Despina Louca

Structural analysis of complex materials using the atomic pair distribution function — a practical guide

Abstract Modern materials and their properties are often characterized by varying degrees of disorder. Routine crystallographic structure solution only reveals the average structure. The study of Bragg and diffuse scattering yields the local atomic arrangements holding the key to understanding increasingly complex materials. In this paper we review the pair distribution function technique used to unravel the local structure. We aim to give a practical overview and make this method easily accessible to the wider scientific community.

Nanomagnetic droplets and implications to orbital ordering in La1-xSrxCoO3

Inelastic cold-neutron scattering on LaCoO3 provided evidence for a distinct low energy excitation at 0.6 meV coincident with the thermally induced magnetic transition. Coexisting strong ferromagnetic (FM) and weaker antiferromagnetic correlations that are dynamic follow the activation to the excited state, identified as the intermediate S = 1 spin triplet. This is indicative of dynamical orbital ordering favoring the observed magnetic interactions. With hole doping as in La(1-x)Sr(x)CoO3 , the FM correlations between Co spins become static and isotropically distributed due to the formation of FM droplets. The correlation length and condensation temperature of these droplets increase rapidly with metallicity due to the double exchange mechanism.

Orbital and spin chains in ZnV2O4

Our powder inelastic neutron scattering data indicate that ZnV2O4 is a system of spin chains that are three-dimensionally tangled in the cubic phase above 50 K due to randomly occupied t(2g) orbitals of V3+ (3d(2)) ions. Below 50 K in the tetragonal phase, the chains become straight due to antiferro-orbital ordering. This is evidenced by the characteristic wave vector dependence of the magnetic structure factor that changes from symmetric to asymmetric at the cubic-to-tetragonal transition.

Investigation of the Spin-glass Regime Between the Antiferromagnetic and Superconducting Phases in Fe1+ySexTe1−x

Using bulk magnetization along with elastic and inelastic neutron scattering techniques, we have investigated the phase diagram of Fe

Frustrated Magnetism and Cooperative Phase Transitions in Spinels

_{1+y}

Magnetic transition broadening and local lattice distortion in the negative thermal expansion antiperovskite Cu1−xSnxNMn3

Se

Structure and composition of the superconducting phase in alkali iron selenide K y Fe 1.6 + x Se 2

_{x}

In-plane Charge Fluctuations in Bismuth Sulfide Superconductors

Te

Possible Link of a Structurally Driven Spin Flip Transition and the Insulator-Metal Transition in the Perovskite La 1 − x Ba x CoO 3

_{1-x}

Compression-compression fatigue study on model metallic glass nanowires by molecular dynamics simulations

and the nature of magnetic correlations in three nonsuperconducting samples of Fe