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Instruments / Technical Area	Publication Details	Published
I06-Nanoscience	Voltage-driven displacement of magnetic vortex cores M. Ghidini , R. Pellicelli , R. Mansell , D. Pesquera , B. Nair , X. Moya , S. Farokhipoor , F. Maccherozzi , C. H. W. Barnes , R. P. Cowburn , S. S. Dhesi , N. D. Mathur Journal Of Physics D: Applied Physics 53 DOI: 10.1088/1361-6463/aba01d Diamond Proposal Number(s): [11843] Open Access Show Abstract ▼ Abstract: Magnetic vortex cores in polycrystalline Ni discs underwent non-volatile displacements due to voltage-driven ferroelectric domain switching in single-crystal BaTiO3. This behaviour was observed using photoemission electron microscopy to image both the ferromagnetism and ferroelectricity, while varying in-plane sample orientation. The resulting vector maps of disc magnetization match well with micromagnetic simulations, which show that the vortex core is translated by the transit of a ferroelectric domain wall, and thus the inhomogeneous strain with which it is associated. The non-volatility is attributed to pinning inside the discs. Voltage-driven displacement of magnetic vortex cores is novel, and opens the way for studying voltage-driven vortex dynamics.	Oct 2020
I10-Beamline for Advanced Dichroism	Etching induced formation of interfacial FeMn in IrMn/CoFe bilayers D. O’donnell , S. Hassan , Y. Du , N. Gauquelin , D Krishnan , J. Verbeeck , R. Fan , P. Steadman , P. Bencok , A. N. Dobrynin Journal Of Physics D: Applied Physics 52 DOI: 10.1088/1361-6463/ab03bd Show Abstract ▼ Abstract: The effect of ion etching on exchange bias in IrMn3/Co70Fe30 bilayers is investigated. In spite of the reduction of saturation magnetization caused by the embedding of Ir from the capping layer into the Co70Fe30 layer during the etching process, the exchange bias in samples with the same thickness of the Co70Fe30 layer is reducing in proportion to the etching power. X-ray magnetic circular dichroism measurements revealed the emergence of an uncompensated Mn magnetization after etching, which is antiferromagnetically coupled to the ferromagnetic layer. This suggests etching induced formation of small interfacial FeMn regions which leads to the decrease of effective exchange coupling between ferromagnetic and antiferromagnetic layers.	Apr 2019
I06-Nanoscience	Voltage control of magnetic single domains in Ni discs on ferroelectric BaTiO3 Massimo Ghidini , Bonan Zhu , Rhodri Mansell , Raffaele Pellicelli , Arnaud Lesaine , Xavier Moya , Sam Crossley , Bhasi Nair , Francesco Maccherozzi , Crispin H. W. Barnes , Russell P. Cowburn , Sarnjeet Dhesi , Neil D. Mathur Journal Of Physics D: Applied Physics 51, 22 DOI: 10.1088/1361-6463/aabf77 Diamond Proposal Number(s): [9590] Show Abstract ▼ Abstract: For 1 microm-diameter Ni discs on a BaTiO3 substrate, the local magnetization direction is determined by ferroelectric domain orientation as a consequence of growth strain, such that single-domain discs lie on single ferroelectric domains. On applying a voltage across the substrate, ferroelectric domain switching yields non-volatile magnetization rotations of 90°, while piezoelectric effects that are small and continuous yield non-volatile magnetization reversals that are non-deterministic. This demonstration of magnetization reversal without ferroelectric domain switching implies reduced fatigue, and therefore represents a step towards applications.	May 2018
I10-Beamline for Advanced Dichroism	Tailoring the interfacial exchange coupling of perpendicularly magnetized Co/ L 1 0 -Mn 1.5 Ga bilayers J. X. Xiao , J. Lu , W. Q. Liu , Y. W. Zhang , H. L. Wang , L. J. Zhu , H. X. Deng , D. H. Wei , Y. B. Xu , J. H. Zhao Journal Of Physics D: Applied Physics 49 DOI: 10.1088/0022-3727/49/24/245003 Show Abstract ▼ Abstract: We have studied the magnetic properties of Co (2–12 MLs)/L10-Mn1.5Ga (15 nm) bilayers without and with annealing at 300 °C by a combination of superconducting quantum interference device (SQUID) magnetometry and x-ray magnetic circular dichroism (XMCD). We find that the Co layer can remain perpendicularly magnetized when its thickness is less than six monolayers due to the coupling between Co and L10-Mn1.5Ga layers, which is doubly confirmed by both SQUID and XMCD measurements. Such an exchange coupling between L10-Mn1.5Ga and Co layers changes from ferromagnetic coupling to antiferromagnetic coupling after the annealing process. Furthermore, the magnetic coupling can also be tailored from ferromagnetic to antiferromagnetic by changing the L10-Mn1.5Ga surface from Mn-rich to Ga-rich. The first-principles calculations show that the interfacial coupling type is ferromagnetic for a Mn-terminated L10-Mn1.5Ga bilayer, while antiferromagnetic for a Ga-terminated bilayer. The spin and orbital moments of Co in the Co/L10-Mn1.5Ga bilayers are calculated according to the sum rules and the ratio of the orbital to spin magnetic moments for Co is not enhanced like other perpendicularly magnetized Co-based multilayers such as Co/Pd and Co/Pt.	Jun 2016
	Charge transport optimization in CZT ring-drift detectors V. Boothman , A. Alruhaili , V. Perumal , P. Sellin , A. Lohstroh , K. Sawhney , S. Kachanov Journal Of Physics D: Applied Physics 48 DOI: 10.1088/0022-3727/48/48/485101 Show Abstract ▼ Abstract: Ring-drift design has been applied to large (7.5mm×7.5mm×2.3 mm) cadmium zinc telluride (CZT) devices. This low-noise, single-carrier-sensing configuration is the gold standard for spectroscopic silicon x-ray detectors. By combining the advantages of ringdrift with the high quantum efficiency and room-temperature operating capabilities of CZT, a simple and compact device for high-resolution spectroscopy of x-rays in the range 50–500 keV can be created. Quality of CZT crystals has improved greatly in recent years and electron-only sensing overcomes the problem of inherently poor hole transport in II–VI semiconductors. The spatial response of our 3-ring CZT device was studied by microbeam scanning while the voltages applied to all electrodes were systematically varied. Maximum active radius extended to 2.3 mm, beyond the second ring. Resolution was limited by electronic noise. Our results show that the lateral field and its ratio to the bulk field exert a crucial influence on active area, peak position and sensitivity. CZT and the device geometry were modelled in 3D with Sentaurus TCAD. Line scans were simulated and trends in performance with bias conditions matched experimental data, validating the model. We aimed to optimize the resolution, sensitivity and active radius of the device. Fields and charge drift were visualized and the active volume was mapped in 3D to improve understanding of the factors governing performance including number of rings, their widths, positions and bias.	Dec 2015
	Microscopic origin of the reduced magnetocrystalline anisotropy with increasing oxide content in Co80Pt20:oxide thin films Wen Zhang , Simon A Morton , P K Johnny Wong , Bin Lu , Yongbing Xu , Michel P De Jong , Wilfred G Van Der Wiel , Gerrit Van Der Laan Journal Of Physics D: Applied Physics 46 (40), 405001 DOI: 10.1088/0022-3727/46/40/405001 Show Abstract ▼ Abstract: Angle-dependent x-ray magnetic circular dichroism at the Co L2.3 edges has been utilized to systematically study Co80Pt20 :WO3 perpendicular magnetic recording thin films, in which the magnetocrystalline anisotropy significantly drops as the oxide volume fraction increases. The microscopic origin of this phenomenon in the studied films can be mainly attributed to an increase in orbital moment normal to the grainoxide interface, with increasing oxide volume fraction, which arises from a more pronounced effect of symmetry breaking at the grainoxide interface in smaller grains.	Oct 2013
	Low-dimensional systems investigated by x-ray absorption spectroscopy: a selection of 2D, 1D and 0D cases Lorenzo Mino , Giovanni Agostini , Elisa Borfecchia , Diego Gianolio , Andrea Piovano , Erik Gallo , Carlo Lamberti Journal Of Physics D: Applied Physics 46 DOI: 10.1088/0022-3727/46/42/423001 Show Abstract ▼ Abstract: Over the last three decades low-dimensional systems have attracted increasing interest both from the fundamental and technological points of view due to their unique physical and chemical properties. X-ray absorption spectroscopy (XAS) is a powerful tool for the characterization of such kinds of systems, owing to its chemical selectivity and high sensitivity in interatomic distance determination. Moreover, XAS does not require long-range ordering, that is usually absent in low-dimensional systems. Finally, this technique can simultaneously provide information on electronic and local structural properties of the nanomaterials, significantly contributing to clarify the relation between their atomic structure and their peculiar physical properties. This review provides a general introduction to XAS, discussing the basic theory of the technique, the most used detection modes, the related experimental setups and some complementary relevant characterization techniques (diffraction anomalous fine structure, extended energy-loss fine structure, pair distribution function, x-ray emission spectroscopy, high-energy resolution fluorescence detected XAS and x-ray Raman scattering). Subsequently, a selection of significant applications of XAS to two-, one- and zero-dimensional systems will be presented. The selected low-dimensional systems include IV and III–V semiconductor films, quantum wells, quantum wires and quantum dots; carbon-based nanomaterials (epitaxial graphene and carbon nanotubes); metal oxide films, nanowires, nanorods and nanocrystals; metal nanoparticles. Finally, the future perspectives for the application of XAS to nanostructures are discussed.	Oct 2013
I06-Nanoscience	Low-temperature transverse magnetic domains in nominally uniaxial La0.67Sr0.33MnO3 films on NdGaO3 (0 0 1) Lee Phillips , Massimo Ghidini , Xavier Moya , Francesco Maccherozzi , Sarnjeet Dhesi , Neil Mathur Journal Of Physics D: Applied Physics 46 (3) DOI: 10.1088/0022-3727/46/3/032002 Show Abstract ▼ Abstract: Epitaxial La0.67Sr0.33MnO3 films grown on orthorhombic NdGaO3 (0?0?1) substrates show predominantly uniaxial magnetic anisotropy. On cooling, we observe the growth of a biaxial contribution, which we quantify by fitting magnetometry data to a coherent rotation model. A film grown under deliberately sub-optimal conditions shows a relatively stronger biaxial contribution that results in a significant population of transverse magnetic domains below ~200 K, as revealed by photoemission electron microscopy with x-ray magnetic circular dichroism contrast. Care should be taken to avoid these transverse domains in spintronic devices designed to exploit the high low-temperature spin-polarization of La0.67Sr0.33MnO3.	Dec 2012
B22-Multimode InfraRed imaging And Microspectroscopy	Thermal evaporation and x-ray photostability of dodecyl-passivated silicon nanoparticles Paul Coxon , Shane Ashby , Mark Frogley , Yimin Chao Journal Of Physics D: Applied Physics 45 (35) DOI: 10.1088/0022-3727/45/35/355303 Diamond Proposal Number(s): [7065] Show Abstract ▼ Abstract: X-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy have been used to study the makeup of thin films of 6.5 nm diameter dodecyl-capped silicon nanoparticles (SiNPs) formed in a one-pot synthesis method of micelle reduction. Thermostability measurements show the SiNPs undergo thermal desorption at ~240 °C, a higher temperature than for SiNPs capped by shorter hydrocarbon layers owing to the greater size of the nanoparticle system in this case. Suspensions of SiNPs are found to evaporate in a UHV environment intact with the hydrocarbon passivating layer preserved and form thin films which are visualized with microimaging FTIR spectroscopy. The stability of the capping layer within thick SiNP films under extended exposure (up to 2160 s) to 140 eV photons has been examined where XPS spectra show the breakdown of the passivating layer allowing the underlying silicon core to undergo subsequent oxidation.	Sep 2012

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