Dr
Ross
Stewart
LET Instrument Scientist
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No
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​​​LET Instrum​​ent S​​cien​​tist

​Excitati​​ons Group​​​






Recent Public​​ati​​ons

 

A. Arbe, G J Nilsen, J R Stewart, F Alvarez, V Garcia Sakai and J Colmenero

Coherent structural relaxation of water from meso- to intermolecular scales measured using neutron spectroscopy with polarization analysis. 

Phys. Rev. Research 2022015(R) (2020)


H Jacobsen, C D Dashwood, E Lhotel, D Khalyavin, P Manuel, J R Stewart, D Prabhakaran, D F McMorrow, and A T Boothroyd 

Strong quantum fluctuations from competition between magnetic phases in a pyrochlore lattice 

Phys. Rev. B 101 104404 (2020)


T Chen, Y Chen, A Kreisel, X Lu, A Schneidewind, Y Qiu, J T Park, T G Perring, J R Stewart, H Cao, R Zhang, Y Li, Y Rong, Y Wei, B M Andersen, P J Hirschfeld, C Broholm, and P Dai

Anisotropic spin fluctuations in detwinned Fe​Se

Nature Materials 

18 709–716 (2019)

M Bieringer, J R Stewart, A P Grosvenor, M Dragomir, and J E Greedan

Quenching of Long Range Or​​der and the Mn3+ Ordered Moment 

in the Layered Antiferromagnet, BaxSr1–xLaMnO4. A Polarized Neutron Scattering Study

Inorg. Chem. 

58 4300–4309 (2019)

R A Ewings, J R Stewart, T G Perring, R I Bewley, M D Le, D Raspino, D E Pooley, G Skoro, S P Waller, D Zacek, C A Smith, and R C Riehl-
Shaw

Upgrade to the MAPS neutron time-of-f​​​light chopper spectrometer

Rev. Sci. Instr. 90 035110 (2019)

J R Stewart, S R Giblin, D Honecker, P Fouquet, D Prabhakaran, and J W Taylor
  • Transverse and longitudinal spin-fluctuations in INVAR Fe0.65Ni0.35​​
  • J. Phys.: Condens. Matter 31 025802 (2019)
  • 10.1088/1361-648X/aaeeaf
     

  • J A M Paddison, M J Gutmann, J R Stewart, M G Tucker, M T Dove, D A Keen, and A L Goodwin
  • Magnetic structure of paramagnetic MnO
  • Phys. Rev. B 97 014429 (2018)
  • H Chang, I-Y Hwang, J-H Chung, J R Stewart, W Higemoto, and Y Miyake
  • Temperature dependence of magnetic excitations in the frustrated antiferromagnetic spinel ZnMn2O4
  • Phys. Rev. B 97 014406 (2018)

Research Interests

​​S​truct​​ure and dynamics of frustrated magnets

​Frustrated magnets are fascinating model systems in which the lattice topology and/or mixed magnetic interactions can lead to an extensively degenerate magnetic ground state. This leads to novel magnetic structural and dynamical properties in these materials.  Ross has, over the years, investigated various metallic frustrated magnets (β-Mn, YMn2, INVAR) mainly using neutron polarization analysis,  inelastic neutron scattering and muon spin relaxation (μSR) techniques.  He is also interested in the magnetic structural and dynamical properties of antiferromagnetic pyrochlore lattices (Gd2Ti2O7, Gd2Sn2O7) and kagome lattice (herbertsmithite, swedenborgite) materials. This work is done in collaboration with  Dr Joe Paddison (ORNL) and Dr. Andrew Goodwin (Oxford), addition to various other UK and international research teams.

Selected Publications:​

J A M Paddison, G Ehlers, O A Petrenko, A R Wildes, J S Gardner, and J R Stewart
Spin correlations in the dipolar pyrochlore antiferromagnet Gd2Sn2O7
J. Phys.: Condens. Matter 29 144001 (2017)
10.1088/1361-648X/aa5d2e

J A M Paddison, J R Stewart, P Manuel, P Courtois, G J McIntyre, B D Rainford, and A L Goodwin
Emergent Frustration in Co-doped beta-Mn
  • Phys. Rev. Lett. 110 267207 (2013)

G J Nilsen, M A De Vries, J R Stewart, A Harrison, and H M Ronnow
 
 

A M Hallas, J A M Paddison, H J Silverstein, A L Goodwin, J R Stewart, A R Wildes, J G Cheng, J S Zhou, J B Goodenough, E S Choi, G Ehlers, J S Gardner, C R Wiebe, and H D Zhou 
Statics and dynamics of the highly correlated spin ice Ho2Ge2O7
Phys. Rev. B 86 134431 (2012)

J R Stewart, G Ehlers, A S Wills, S T Bramwell, and J S Gardner 
Comment on “Magnetic structure of Gd2Ti2O7
Phys. Rev. B 85 106401 (2012)

G J Nilsen, F C Coomer, M A De Vries, J R Stewart, P P Deen, A Harrison, and H M Ronnow
Pair correlations, short-range order, and dispersive excitations in the quasi-kagome quantum magnet volborthite. 
Phys. Rev. B 84 172401 (2011)

J R Stewart, J M Hillier, P Manuel, and R Cywinski 
A neutron polarization analysis study of moment correlations in (Dy0.4Y0.6)T2 (T = Mn, Al) 
J. Phys.: Condens. Matter  23 164205 (2011)

J S Gardner, G Ehlers, P Fouquet, B Farago, and J R Stewart 
Slow and static spin correlations in Dy2+xTi2−xO7−δ 
J. Phys.: Condens. Matter  23 164220 (2011)

J R Stewart, G Ehlers, H Mutka, P Fouquet, C Payen, and R Lortz
Spin dynamics, short-range order, and spin freezing in Y0.5Ca0.5BaCo4O7
Phys. Rev. B 83 024405 (2011)


​Polarized Neutron Scatte​​ring

Between 1998 and 2008, Ross worked at the Institut Laue-Langevin in Grenoble, where he led the redesign and reconstruction of the diffuse scattering spectrometer, D7, as part of the ILL Millennium Programme.   He designed a novel supermirror spin-analyser array for D7 which provided a factor of 60 increase in count-rate of this instrument.  At ISIS, from 2010-2017 Ross led the projects to bring 3He MEOP spin-filters to beamlines such as LARMOR and LET.  The LET spectrometer has recently been equiped with neut​ron polarization analysis using a combination of a supermirror polarizer and 3He wide-angle analyser system.  First experiments are now being performed, and Ross now provides experimental support.  

Selected Publications:​

 
 
  • A. Arbe, G J Nilsen, J R Stewart, F Alvarez, V Garcia Sakai and J Colmenero

    Coherent structural relaxation of water from meso- to intermolecular scales measured using neutron spectroscopy with polarization analysis. 

    Phys. Rev. Research 2022015(R) (2020)



  • J R Stewart, S R Giblin, D Honecker, P Fouquet, D Prabhakaran, and J W Taylor
    • Transverse and longitudinal spin-fluctuations in INVAR Fe0.65Ni0.35​​
    • J. Phys.: Condens. Matter 31 025802 (2019)
    • 10.1088/1361-648X/aaeeaf

G M Paterno, J R Stewart, A R Wildes, F Cacialli, and V Garcia-Sakai
Neutron polarisation analysis of Polymer: Fullerene blends for organic photovoltaics
Polymer 105 407–413 (2016)
​​
G Ehlers, J R Stewart, A R Wildes, P P Deen, and K H Andersen
Gener
alization of the classical xyz-polarization analysis technique to out-of-plane and inelastic scattering
Rev. Sci. Instrum84 093901 (2013)
2013 | journal-article

J R Stewart, P P Deen, K H Andersen, H Schober, J-F Barth ́el ́emy, J M Hillier, A P Murani, T Hayes, and B Lindenau
Disordered materials studied using neutron polarization analysis on the multi-detector spectrometer, D7
J. Appl. Cryst. 42 69–84 (2009)


Co-funded Research Students

Philip Welch (University of Oxford) 2015-
Toby Willis (Royal Holloway) 2013-2016
Joe Paddison (Univeristy of Oxford) 2012-2016
Giovanni Pasquino (Royal Holloway) 2011-2015
Clare Leavey (University of Southampton) 2004-2008
Judith Preston (University of Leeds) 1999-2002
Charlotte Anderson (University of Liverpool) 1998-1999​​

​​External Bodies​

  • Editorial board: J. Phys: Condens. Matter (Magnetism section)
  • Member of the Institute of Physics (CPhys MInstP)
​Teac​hing

ORCID

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