Peter J. Baker

Bio: Peter J. Baker is an academic researcher from Rutherford Appleton Laboratory. The author has contributed to research in topics: Muon spin spectroscopy & Relaxation (NMR). The author has an hindex of 27, co-authored 147 publications receiving 3841 citations. Previous affiliations of Peter J. Baker include University of Oxford & European Synchrotron Radiation Facility.

Spin Waves and Revised Crystal Structure of Honeycomb Iridate Na2IrO3

Abstract: We report inelastic neutron scattering measurements on ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$, a candidate for the Kitaev spin model on the honeycomb lattice We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order The onset of long-range magnetic order below ${T}_{N}=153\text{ }\text{ }\mathrm{K}$ is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90\ifmmode^\circ\else\textdegree\fi{} Ir-O-Ir bonds required for dominant Kitaev exchange

Enhancement of the superconducting transition temperature of FeSe by intercalation of a molecular spacer layer

Abstract: Altering the composition of the spacer layers present in iron-based superconductors is one strategy for increasing the temperature below which they superconduct. Now, intercalating FeSe with molecular spacer layers is also shown to enhance the superconducting transition temperature.

Coexistence of static magnetism and superconductivity in SmFeAsO(1-x)F(x) as revealed by muon spin rotation.

Abstract: In non-conventional superconductors, the competition of magnetic order and superconductivity seems to be a key element for the origin of superconductivity. Investigation of the newly discovered iron-pnictides superconductors challenges this picture, showing a coexistence of superconductivity and magnetism.

Polymorphism control of superconductivity and magnetism in Cs 3 C 60 close to the Mott transition

Abstract: The crystal structure of a solid controls the interactions between the electronically active units and thus its electronic properties. In the high-temperature superconducting copper oxides, only one spatial arrangement of the electronically active Cu(2+) units-a two-dimensional square lattice-is available to study the competition between the cooperative electronic states of magnetic order and superconductivity. Crystals of the spherical molecular C(60)(3-) anion support both superconductivity and magnetism but can consist of fundamentally distinct three-dimensional arrangements of the anions. Superconductivity in the A(3)C(60) (A = alkali metal) fullerides has been exclusively associated with face-centred cubic (f.c.c.) packing of C(60)(3-) (refs 2, 3), but recently the most expanded (and thus having the highest superconducting transition temperature, T(c); ref. 4) composition Cs(3)C(60) has been isolated as a body-centred cubic (b.c.c.) packing, which supports both superconductivity and magnetic order. Here we isolate the f.c.c. polymorph of Cs(3)C(60) to show how the spatial arrangement of the electronically active units controls the competing superconducting and magnetic electronic ground states. Unlike all the other f.c.c. A(3)C(60) fullerides, f.c.c. Cs(3)C(60) is not a superconductor but a magnetic insulator at ambient pressure, and becomes superconducting under pressure. The magnetic ordering occurs at an order of magnitude lower temperature in the geometrically frustrated f.c.c. polymorph (Neel temperature T(N) = 2.2 K) than in the b.c.c.-based packing (T(N) = 46 K). The different lattice packings of C(60)(3-) change T(c) from 38 K in b.c.c. Cs(3)C(60) to 35 K in f.c.c. Cs(3)C(60) (the highest found in the f.c.c. A(3)C(60) family). The existence of two superconducting packings of the same electronically active unit reveals that T(c) scales universally in a structure-independent dome-like relationship with proximity to the Mott metal-insulator transition, which is governed by the role of electron correlations characteristic of high-temperature superconducting materials other than fullerides.

Recent advances in the synthesis and application of layered double hydroxide (LDH) nanosheets.

Abstract: Layered double hydroxides (LDHs) are a class of ionic lamellar compounds made up of positively charged brucite-like layers with an interlayer region containing charge compensating anions and solvation molecules. Delamination of LDHs is an interesting route for producing positively charged thin platelets with a thickness of a few atomic layers, which can be used as nanocomposites for polymers or as building units for making new designed organic-inorganic or inorganic-inorganic nanomaterials. The synthesis of nanosized LDH platelets can be generally classified into two approaches, bottom-up and top-down. It requires modification of the LDH interlamellar environment and then selection of an appropriate solvent system. In DDS intercalated LDHs, the aliphatic tails of the DDS- anions exhibit a high degree of interdigitation in order to maximize guest-guest dispersive interactions. Bellezza reported that the LDH colloids can also been obtained by employing a reverse microemulsion approach.

Magnetic metal-organic frameworks.

Abstract: The purpose of this critical review is to give a representative and comprehensive overview of the arising developments in the field of magnetic metal–organic frameworks, in particular those containing cobalt(II). We examine the diversity of magnetic exchange interactions between nearest-neighbour moment carriers, covering from dimers to oligomers and discuss their implications in infinite chains, layers and networks, having a variety of topologies. We progress to the different forms of short-range magnetic ordering, giving rise to single-molecule-magnets and single-chain-magnets, to long-range ordering of two- and three-dimensional networks (323 references).

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

Abstract: The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

Superconductivity in iron compounds

Abstract: Kamihara and coworkers' report of superconductivity at ${T}_{c}=26\text{ }\text{ }\mathrm{K}$ in fluorine-doped LaFeAsO inspired a worldwide effort to understand the nature of the superconductivity in this new class of compounds. These iron pnictide and chalcogenide (FePn/Ch) superconductors have Fe electrons at the Fermi surface, plus an unusual Fermiology that can change rapidly with doping, which lead to normal and superconducting state properties very different from those in standard electron-phonon coupled ``conventional'' superconductors. Clearly, superconductivity and magnetism or magnetic fluctuations are intimately related in the FePn/Ch, and even coexist in some. Open questions, including the superconducting nodal structure in a number of compounds, abound and are often dependent on improved sample quality for their solution. With ${T}_{c}$ values up to 56 K, the six distinct Fe-containing superconducting structures exhibit complex but often comparable behaviors. The search for correlations and explanations in this fascinating field of research would benefit from an organization of the large, seemingly disparate data set. This review provides an overview, using numerous references, with a focus on the materials and their superconductivity.