Manganese Films on Cu(100) and Ni(100)

Abstract

In the previous chapter, a correlation between the structure, growth and magnetism was established for the workhorse of thin-film magnetism, Fe/Cu(100). In this chapter, our attention is turned to a less studied, but potentially equally rewarding system: Mn on Cu(100). To facilitate the discovery of systematic trends, Mn/Ni(100) has been studied for comparison. Bulk manganese has one of the richest varieties of crystallographic and magnetic phases known for metallic elements. This makes Mn an interesting candidate for epitaxial-growth studies, since different crystallographic and magnetic modifications might be stabilized on different substrates. Table 7.1 lists the phases for bulk Mn. As a function of temperature, four different modifications are observed. The complex cubic $\alpha$ phase is stable up to approximately 1000 K. This phase has 58 atoms in the unit cell and is characterized by hexatetrahedral building blocks with nearest-neighbor spacings that vary between 2.24 and 3.0 Å. While $\alpha$-Mn is antiferromagnetic below 100 K, the other phases are paramagnetic at the temperatures at which they exist. The complex cubic $\beta$ phase, with 20 atoms per unit cell, is stable between 1000 and 1368 K. The $\gamma$ and $\delta$ modifications are face-centered cubic and body-centered cubic with a nearest-neighbor spacing of 2.73 Å (at 1373 K) and 2.67 Å (at 1413 K), respectively. $\gamma$-Mn is stable between 1368 and 1406 K, while $\delta$-Mn is stable between 1406 and 1517 K.