)
Biography - +

Biography

Paul Steadman has been involved in research of magnetic systems for nearly twenty years. Graduating with a first class honours degree in Physics he went on to do a PhD using surface X-ray diffraction to look at the structure and disorder in magnetic systems. Following this he obtained a postdoctoral position at the European Synchrotron Radiation Facility (ESRF), Grenoble, where he also used surface X-ray diffraction to study structure, however, this was also used in resonant mode so that the X-ray were directly sensitive to magnetism.

Whilst at the ESRF he built an optical system to measure magnetism at surfaces. In addition work on stepped surfaces showed that surfaces relaxations could penetrate deep into the surface due to strong interaction between steps. Following the ESRF Paul went on to work at the University of Leeds where he used neutron and X-ray scattering to study magnetic disorder. In addition to the hard X-rays he already had experience with he started to use the soft X-ray energy range. Neutron reflectivity work on an artificially produced exchange biased system demonstrated the importance of the anisotropy in the antiferromagnet for exchange bias to occur.

After Leeds Paul joined diamond to help build a beamline optimised for studies with a photoemission electron microscope with Sarnjeet Dhesi. Shortly after commissioning of the beamline he obtained the position of Principal Beamline Scientist on I10, the Beamline for Advanced Dichroism Experiments (BLADE). After the design, procurement of components, construction and commissioning the beamline was ready for users in December 2010. He now manages the beamline and continues his work on exchange bias and magnetic disorder.

He is currenlty attempting some work on articially produced multiferroics. In addition to his research Paul has a passion for teaching science to people. He has given several seminars to a general audience plus a seminar about music and science at the Didcot Arts centre.