School of Physics and Astronomy

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Dr Oscar Cespedes

Condensed Matter Group

Contact details

Room: 8.302
Tel: +44 (0)113 3431885
Email: o.cespedes @ leeds.ac.uk

Keywords

Spintronics
Carbon nanomaterials
C60 magnetic tunnel junctions
Spin transport in graphene and carbon nanotubes
Biomagnetism
Exobiology
Raman spectroscopy
Magnetometry

Research interests

My research interests cover a broad range of topics, including:

1.- Electron and spin dependent transport in carbon based materials, such as magnetic tunnel junctions with buckyballs(C60), and spintronics in graphene, carbon nanotubes and other organics.

2.- Magnetic field dependent transport in nanostructures, such as magnetic oxide nanoconstrictions (Fe3O4, NiOx, LSMO) and gas-stabilised break junctions.

3.- The electron/spin-phonon interaction in hybrid devices (probed by Raman, Brillouin light scattering and other techniques).

4.- Biomagnetism and novel mechanisms of interactions between RF/microwave magnetic fields and proteins.

5.- Exobiology and protein dynamics in conditions simulating those of other planets and/or outer space, including Raman microscopy at low temperatures (down to ~3 K) or under simulated microgravity using magnetic fields.

6.- The magnetic and optical properties of magnetic nanoparticles for device and biological applications.

Useful links

Research website
Group website

Publications

Kulmaczewski R, Cespedes O, Halcrow MA Gradual Thermal Spin-Crossover Mediated by a Reentrant Z' = 1→ Z' = 6 → Z' = 1 Phase Transition. Inorg Chem 56 3144-3148, 2017
DOI:10.1021/acs.inorgchem.7b00071
View abstract

Fang Z, Mitra A, Westerman AL, Ali M, Ciccarelli C, Cespedes O, Hickey BJ, Ferguson AJ Thickness dependence study of current-driven ferromagnetic resonance in Y3Fe5O12/heavy metal bilayers Applied Physics Letters 110 -, 2017
DOI:10.1063/1.4977490
View abstract

Talalaevskij A, Decker M, Stigloher J, Mitra A, Körner HS, Cespedes O, Back CH, Hickey BJ Magnetic properties of spin waves in thin yttrium iron garnet films Physical Review B - Condensed Matter and Materials Physics 95 -, 2017
DOI:10.1103/PhysRevB.95.064409
View abstract

Halcrow MA, Kulmaczewski RL, Cespedes O Data to support study of Gradual Thermal Spin-Crossover Mediated by a Re-Entrant Z? = 1 to Z? = 6 to Z? = 1 Phase Transition., 2017
DOI:10.5518/164

Kulak AN, Grimes R, Kim YY, Semsarilar M, Anduix-Canto C, Cespedes O, Armes SP, Meldrum FC Polymer-Directed Assembly of Single Crystal Zinc Oxide/Magnetite Nanocomposites under Atmospheric and Hydrothermal Conditions Chemistry of Materials 28 7528-7536, 2016
DOI:10.1021/acs.chemmater.6b03563
View abstract

Cepriá G, Córdova WR, Céspedes O, Sánchez-García L, Ferrer P, Gianolio D, Castillo JR Physical and chemical characterization of cerium(IV) oxide nanoparticles Analytical and Bioanalytical Chemistry 408 6589-6598, 2016
DOI:10.1007/s00216-016-9771-x
View abstract

Ye S, Benz F, Wheeler MC, Oram J, Baumberg JJ, Cespedes O, Christenson HK, Coletta PL, Jeuken LJC, Markham AF, Critchley K, Evans SD One-step fabrication of hollow-channel gold nanoflowers with excellent catalytic performance and large single-particle SERS activity Nanoscale 8 14932-14942, 2016
DOI:10.1039/c6nr04045d
View abstract

Shamba P, Morley NA, Cespedes O, Reaney IM, Rainforth WM Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe11.6Si1.4 Applied Physics A: Materials Science and Processing 122 -, 2016
DOI:10.1007/s00339-016-0253-y
View abstract

Henrichs LF, Cespedes O, Bennett J, Landers J, Salamon S, Heuser C, Hansen T, Helbig T, Gutfleisch O, Lupascu DC, Wende H, Kleemann W, Bell AJ Multiferroic Clusters: A New Perspective for Relaxor-Type Room-Temperature Multiferroics ADVANCED FUNCTIONAL MATERIALS 26 2111-2121, 2016
DOI:10.1002/adfm.201503335

Cook LJK, Kulmaczewski R, Cespedes O, Halcrow MA Different Spin-State Behaviors in Isostructural Solvates of a Molecular Iron(II) Complex Chemistry - A European Journal 22 1789-1799, 2016
DOI:10.1002/chem.201503989
View abstract

Al Ma'Mari F, Moorsom T, Teobaldi G, Deacon W, Prokscha T, Luetkens H, Lee S, Sterbinsky GE, Arena DA, MacLaren DA, Flokstra M, Ali M, Wheeler MC, Burnell G, Hickey BJ, Cespedes O Beating the Stoner criterion using molecular interfaces. Nature 524 69-73, 2015
DOI:10.1038/nature14621
View abstract

Kershaw Cook LJ, Thorp-Greenwood FL, Comyn TP, Cespedes O, Chastanet G, Halcrow MA Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn-Teller Distortion Inorganic Chemistry 54 6319-6330, 2015
DOI:10.1021/acs.inorgchem.5b00614
View abstract

Popuri SR, Redpath D, Chan G, Smith RI, Cespedes O, Bos JWG Antisite-disorder, magnetic and thermoelectric properties of Mo-rich Sr<inf>2</inf>Fe<inf>1-y</inf>Mo<inf>1+y</inf>O<inf>6</inf> (0≤ y ≤ 0.2) double perovskites Dalton Transactions 44 10621-10627, 2015
DOI:10.1039/c4dt03307h
View abstract

Cook LJK, Shepherd HJ, Comyn TP, Baldé C, Cespedes O, Chastanet G, Halcrow MA Decoupled spin crossover and structural phase transition in a molecular iron(II) complex Chemistry - A European Journal 21 4805-4816, 2015
DOI:10.1002/chem.201406307
View abstract

Santoro A, Kershaw Cook LJ, Kulmaczewski R, Barrett SA, Cespedes O, Halcrow MA Iron(II) complexes of tridentate indazolylpyridine ligands: Enhanced spin-crossover hysteresis and ligand-based fluorescence Inorganic Chemistry 54 682-693, 2015
DOI:10.1021/ic502726q
View abstract

Chowdhury M, Oputu O, Kebede M, Cummings F, Cespedes O, Maelsand A, Fester V Rapid and large-scale synthesis of Co3O4octahedron particles with very high catalytic activity, good supercapacitance and unique magnetic properties RSC Advances 5 104991-105002, 2015
DOI:10.1039/c5ra20763k
View abstract

Mari FAM, Moorsom T, Teobaldi G, Deacon W, Prokscha T, Luetkens H, Lee S, Sterbinsky GE, Arena DA, MacLaren DA, Flokstra M, Ali M, Wheeler MC, Burnell G, Hickey B, Cespedes O Beating the Stoner Criterion, 2015
DOI:10.5518/6

Cespedes O, Wheeler M, Moorsom T, Viret M Unexpected magnetic properties of gas-stabilized platinum nanostructures in the tunneling regime Nano Letters 15 45-50, 2014
DOI:10.1021/nl504254d
View abstract

Ma'Mari FA, Wheeler M, Kendric E, Burnell G, Hickey BJ, Moorsom T, Cespedes O Direct Measurement of spin polarization in ferromagnetic-C60 interfaces using point-contact andreev reflection IEEE Transactions on Magnetics 50 -, 2014
DOI:10.1109/TMAG.2014.2322658
View abstract

Moorsom T, Wheeler M, Mohd Khan T, Al Ma'Mari F, Kinane C, Langridge S, Ciudad D, Bedoya-Pinto A, Hueso L, Teobaldi G, Lazarov VK, Gilks D, Burnell G, Hickey BJ, Cespedes O Spin-polarized electron transfer in ferromagnet/C60 interfaces Physical Review B - Condensed Matter and Materials Physics 90 -, 2014
DOI:10.1103/PhysRevB.90.125311
View abstract

Kulmaczewski R, Shepherd HJ, Cespedes O, Halcrow MA A homologous series of [Fe(H₂Bpz₂)₂(L)] spin-crossover complexes with annelated bipyridyl co-ligands. Inorg Chem 53 9809-9817, 2014
DOI:10.1021/ic501402q
View abstract

Venugopal A, Cespedes O, Russell SJ Controlling dielectric and magnetic properties of PVdF/Magnetite nanocomposite fibre webs. International Journal of Polymer Science 2014 -, 2014
DOI:10.1155/2014/102946
View abstract

Chowdhury MR, Fester V, Kale G, Cespedes O Hydrothermal precipitation of beta-FeOOH nanostructure(s) in mixed solvent: study of their morphological and structural evolution JOURNAL OF NANOPARTICLE RESEARCH 16 -, 2014
DOI:10.1007/s11051-014-2412-4

Kulak AN, Semsarilar M, Kim YY, Ihli J, Fielding LA, Cespedes O, Armes SP, Meldrum FC One-pot synthesis of an inorganic heterostructure: Uniform occlusion of magnetite nanoparticles within calcite single crystals Chemical Science 5 738-743, 2014
DOI:10.1039/c3sc52615a
View abstract

Kim YY, Schenk AS, Walsh D, Kulak AN, Cespedes O, Meldrum FC Bio-inspired formation of functional calcite/metal oxide nanoparticle composites. Nanoscale 6 852-859, 2014
DOI:10.1039/c3nr05081e
View abstract

Moorsom T, Wheeler M, Taukeer Khan M, Al Ma'Mari F, Burnell G, Hickey BJ, Lazarov V, Gilks D, Cespedes O Effects of spin doping and spin injection in the luminescence and vibrational spectrum of C60 Applied Physics Letters 105 -, 2014
DOI:10.1063/1.4885336
View abstract

Gilks D, Lari L, Naughton J, Cespedes O, Cai Z, Gerber A, Thompson SM, Ziemer K, Lazarov VK Origin of anomalous magnetite properties in crystallographic matched heterostructures: Fe3O4(111)/MgAl2O4(111) Journal of Physics Condensed Matter 25 -, 2013
DOI:10.1088/0953-8984/25/48/485004
View abstract

Zhang Y, Pilapong C, Guo Y, Ling Z, Cespedes O, Quirke P, Zhou DJ Sensitive, Simultaneous Quantitation of Two Unlabeled DNA Targets Using a Magnetic Nanoparticle-Enzyme Sandwich Assay Analytical Chemistry -, 2013
View abstract

Gilks D, Lari L, Cai Z, Cespedes O, Gerber A, Thompson S, Ziemer K, Lazarov VK Magnetism and magnetotransport in symmetry matched spinels: Fe3O4/MgAl2O4 Journal of Applied Physics 113 -, 2013
DOI:10.1063/1.4800690
View abstract

Wheeler M, Hickey BJ, Cespedes O Enhanced exchange bias of spin valves fabricated on fullerene-based seed layers IEEE Transactions on Magnetics 48 3047-3050, 2012
DOI:10.1109/TMAG.2012.2198200
View abstract

Aljabali AAA, Barclay JE, Cespedes O, Rashid A, Staniland SS, Lomonossoff GP, Evans DJ Charge Modified Cowpea Mosaic Virus Particles for Templated Mineralization ADVANCED FUNCTIONAL MATERIALS 21 4137-4142, 2011
DOI:10.1002/adfm.201101048

Garcia J, Zhang Y, Taylor H, Cespedes O, Webb WE, Zhou DJ Multilayer enzyme-coupled magnetic nanoparticles as efficient, reusable biocatalysts and biosensors Nanoscale 3 3721-3730, 2011
DOI:10.1039/C1NR10411J
View abstract

Céspedes O, Inomoto O, Kai S, Nibu Y, Yamaguchi T, Sakamoto N, Akune T, Inoue M, Kiss T, Ueno S Radio frequency magnetic field effects on molecular dynamics and iron uptake in cage proteins. Bioelectromagnetics 31 311-317, 2010
DOI:10.1002/bem.20564
View abstract

Cespedes O, Inomoto O, Kai S, Ueno S Effects of Cationization and 6-Hydroxydopamine on the Reduced Iron Release Rates From Ferritin by Radio-Frequency Magnetic Fields, 2009
DOI:10.1109/TMAG.2009.2025048

Céspedes O, Ueno S Effects of radio frequency magnetic fields on iron release from cage proteins. Bioelectromagnetics 30 336-342, 2009
DOI:10.1002/bem.20488
View abstract

Cespedes O, Viret M Normal and reversed tunable magnetoresistance in a NiOx/p-doped silicon diode APPL PHYS LETT 94 -, 2009
DOI:10.1063/1.3070519

Cespedes O, Luu A, Rhen FMF, Coey JMD Fabrication of Magnetic Force Microscopy Tips via Electrodeposition and Focused Ion Beam Milling, 2008
DOI:10.1109/TMAG.2008.2002866

Cespedes O, Viret M, Coey JMD Magnetoresistance in NiOx nanoconstrictions controlled by magnetic fields and currents J APPL PHYS 103 -, 2008
DOI:10.1063/1.2904859

Cespedes O, Watts SM, Coey JMD, Dorr K, Ziese M Magnetoresistance and electrical hysteresis in stable half-metallic La0.7Sr0.3MnO3 and Fe3O4 nanoconstrictions APPL PHYS LETT 87 -, 2005
DOI:10.1063/1.2011770

Cespedes O, Clifford E, Coey JMD Spin polarization of Nb/Ni nanocontacts measured by Andreev reflection in planar thin-film geometry, 2005
DOI:10.1016/j.jmmm.2004.11.225

Cespedes O, Clifford E, Coey JMD Magnetoresistance of magnetite point contacts and nanoconstrictions J APPL PHYS 97 -, 2005
DOI:10.1063/1.1853497

Cespedes O, Rocha AR, Lioret S, Viret M, Dennis C, Gregg JF, van Dijken S, Sanvito S, Coey JMD I-V asymmetry and magnetoresistance in nickel nanoconstrictions, 2004
DOI:10.1016/j.jmmm.2003.12.293

Cespedes O, Ferreira MS, Sanvito S, Kociak M, Coey JMD Contact induced magnetism in carbon nanotubes J PHYS-CONDENS MAT 16 L155-L161, 2004
DOI:10.1088/0953-8984/16/10/L06

Cespedes O, Jan G, Viret M, Bari M, Coey JMD Random telegraph noise in a nickel nanoconstriction J APPL PHYS 93 8433-8435, 2003
DOI:10.1063/1.1556981

Jan G, Cespedes O, Fitzgerald C, Bari M, Coey JMD Noise in thin half-metallic oxide films Digests of the Intermag Conference -, 2002
View abstract

Raquet B, Broto JM, Viret A, Sondergard E, Cespedes O Electronic scattering and spin disorder in 3d-ferromagnets in the paraprocess regime, 2002

Raquet B, Viret M, Sondergard E, Cespedes O, Mamy R Electron-magnon scattering and magnetic resistivity in 3d ferromagnets PHYS REV B 66 -, 2002
DOI:10.1103/PhysRevB.66.024433

Raquet B, Viret M, Broto JM, Sondergard E, Cespedes O, Mamy R Magnetic resistivity and electron-magnon scattering in 3d ferromagnets, 2002
DOI:10.1063/1.1456434

Cespedes O, Bari MA, Dennis C, Versluijs JJ, Jan G, O'Sullivan J, Gregg JF, Coey JMD Fabrication and characterisation of Ni nanocontacts, 2002