OPTICAL AND MAGNETO-OPTICAL PROPERTIES OF RARE EARTH METALS AND COMPOUNDS

Abstract

Highly localized 4f electrons in rare earth metals (REMs) are responsible for the large magnetic moments as well as for the unique optical, electrical and magnetic properties. Optical properties of materials, in general, can be utilized in various applications such as reflectors, filters and X-ray masks where reflectors are used for construction of large mirrors for space-based, lightweight optical telescopes. All intermetallic semiconductors can be considered in a simple sense to act as filters, and masks are required in lithography, e.g. X-ray, electron-beam lithography. On the other hand, magneto-optical (MO) properties of materials are used in strong permanent magnets and storage devices. Optical measurements on rare earths started in early sixty's. However, the experimental investigation on the optical properties of REMs has lagged behind that on other metals, because of REM's high reactivity with the environment. On the theoretical front, theorists had to wait for performing theoretical calculations on optical and MO properties, till the computational techniques were available. There are many research groups that are working to study and understand the optical and MO properties of the rare earth compounds. For the last twenty years, the use and developments in the linear methods for solving the band structure problem have almost totally erased the limitations that are faced in the other contemporary techniques. The linearization originates from the APW method proposed by Slater (1964). Great progress of the APW methodology was achieved as the concept of linear methods, was introduced by Andersen, and first applied by Koelling and Arbman ii using a model potential within the muffin-tin approximation. The linearized APW (LAPW) method reconciled the linear-algebra formulation of the variational problem with the convergence properties of the original formulation and allowed a straight forward extension of the method to the treatment of crystal potentials of general shape. The treatment of the potential and charge density without shape approximation, and the implementation of the total energy calculation led to the development of full-potential linearized augmented planewave (FPLAPW) method.