Showing 184 results for Author: Andrew D. Christianson
Dec, 2008
Journal
The cascade of temperature and field-driven transitions in LuFeO was investigated byM�Nossbauer and optical spectroscopies, magnetization, and x-ray scattering. A correlation of Fe2+ ��Fe3+ charge transfer excitations with the 320 K phase transition below which uperstructure reflections appear confirms its association with gradual charge carrier freezing. Fe2+ on-site exci…
Dec, 2008
Journal
Pr3In exhibits an antiferromagnetic transition at ~12 K. This transition appears to occur due to the exchange-generated admixture of higher lying crystal field levels into the singlet ground state. It is thus an example of an induced moment antiferromagnet. To provide detailed understanding of the magnetic behavior of Pr3In we have measured the magnetic excitation spectrum…
Sep, 2008
Journal
We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of ``FeAs'' based oxypnictide superconductors. Upon cooling this material undergoes a tetragonal-orthorhombic crystallographic phase transition at ~160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperatu…