The Nanoscience Beamline (I06) at Diamond Light Source

Dhesi, S. S.; Cavill, S. A.; Potenza, A.; Marchetto, Helder; Mott, RB; Steadman, P.; Peach, Andrew; Shepherd, E. L.; Ren, Xueming; Wagner, U.; Reininger, R.; Garrett, R.; Gentle, Ian R.; Nugent, Keith A.; Wilkins, S.

doi:10.1063/1.3463198

Cited by 22 publications

(16 citation statements)

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“…For the ME coupling measurements a voltage, V, was applied across the film and substrate with changes to the magnetization, measured 50 times each 1 second apart by VSM, recorded as a function of V. The reported change is an average of the last 40 measurements after it reaches . Ti L2,3 xray absorption spectroscopy (XAS), Co L2,3 and Fe L2,3 XAS and x-ray magnetic circular dichroism (XMCD) measurements were performed on beamline I06 at the Diamond Light Source [14]. Total-electron yield (TEY) was monitored using the sample drain current.…”

Section: Methodsmentioning

confidence: 99%

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Beevers

Love

Lazarov

et al. 2018

Applied Physics Letters

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Article:Beevers, J. E., Love, C. J., Lazarov, V. K. orcid.org/0000-0002-4314-6865 et al. The magnetoelectric effect in M-type Ti-Co doped strontium hexaferrite has been studied using a combination of magnetometry and element specific soft X-ray spectroscopies. A large increase (> x30) in the magnetoelectric coefficient is found when Co 2+ enters the trigonal bi-pyramidal site. The 5-fold trigonal bi-pyramidal site has been shown to provide an unusual mechanism for electric polarization based on the displacement of magnetic transition metal (TM) ions. For Co entering this site, an offcentre displacement of the cation may induce a large local electric dipole as well as providing an increased magnetostriction enhancing the magnetoelectric effect. INTRODUCTIONThe control of magnetism using applied electric fields offer the possibility of a new generation of ultralow power, high density storage. In this respect, magnetoelectric (ME) multiferroic materials are intensely studied in order to understand how different symmetry breaking orders exist in the same material and how these orders can be coupled. Among the few room temperature single-phase ME multiferroics reported, hexaferrites show potential for device applications as they exhibit a low field ME effect at room temperature [1]. M-type hexaferrites are arranged in different repeating sequences of basic building blocks; the R and S layers [2]. Fe 3+ cations occupy both octahedral (Oh) and tetrahedral (Td) co-ordinated sites in the S block (Wyckoff positions 2a and 4f1) and octahedral sites (12k and 4f2) in the R block, see online supplementary materials. The Ba ion located at positions 2d strongly distorts the octahedral site located at the 2b positions giving rise to a bi-pyramidal 5 fold co-ordination which induces a large uniaxial magnetic anisotropy parallel to the c-axis [3]. However, Co 2+ and Ti 4+ substitutions for Fe 3+ dramatically alters the magnetic properties [4]. Ti substitutions at the 12k sites decrease the exchange coupling between spins in the R and S blocks whilst Co substitutions change the magnetic anisotropy from uniaxial to an easy cone of magnetization tilted away from the c-axis. The result is to stabilize a non-collinear conical magnetic structure [2,5] which is of high interest in the field of multiferroics [6]. The ME effect at room temperature in SrFe8Ti2Co2O19 was first reported in bulk [7] and, thereafter, in thin films [8]. Co 2+ substitutions in ferrite structures are a well-known source of magnetoelastic coupling due to the large orbital moment of Co 2+ [9]. The linear ME coupling, , which is the change in magnetization with an applied electric field is directly proportional to the magnetoelastic coupling, or magnetostriction, , implying that an increase in  increases  [10]. However, a mechanism such as the piezoelectric effect or electrostriction for coupling the applied electric field into strain is also required. Several mechanisms for magnetically induced ferroelectricity have been proposed in recent years [11] with the sp...

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Section: Methodsmentioning

confidence: 99%

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Beevers

Love

Lazarov

et al. 2018

Applied Physics Letters

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“…Spatially resolved NEXAFS (μ-NEXAFS) measurements were performed at the Diamond Light Source, using the I06-Nanoscience soft X-ray beamline (30). The end station is an Elmitec LEEM III spectroscopic photoemission and low-energy electron microscope.…”

Section: Methodsmentioning

confidence: 99%

Influence of support morphology on the bonding of molecules to nanoparticles

Yim

Pang

Hermoso

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Supported metal nanoparticles form the basis of heterogeneous catalysts. Above a certain nanoparticle size, it is generally assumed that adsorbates bond in an identical fashion as on a semiinfinite crystal. This assumption has allowed the database on metal single crystals accumulated over the past 40 years to be used to model heterogeneous catalysts. Using a surface science approach to CO adsorption on supported Pd nanoparticles, we show that this assumption may be flawed. Near-edge X-ray absorption fine structure measurements, isolated to one nanoparticle, show that CO bonds upright on the nanoparticle top facets as expected from single-crystal data. However, the CO lateral registry differs from the single crystal. Our calculations indicate that this is caused by the strain on the nanoparticle, induced by carpet growth across the substrate step edges. This strain also weakens the COmetal bond, which will reduce the energy barrier for catalytic reactions, including CO oxidation.nanoparticle | carpet growth | surface strain | adsorption | scanning tunneling microscopy N anoparticles exhibit properties distinct from their bulk counterparts (1-3). For instance, semiconductor particles smaller than ∼10 nm act as quantum dots (1-4) and oxide-supported gold nanoparticles are active for a variety of reactions including CO oxidation (5), water-gas-shift reaction (6), and epoxidation (7), whereas gold itself is not. Nanoclusters composed of ∼10 atoms have been shown to be exceptionally catalytically active for some reactions on some metals (8, 9). When the particle size is reduced, the relative number of undercoordinated atoms at the edges and corners increases. The proportion of perimeter sites at the interface between the metal and the support also increases. All these sites have been shown to play a crucial role in some reactions (10, 11). Reducing the particle size can also lead to a decrease in the interatomic bond length in small metal clusters (12, 13), which in the case of Pd nanoparticles results in lower adsorption energies for both CO (14,15) and O 2 (16), although such weakening of CO binding on the nanoparticle can also arise from other factors such as encapsulation of the nanoparticles by the support (17).The role of the support in modifying nanoparticle properties has also been recognized. For instance, the strong metal support interaction has been known for some time (2) and charge transfer either to or from the nanoparticles can lead to enhanced reactivity (18). More recently, it has come to light that the particle size itself may be governed by the interaction with the support (19). However, one effect that has not been discussed and yet should be present in any nanoparticle-support system is the influence of the support morphology such as steps.Here, we investigate the role of the support morphology on the reactivity of metal nanoparticles using scanning tunneling microscopy (STM). As our test system we choose Pd nanoparticles (20, 21) supported on TiO 2 (110) (22) simply because much is known about bo...

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“…In carbon K-edge NEXAFS measurements, the bonding orientation of CO on a surface can be probed by measuring the integrated intensity of the CO p* resonance peak (located at hm = 287 eV) as a function of either the angle of incidence, h (with the incident light oriented to be p-polarised) [11], or as a function of the direction of the electric field vector (E) of the incident photon beam, hence the polarization angle, b [26]. The former method gives I versus h curves while the latter method leads to I versus b curves.…”

Section: Resultsmentioning

confidence: 99%

Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

2016

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Near edge X-ray absorption fine structure (NEXAFS) measurements of CO on Pd nanoparticles have been simulated. This was achieved by calculating the CO p* resonance signal of CO on a nanoparticle both as a function of the angle of incidence (I vs h) and the direction of the electric field vector E of the incident photon beam (I vs b), with the nanoparticle defined as a 111 ð Þ top facet with 111 f g and 100 f g side facets. The dependence of the p* resonance intensity signal of CO covered nanoparticles on the particle geometry and orientation as well as the bond orientation of CO is examined. In addition, we compare our simulations to a set of C K-edge NEXAFS experimental data obtained from a single Pd nanoparticle decorated with CO. Our simulation predicts that the nanoparticle has a high lateral aspect ratio of 37.7 ± 4.1.

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The Nanoscience Beamline (I06) at Diamond Light Source

Cited by 22 publications

References 0 publications

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Enhanced magnetoelectric effect in M-type hexaferrites by Co substitution into trigonal bi-pyramidal sites

Influence of support morphology on the bonding of molecules to nanoparticles

Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

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