Correlation Between Magnetism, Structure and Growth for Ultrathin Fe Films on Cu(100)

Abstract

To obtain a comprehensive understanding of the correlation between the magnetism and structure of materials has been a research goal of scientists for a long time. Early in the 1930s, Bethe and Slater found a phenomenological relationship between the direct exchange interaction and the atomic separation [1, 2] (Fig. 6.1). This is the well known Bethe-Slater curve. Recently, the correlation between the structure and the magnetism for 3d metals has been investigated with advanced self-consistent energy-band calculations [4, 5, 6]. These calculations show that the magnetic properties of a 3d metal are closely related to the atomic volume. Normally magnetic transition metals will lose their magnetic moment at a compressed volume and, on the other hand, non-magnetic transition metals will become ferromagnetic at an expanded volume. Thus a transition from the nonmagnetic to a magnetic state is expected for all 3d transition metals when the atomic volume is increased. In the limit of large volume, the magnetic moment approaches the value determined by Hund's rule for the free-atom configuration. Three types of transition behavior , classified as type I, type II and type III depending on the number (one, two and three, respectively) of critical points, have been predicted (see Fig. 6.2). Bcc Sc, Ti, Fe, Co and Ni have been predicted to show a type I tran-Fig. 6.1. The Bethe-Slater curve relates the exchange constant J to the ratio of the atomic separation R to the radius of the d shell R d. From [3], used with permission