Muons and magnets

Abstract:

Electronic and magnetic properties of the charge ordered phase of LuFe2 O4 are investigated by means of x-ray spectroscopic and theoretical electronic structure approaches. LuFe2 O4 is a compound showing fascinating magnetoelectric coupling via charge ordering. Here, we identify the spin ground state of LuFe2 O4 in the charge ordered phase to be a 2:1 ferrimagnetic configuration, ruling out a frustrated magnetic state. An enhanced orbital moment may enhance the magnetoelectric coupling. Furthermore, we determine the densities of states and the corresponding correlation potentials by means of x-ray photoelectron and emission spectroscopies, as well as electronic structure calculations. © 2009 The American Physical Society.

Abstract:

The slight incommensurate modulation of the structure of Bi(2)Mn(4/3)Ni(2/3)O(6) is sufficient to suppress the electrical polarization which arises in commensurate treatments of the structure, due to antiferroelectric coupling of local polar units of over 900 A(3). The incommensurate structure is produced by the competition between ferroelectric Bi lone pair-driven A site displacement, chemical order of Mn and Ni on the B site, and both charge and orbital order at these transition metals. The interplay between the frustrated polar Bi displacements and the frustrated spin order at the B site, induced by positional disorder, produces magnetodielectric coupling between the incommensurately modulated lattice and the spin-glass-like ground state with an unusual relationship between the magnetocapacitance and the applied field.

Abstract:

Abstract An understanding of thermal physics is crucial to much of modern physics, chemistry, and engineering. This book provides a modern introduction to the main principles that are foundational to thermal physics, thermodynamics, and statistical mechanics. The key concepts are carefully presented in a clear way, and new ideas are illustrated with worked examples as well as a description of the historical background to their discovery. Applications are presented to subjects as diverse as stellar astrophysics, information and communication theory, condensed matter physics, and climate change. Each chapter concludes with detailed exercises. This second edition of the text maintains the structure and style of the first edition but extends its coverage of thermodynamics and statistical mechanics to include several new topics, including osmosis, diffusion problems, Bayes theorem, radiative transfer, the Ising model, and Monte Carlo methods. New examples and exercises have been added throughout.