Imperial College London

Professor Lesley F Cohen

Faculty of Natural SciencesDepartment of Physics

Consul for Faculty of Natural Sciences & Education Office
 
 
 
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Contact

 

+44 (0)20 7594 7598l.cohen CV

 
 
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Assistant

 

Mrs Carolyn Dale +44 (0)20 7594 7579

 
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Location

 

912Blackett LaboratorySouth Kensington Campus

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Summary

 

Overview

Research Background: Over the last few years we have built up a suite of novel characterisation tools for Functional Magnetic Materials. We can identify four main areas where we apply these tools;

a) Materials for Energy Efficient and Environmentally Friendly Magnetic Refrigeration

We are currently funded through an Innovate UK grant together with Camfridge UK to bring magnetic materials closer to application for domestic refrigeration. We have recently participated in a European wide programme on solid state magnetic cooling (DRREAM) and an EPSRC programme grant on materials for energy applications. We use our unique characterisation tools to study the magnetic, thermal and magnetocaloric properties of a range of materials. 

Low-temperature specific heat in hydrogenated and Mn-doped La(Fe,Si)13, Edmund Lovell, Luis Ghivelder, Amanda Nicotina, et al., Physical Rev B 94 134405  (2016)

Quantifying the deleterious role of strong correlations in La1-xCaxMnO3 at the magnetocaloric transition (vol 91, 134410, 2015) J.A. Turcaud, A.M. Pereira, L.F. Cohen, Physical Review B 91(13) 139902  (2015)

Dynamics of the First-Order Metamagnetic Transition in Magnetocaloric La(Fe,Si)13, Reducing Hysteresis,  E. Lovell, A.M. Pereira, A.D. Caplin, J. Lyubina and L.F. Cohen,  Advanced Energy Materials  5 (6) 1401639 (2015)

b) Solid Oxide Fuel Cell Materials

The work builds on the development of an optical fuel cell for monitoring Raman active processes in real time. We have used this system and a furnace Raman system to provide information on the reduction and oxidation processes associated with the formation of secondary phases in gadolinium doped ceria, one of the widely used electrolyte materials for solid oxide fuel cells.

Improving the performance of NiO-CGO cermets for fuel cell and electrolytic operation, Real time Monitoring using in-situ Raman spectroscopy, R. Maher, P.R. Shearing, E. Brightman et al., Advanced Science 3(1) 1500146 (2016)

Carbon deposition behaviour in metal-infiltrated gadolinia doped ceria electrodes for simulated biogas upgrading in solid oxide electrolysis cells, V. Duboviks, M. Lomberg, R.C. Maher, et al., Journal Of Power Sources  293  912-921 (2015)

 A Raman spectroscopic study of the carbon deposition mechanism on Ni/CGO electrodes during CO/CO2 electrolysis, V. Duboviks, R.C. Maher, M.  Kishimoto, L.F. Cohen, N.P. Brandon, G.J. Offer, Physical Chemistry Chemical Physics PCCP 16(26),13063-8 DOI,10.1039/c4cp01503g (2014)

Raman Spectroscopy of Solid Oxide Fuel Cells, Technique Overview and Application to Carbon Deposition Analysis,  R.C. Maher, V. Duboviks, G.J. Offer, et al., Fuel Cells 13 Special Issue, SI, 455-469   (2013)

 

c) Magnetoresistance sensors based on Narrow Gap Semiconductors (NGS): With recent EPSRC support we have worked on the growth, novel structural characterisation and magnetotransport properties of sub micron InSb quantum well materials for sensor applications.  We are also extending our studies to graphene.

Hexagonal boron nitride assisted transfer and encapsulation of large area CVD graphene, V. Shautsova, AM  Gilbertson, NCG Black, SA Maier, LF Cohen, Scientific Reports 6, 30210 (2016)

Plasmon-Induced Optical Anisotropy in Hybrid Graphene-Metal Nanoparticle Systems, A.M. Gilbertson, Y. Francescato, T. Roschuk, et al., Nano Letters  15(5)   Pages, 3458-3464   (2015)

Multifunctional semiconductor micro-Hall devices for magnetic, electric and photodetection, A.M. Gilbertson, Hatef Sadeghi, V. Panchal et al., App Phys Lett 107 233504 (2015)

Observation of spin dependent photocoductivity in InSb quantum well nanowires  Li, Juerong; Gilbertson, A. M.; Litvinenko, K. L.; et al. APPLIED PHYSICS LETTERS Volume: 101  Issue: 15  Article Number: 152407  DOI: 10.1063/1.4760223  Published: OCT 8 2012

Room temperature ballistic transport in InSb quantum well nanodevices Gilbertson, A. M.; Kormanyos, A.; Buckle, P. D.; et al.APPLIED PHYSICS LETTERS Volume: 99  Issue: 24  Article Number: 242101  DOI: 10.1063/1.3668107  Published: DEC 12 2011

 

d) Superconducting Materials: The effort in superconductivity research is an established activity in the group and we have an internationally recognised reputation in the development of characterisation tools such as length-scale analysis for examining the connectivity issue, flux creep (and the E-J-B surface), Hall probe imaging and a fast and ultra-sensitive calorimeter for studies of heat capacity of very small samples in high magnetic fields. More recently we have developed point contact spectroscopy (PCS) as a means to chart the evolution of the superconducting energy gap (D) in magnetic field

Magnetotransport of proton-irradiated BaFe2As2 and BaFe1.985Co0.015As2 single crystals, D. A. Moseley, K. A. Yates, N. Peng, D. Mandrus, A. S. Sefat, W. R. Branford, and L. F. Cohen, Phys. Rev. B 91, 054512  (2015)

Signatures of filamentary superconductivity in antiferromagnetic BaFe2As2 single crystals , D Moseley, KA Yates, WR Branford, AS Sefat, AS, D Mandrus, SJ Stuard; Stuard, S Salem-Sugui, L Ghivelder and LF Cohen, European Physical Letters 111 (3) 37005 (2015)

Evidence for nodal superconductivity in Sr2ScFePO3  Yates, K. A.; Usman, I. T. M.; Morrison, K.; et al: SUPERCONDUCTOR SCIENCE & TECHNOLOGY Volume: 23  Issue: 2  Article Number: 022001  DOI: 10.1088/0953-2048/23/2/022001  Published: FEB 2010

e) Harnessing Electron Spin: Over the last few years the group have been funded to look at highly spin polarised magnetic oxides such as manganites and CrO2 as well as Heusler alloys such as NiMnSb and Co2MnSi using Andreev spectroscopy. Most recently we have studied Andreev signatures associated with the formation of spin triplet superconductivity in ferromagnetic metals when in close proximity to a superconductor.

 Evidence for spin mixing in holmium thin film and crystal samples (vol 83, 144518, 2011) Usman, I. T. M.; Yates, K. A.; Moore, J. D.; et al.: PHYSICAL REVIEW B Volume: 84  Issue: 13  Article Number: 139904  DOI: 10.1103/PhysRevB.84.139904  Published: OCT 14 2011;PHYSICAL REVIEW B Volume: 83  Issue: 14  Article Number: 144518  DOI: 10.1103/PhysRevB.83.144518  Published: APR 21 2011

Coexistence of Universal and Topological Anomalous Hall Effects in Metal CrO2 Thin Films in the Dirty Limit  Branford, W. R.; Yates, K. A.; Barkhoudarov, E.; et al. PHYSICAL REVIEW LETTERS Volume: 102  Issue: 22  Article Number: 227201  DOI: 10.1103/PhysRevLett.102.227201  Published: JUN 5 2009

 

 

FUNDING TRACK RECORD  

Grant PI Funder Reference Start date Title Amount
PI Klein EPSRC EP/K016407/1 01-02-2013 31-01-2015 Integrated graphene - based sensor devices via scalable microfabrication process development based on graphene - metal multilayer deposition  1,370,064
PI  Sandeman EC - CP-FP 310748-2  DRREAM  CP 01-01-2013 31-12-2015 Drastically Reduced Rare Earth use in Applications of magnetocalorics 625,000
PI-Branford Leverhulme Trust 17466 01-09-2012 31-08-2015 Imaging low temperature phases in artificial spin ice: ICE-COLD 223,899
PI Cohen EPSRC EP/J014699/1 14-11-2012 13-11-2015 Ultra-High resolution, ultra-sensitive multifunctional ballistic nano sensors for the simultaneous detection of magnetic, electric and optical fields.   493,258
PI Skinner EPSRC EP/J003085/1 01-06-2012 31-05-2015 Multiscale in-situ characterisation of degradation and reactivity in solid oxide fuel cells  816,651
PI-Cohen EPSRC EP/H040048/1 01-04-10 31-05-13 Superconducting Gap Structure and Symmetry in Fe Based Superconductors. 445,842
PI – Alford EPSRC EP/G060940/1 01-10-09 30-09-14 Nanostructured Functional Materials for Energy Efficient Refrigeration, Energy Harvesting and Production of Hydrogen from Water. 3,863,046  
PI-Cohen (Imperial College node) PI-Sandeman EC* FP7-NMP-214864 01-10-09 30-09-11 Solid State Energy Efficient Cooling – SSEEC Sandeman  grant co-ordinator and Cambridge node until 2009) 210,000 325,000
PI-Cohen EPSRC EP/F016271/1 01-10-08 30-09-11 Inhomogeneous magnetism and superconductivity 98,622
PI-Cohen EPSRC EP/F065922/1  01-09-08 31-08-11 Extraordinary Magnetoresistance NanoSensors- Fundamental Issues and Applications 481,298.
PI-Cohen Leverhulme Trust F/07 058/AW 01-09-08 31-01-12 Defects in 2D frustrated prototype spin ice systems – DEFROST 192,585
PI-Cohen EPSRC EP/D063329/1 01-03-2007 28-02-2013 New Tools for Nanometrology 2,719,793
PI-Cohen EPSRC EP/E016243/1 01-06-2007 31-05-2012 A Platform to Develop and Utilise Characterisation Tools for Functional Magnetic Materials 730,000
PI Cohen, EPSRC EP/C511972/1 01-05-2005 30-04-2008 Materials Engineering To Optimise The Spin Dependent Transport Between Ferromagnetic Metals and Narrow Gap Semiconductors 610,488

Research Staff

Gilbertson,A

Maher,MR

Morrison,K

Pereira,A

Perkins,G

Yates,K

Research Student Supervision

Brown,L, Thermal and electrical properties od carbon nanotubes

Cowie,A, A Study of the Microwave Power dependance in HTS thim Films

Ghosh,IS, Microwave Losses of HTS thin films induced by High Magnetic Field

Hossain,AKM, Investigation of the Colassal Magnetoresistance bulk and Thick Film Manganites

Hudson,P, Transport and MFM of CMR

Magnus,F, Spintronics

Maher,R, SERS

Malde,N, Ramon Spectroscopy of cuprate and manganite oxides

Miyoshi,Y, Point Contact Spectroscopy

Moore,J, Critical fields in MgB2

Morrison,K, Magnetocalorics

Morrison,K

Moseley,D

Purnell,A, Nonlinear effects in HTS Thin Films

Tarcaud,J

Totty,J, Vortex Dynamics in the Cuprate Superconductors

Wickens,E, Superconductivity

Yates,K, Microwave properties of Manganites