Perpendicular-Current Spin-Polarized Transport Studies

Michigan State University, East Lansing MI

Investigators

Abstract

This program involves two related projects with potential applications in the computer industry. A team of researchers at the Michigan State University (MSU) will investigate and manipulate the magnetic properties of alternating ferromagnetic and nonmagnetic metal layers. In the first project, precision measurements of the specific resistance, a quantity equal to the product of the sample area and its electrical resistance, of interfaces between carefully chosen pairs of metals will be made. Comparison of these results with calculations will test our current understanding of the electronic transport in magnetic multilayers, thereby providing the basis for future technological designs. The second project deals with current-induced magnetization switching in metallic magnetic multilayers. This study is of great interest both for writing magnetic random access memory and as a possible source of unwanted noise in potential new generation read-heads. To test predictions, the MSU group will measure how both the switching current and the magnetoresistance vary with many different combinations of magnetic and non-magnetic metal layers, prepared using their versatile nano-fabrication facilities. By participating in this project, graduate and undergraduate students will gain experience in planning and carrying out cutting-edge scientific research. The program also involves collaborations with scientists in France and Holland. Until recently, it was assumed that reversal of magnetization in magnetic layers, needed for information storage in computers, could be effected by applying an external magnetic field. A team of researchers at the Michigan State University has helped to show that passing a large enough current in the direction perpendicular to the multilayer can induce magnetization switching. In order to achieve this, the lateral dimensions of the multilayer need to be less than one micrometer, which requires modern "nanofabrication" techniques. The proposed research will study different combinations of magnetic and non-magnetic metal multilayers to understand the physics underlying current-induced magnetization switching. The research team will make precision measurements of the electrical and magnetic properties of the interfaces between carefully chosen pairs of metals. Comparison of these measurements with calculations will test our fundamental understanding of electronic transport in magnetic multilayers, thereby providing the basis for technological design. These projects could lead to new devices for use in computer hard disks. By participating in this project, graduate and undergraduate students will gain experience in planning and carrying out cutting-edge scientific research that directly relates to technological progress. The program also involves collaborations with scientists in other countries.