Doping Dependent Transition from Paramagnetism to Ferromagnetism in Semiconductors

Louisiana State University, Baton Rouge LA

Investigators

Abstract

Non-technical abstract In order to accelerate the technological revolution that has placed high speed computation and information storage at our fingertips almost anywhere on Earth, new ideas are essential. One pathway for progress in semiconductor device design, known as spintronics, seeks to make use of the magnetic degrees of freedom to the same extent that charge degrees of freedom are used in present day silicon technologies. As scientists have sought to control or manipulate the electron spin, the intrinsic magnetic property of electrons, they have recognized the utility of materials that are both magnetic and semiconducting. However, of the small number of such systems presently known, none completely meet requirements such as compatibility with silicon, room temperature magnetism, and the possibility of coupling to electrical and optical signals that are necessary for spintronics technologies. As is true of many nascent technologies, fundamental explorations of material and physical properties can lead to breakthroughs. This project investigates a range of magnetic and semiconducting materials to explore the mechanisms for magnetism which includes the interaction of electronic and magnetic degrees of freedom and to document the ramifications of these interactions on the physical properties of these systems. Students on many levels, as well as high school teachers, will be exploring magnetic, electric, optical, and thermodynamic properties of these magnetic semiconductors in crystalline, thin film, and nanowire form. Technical abstract Although magnetic semiconductors have received enormous attention because of their potential use in spintronics devices, from a fundamental viewpoint they remain poorly explored. In particular, it has been very difficult to separate the often overwhelming defect related issues from the more interesting essential behaviors. This project will investigate a set of magnetic and semiconducting silicides and sulfides where careful characterization has demonstrated that secondary phases and defect related issues are not relevant. This control over materials properties allows access to a unique regime, that near the transition(s) from paramagnetic insulator to magnetic metal in a semiconductor by way of chemical substitution in crystals, thin films, and nanowires. Students on many levels, as well as high school teachers will be exploring these materials searching for novel transport, magnetic, thermodynamic, and optical properties that may, perhaps, be exploited in future technologies.