Magnetic Effects at Surfaces and Interfaces (Including Grain Boundaries)
- PDF / 771,462 Bytes
- 12 Pages / 414.72 x 648 pts Page_size
- 47 Downloads / 230 Views
Department of Physics & Astronomy, Northwestern University, Evanston, IL 60208 of Physics & Astronomy, California State University, Northridge, CA 91330
** Department
ABSTRACT First-principles electronic structure studies based on local spin density functional theory and performed on extremely complex simulations of ever increasingly realistic systems, play a very important role in explaining and predicting surface and interface magnetism. This has led to solving even more challenging problems like the embrittlement of the Fe grain boundary, discussed here. Now, a major issue for first-principles theory is the treatment of the weak spin-orbit coupling (SOC) in magnetic transition metals and their alloys and its subsequent effects: (i) A major breakthrough in eliminating the numerical randomness for the determination of the magneto-crystalline anisotropy was made with the state-tracking and torque approaches. This now enables us to treat magnetostriction and its inverse effect, strain-induced magnetic anisotropy in transition metal bulk, thin films and alloys. (ii) The magneto-optical Kerr effects and x-ray magnetic circular dichroism are now directly calculated and compared with experiment. In all this work, and more recently, on the firstprinciples calculations of giant magneto-resistance in multilayers, extensive first-principles calculations and model analyses provide simple physical insights and guidelines to search for new magnetic recording and sensor materials. INTRODUCTION Magnetism research has been undergoing a renaissance over the last decade following the discovery of a variety of new scientific phenomena associated with man-made transition metal thin films. Among them are the theoretical prediction of enhanced magnetic moments in ultra-thin films and at surfaces [1,2], the discovery of perpendicular magnetic anisotropy [3] in ultra-thin films and layered structures, and the discovery of giant magnetoresistance (GMR) [4,5] and the accompanying oscillatory exchange coupling in multilayers made by alternating magnetic and "nonmagnetic" metals [6]. Some of these discoveries are already
having a major impact on the magnetic recording industry. An example is the so-called spinvalve sensor [7], which is about to be used as a magnetic recording head. Other applications are multilayers with out-of-plane anisotropy which show promise as "blue" magneto-optical media [8], or GMR based structures which offer non-volatile alternatives to semiconductor based DRAM [9]. The great success of first principles electronic structure studies based on local spin density functional theory, which performs extremely complex simulations of ever increasingly realistic systems, plays a very important role in explaining magnetism in thin films and has led to the facing of even more challenging problems [1]. Theoretical calculations predicted the large enhancement of the magnetic moment for 3d transition metal (TM) surfaces or overlayers deposited on inert substrates, and the possible magnetization in some normally non-magnetic ma
Data Loading...
