Steve Collins
Materials and Magnetism
Steve Collins is the Principal Beamline Scientist for I16 (Materials & Magnetism), and a visiting professor at Warwick University Physics Department. He obtained a PhD in nuclear spectroscopy from the University of Sussex before taking a post-doctoral position at Warwick, working on x-ray inelastic scattering and studies of magnetic materials. He worked at the SRS, Daresbury Laboratory from 1989, working mainly on diffraction beamlines and joined Diamond in 2003.
Email: Steve Collins
Tel: +44 (0) 1235 778087
Beamline I16: Materials and Magnetism
Key Research Areas
Research areas in recent years have centred on various aspects of x-ray physics with synchrotron radiation, often with the investigation of new experimental techniques as a principal goal. These have included resonant and non-resonant diffraction, Compton scattering and x-ray absorption spectroscopy.
Current Research Interests
One of my main activities concerns resonant x-ray diffraction, and specifically, studies of weak single-crystal diffraction peaks that exist due to anisotropy of the resonant scattering tensor. Such studies, which are expected to be a key activity of beamline I16, allow one to identify quadrupole and higher-order multipole anisotropy, magnetism, and resonant scattering processes that go beyond the electric dipole approximation in their description. An area of recent activity has been the identification of resonant scattering that arises from the evolution of the electronic state of an atom in a crystal, rather than the average state that is studied by most spectroscopies. While this field is in its infancy it is hoped that it will shed light on electronic properties of materials at elevated temperatures.
The Borrmann effect (thick crystal Laue case diffraction) is one the most celebrated dynamical diffraction phenomena, and has a detailed theoretical treatment dating to the 1960's. My interest in this phenomenon is to obtain a description of transmission close to absorption edges, where the resulting signals can be strongly affected by the unusual wave-field at the crystal planes.
Compton scattering provides a technique for studying the distribution of electron momenta in materials, and was one of the earliest indicators of the quantum nature of matter. Of recent interest has been the application of this technique to subtle aspects of magnetism.
X-ray dichroism of various forms continues to be of significant interest. Even in its simplest form – natural linear dichroism – it can play a major role in correcting, and helping to understand, resonant scattering phenomena. Strong linear dichroism can be used to characterise the polarization of x-ray scattering. Looking towards more exotic applications, we have embarked on a project with scientists from the Universities of Leicester and Cardiff, to assess the feasibility of using such materials for space-based x-ray telescopes.
Selected Publications
- Book: X-ray Scattering and Absorption by Magnetic Materials S W Lovesey and S P Collins, Oxford series on Synchrotron Radiation in Condensed Matter No. 1, Clarendon Press, March 1996
- Temperature-dependent forbidden resonant x-ray scattering in zinc oxide Collins SP, Laundy D, Dmitrienko VE, Mannix D, Thompson P PHYSICAL REVIEW B 68 064110 (2003)
- Design of a solid inclusion compound with optimal properties as a linear dichroic filter for X-ray polarization analysis Chao MH, Kariuki BM, Harris KDM, Collins SP, Laundy D ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 42 2982-2985 (2003)
- Direct observation of orbital ordering in La0.5Sr1.5MnO4 using soft x-ray diffraction Wilkins SB, Spencer PD, Hatton PD, Collins SP, Roper MD, Prabhakaran D, Boothroyd AT PHYSICAL REVIEW LETTERS 91 167205 (2003)
- X-ray Faraday rotation and magnetic circular dichroism in an iron-platinum compound S P Collins J.Phys.:Condens.Matter 11 1159 (1999)