Noncollinear magnetism in permalloy

Permalloy is an important material in a wide variety of magnetic systems, most notably in giant-magnetoresistive read heads. However, despite this great interest, its properties are not fully understood. For an in depth analysis of important physical properties as, e.g., electric transport or magnetic anisotropy, a detailed understanding of the distribution of magnetic moments on an atomic level is necessary. Using our first principles locally self-consistent multiple scattering method, we calculate the magnetic ground state structure for a large supercell model of Permalloy. Our code allows us to solve both the usual nonrelativistic Schrodinger equation as well as the fully relativistic Dirac equation and to find the magnitude and direction of the magnetic moments at each atomic site. While the nonrelativistic calculation yields a collinear ground state in accordance with previous calculations, we find the ground state for the fully relativistic calculation to be slightly noncollinear. We also investigate the influence of variations in the iron concentration on the distribution of magnetic moments. (c) 2007 American Institute of Physics.