9701548 Schiffer This is a CAREER proposal on magnetic materials that are employed in all facets of modern technology from computer discs to automobile engines. In these materials, the magnetic moments (which can be thought of as microscopic quantum mechanical bar magnets) interact with each other, and the nature of the interactions has a profound impact on the material properties. The proposed research will investigate two classes of magnetic materials: geometrically frustrated magnets in which the geometrical placement of the magnetic moments results in a precisely balanced competition between interactions and colossal magnetoresistance manganites in which the interaction between the magnetic moments is closely tied the conduction of electrical current. The proposed educational initiative will be the development of a seminar course in modern condensed matter physics. Since standard condensed matter physics courses typically do not cover the developments of the past three decades, this course will give students a broad overview of research areas of current interest. %%% The proposed CAREER research will investigate the properties of novel magnetic materials at low temperatures. One subject of research will be geometrically frustrated magnets, in which the magnetic ions interact antiferromagnetically, but the interactions are frustrated by the lattice geometry. Thermodynamic measurements on these systems are planned as a function of magnetic field, temperature, and non-magnetic impurity concentration in order to elucidate their novel low temperature behavior. A second area of research will be investigations of the rare-earth manganites which have been recently shown to display large magnetoresistance. In particular the compositional phase diagrams of these materials will be examined to understand the observed transitions between various magnetic and electronic phases. The development of a new course in modern condensed matter physics is also planned. The intent of the course is to expose graduate students and advanced undergraduates to modern research topics (such as spin glasses, liquid helium, and high temperature superconductors) which are typically excluded from standard courses on condensed matter physics. ***
