Biomedical subjects

MM Treacy

Publications and source records attributed to MM Treacy.

3 recordsLinked to original sources

PubMed2000

Holes in a Quantum Spin Liquid.

Magnetic neutron scattering provides evidence for nucleation of antiferromagnetic droplets around impurities in a doped nickel oxide-based quantum magnet. The undoped parent compound contains a spin liquid with a cooperative singlet ground state and a gap in the magnetic excitation spectrum. Calcium doping creates excitations below the gap with an incommensurate structure factor. We show that weakly interacting antiferromagnetic droplets with a central phase shift of pi and a size controlled by the correlation length of the quantum liquid can account for the data. The experiment provides a quantitative impression of the magnetic polarization cloud associated with holes in a doped transition metal oxide.

Journal Article↗

PubMed2000

Atom pair persistence in disordered materials from fluctuation microscopy

We show that the kinematical theory of fluctuation microscopy for a disordered specimen can be reformulated in terms of an atom pair-pair correlation function. Resolution and coherence are two experimental variables which yield a two-dimensional fluctuation map. This map is a transformation of the pair-pair correlation function, but can be directly interpreted in terms of a pair persistence function (PPF). We show that the PPF reveals the correlation length and structure for a simple paracrystalline model.

Journal Article↗

PubMed2000

Fluctuation microscopy: a probe of atomic correlations in disordered materials

Fluctuation microscopy is a new technique to study medium-range structure in disordered materials. Low-resolution dark-field transmission electron microscope images are interpreted as spatially resolved diffraction maps. Statistical analysis of intensity variations in these maps provides information about higher-order atom position correlation functions. Here we give a qualitative description of the technique and explore the properties and utility of higher-order correlation functions in describing the structure of disordered materials.

Journal Article↗