Noncollinear Magnetism

Recently, a great deal of effort has been focused on developing the so called “fully unconstrained” approach to noncollinear magnetism. This approach allows the magnetization density within a material to be calculated as a continuous vector variable of position, as opposed to using the atomic moment approximation (AMA) where a fixed quantization direction is assumed for a volumefilling sphere surrounding each atomic site, i.e., the constrained approach. In this paper a number of applications of the method are reviewed. Initially, only small clusters of Iron (Fe) and Chromium (Cr) atoms were studied which nicely illustrated some possible noncollinear magnetic arrangements. However, later research has been applied to triangular free-standing Cr and Manganese (Mn) monolayers and overlayers on Cu substrates. Finally, noncollinear magnetism has been investigated within the different phases of Mn, including the complex α-Mn phase, which has been shown experimentally to have a noncollinear magnetic structure.