Helen Walker
Instrument scientist
Email address:
Helen is a senior scientist with the ISIS Excitations Group working on the development of barocalorics for green energy applications, and fundamental magnetism.
Introduction
I am an inelastic neutron scattering scientist, taking advantage of how neutrons interact with matter to investigate the dynamics and structure of functional materials. I also have considerable previous experience of working with X-rays; after spending several years working at synchrotrons in France and Germany.
My particular interests have evolved from exploring the magnetic properties of f-electron systems and transition metal oxides, particularly multiferroics and 5d systems, and more recently hybrid organic-inorganic materials such as Metal-Organic Frameworks (MOFs); to investigating lattice dynamics in technologically relevant materials. This resulted in being co-PI on an EPSRC grant to study phonons under pressure in barocaloric MOFs using neutrons in collaboration with Prof Anthony Phillips at QMUL (2019-2022). We examined a range of barocalorics using various neutron scattering techniques: nPDF, QENS and INS, with the aim of understanding what drives the large entropy change required for barocaloric cooling applications. Continuing this collaboration, we are now including advanced Molecular Dynamics simulations to assist in our search for optimised barocalorics under EPSRC grant “Barocalorics for Green Cooling” with Dr Keith Butler at UCL (2026-2029)
Teaching and Supervision
I currently supervise PhD student Peter Dung Nguyen-Minh with Anthony. Previously I supervised: Bernet Meijer (PhD 2023), and Richard Dixey (PDRA 2019-2023).
I was the co-chair of the ISIS Brazil neutron scattering school in September 2024, and was the course co-ordinator for the ISIS Neutron Training Course 2014-2022, which runs annually for 35 participants to get hands on experience of using ISIS instruments. I have also lectured on neutron scattering at the Parana Neutron Scattering School, Institute for Materials Discovery at University College London, the Nanotechnology Centre at the Gdansk University of Technology and the SISN Advanced School on Magnetism in Ispra, Italy.
Conference organisation
Co-chair of Solid Materials for Sustainable Cooling—Caloric Effects and Devices Symposium at MRS Spring 2025 in Seattle WA (7-11 April)
Co-chair of Neutron scattering enabled energy materials design at MRS Spring 2023 in San Francisco CA (10-14 April 2023)
Selected publication highlights
- On (not) deriving the entropy of barocaloric phase transitions from crystallography and neutron spectroscopy, J. Phys. Energy. 6, 011001 (2023)
- Dynamics in the ordered and disordered phases of barocaloric adamantine, Phys. Chem. Chem. Phys. 25, 9282 (2023)
- Origin of the large entropy change in the molecular caloric and ferroelectric ammonium sulfate, Adv. Func. Mat. 32, 2207717 (2022)
- Pressure dependence of rotational dynamics in barocaloric ammonium sulfate, Phys. Rev. B 106, 064302 (2022)
- Chapter 5: Inelastic neutron scattering under pressure, De Gruyter, 139-158 (2022)
- Low thermal conductivity in a modular inorganic material with bonding anisotropy and mismatch, Science 373, 1017 (2021)
- Magnetic structure and spin wave excitations in the multiferroic magnetic metal-organic framework (CD3)2ND2[Mn(DCO2)3], Phys. Rev. B 96, 094423 (2017)
- Evidence for a spinon Fermi surface in a triangular lattice quantum spin liquid candidate, Nature 540, 559 (2016)
- Femtoscale magnetically induced lattice distortions in multiferroic TbMnO3, Science 333, 1273 (2011)
- Circularly Polarized X-Rays as a Probe of Noncollinear Magnetic Order in Multiferroic TbMnO3 Phys. Rev. Lett. 102, 237205 (2009)
