arXiv subjects

S. J. Blundell

Publications and source records attributed to S. J. Blundell.

114 records · Page 7Linked to original sources

arXiv2003

Angle Dependent Magnetoresistance of the Layered Organic Superconductor κ-(ET)2Cu(NCS)2: Simulation and Experiment

The angle-dependences of the magnetoresistance of two different isotopic substitutions (deuterated and undeuterated) of the layered organic superconductor κ-(ET)2Cu(NCS)2 are presented. The angle dependent magnetoresistance oscillations (AMRO) arising from the quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces in this material are often confused. By using the Boltzman transport equation extensive simulations of the AMRO are made that reveal the subtle differences between the different species of oscillation. No significant differences are observed in the electronic parameters derived from quantum oscillations and AMRO for the two isotopic substitutions. The interlayer transfer integrals are determined for both isotopic substitutions and a slight difference is observed which may account for the negative isotope effect previously reported [1]. The success of the semi-classical simulations suggests that non-Fermi liquid effects are not required to explain the interlayer-transport in this system.

cond-mat.str-el↗

arXiv2003

Spin freezing and magnetic inhomogeneities in bilayer manganites

We have performed a muon spin rotation study on polycrystalline samples of electron-doped layered manganites, La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (0.4< x<1), in order to investigate the local magnetic structure and spin dynamics. Our results provide evidence for phase separation into A-type antiferromagnetic and charge-ordered phases for x=0.52 and spin freezing at low temperatures (T<100K) for 0.52<x<0.75. A new phase diagram which includes this spin freezing region is proposed.

cond-mat.str-el↗

arXiv2002

Spin-polarized muons in condensed matter physics

A positive muon is a spin-1/2 particle. Beams of muons with all their spins polarized can be prepared and subsequently implanted in various types of condensed matter. The subsequent precession and relaxation of their spins can then be used to investigate a variety of static and dynamic effects in a sample and hence to deduce properties concerning magnetism, superconductivity and molecular dynamics. Though strictly a lepton, and behaving essentially like a heavy electron, it is convenient to think of a muon as a light proton, and it is often found with a captured electron in a hydrogen-like atom known as muonium. This article outlines the principles of various experimental techniques which involve implanted muons and describes some recent applications. The use of muons in condensed matter physics has shed new light on subjects as diverse as passivation in semiconductors, frustrated spin systems, vortex lattice melting, and quantum diffusion of light particles.

cond-mat.str-el↗

arXiv2002

The Hydride Anion in an Extended Transition Metal Oxide Array: LaSrCoO_3H_{0.7}

We present the synthesis and structural characterisation of a transition metal oxide hydride, LaSrCoO_3H_{0.7}, which adopts an unprecedented structure in which oxide chains are bridged by hydride anions to form a two- dimensional extended network. The metal centers are strongly coupled by their bonding with both oxide and hydride ligands to produce magnetic ordering up to at least 350 K. The synthetic route is sufficiently general to allow the prediction of a new class of transition metal-containing electronic and magnetic materials.

cond-mat.str-el↗

arXiv2001

Magneto-optics of organic crystalline field effect transistors

Organic molecular FETs provide an experimental framework for studying the band-filling dependent properties of two-dimensional metals. Here, we propose experiments to investigate the band-filling dependent cyclotron resonance, and the effect of van Hove singularities.

cond-mat↗

arXiv2001

Test for interlayer coherence in a quasi-two-dimensional superconductor

Peaks in the magnetoresistivity of the layered superconductor $κ$-(BEDT-TTF)$_2$Cu(NCS)$_2$, measured in fields $\leq 45$ T applied within the layers, show that the Fermi surface is extended in the interlayer direction and enable the interlayer transfer integral ($t_{\perp} \approx 0.04$ meV) to be deduced. However, the quasiparticle scattering rate $τ^{-1}$ is such that $\hbar/τ\sim 6t_{\perp}$, implying that $κ$-(BEDT-TTF)$_2$Cu(NCS)$_2$ meets the criterion used to identify interlayer incoherence. The applicability of this criterion to anisotropic materials is thus shown to be questionable.

cond-mat.str-el↗