Magnetism and atomic short range order in iron-rich B.C.C. alloys

Full text: Magnetism and the ordered structures that iron alloys form are closely interrelated via their underlying electronic structure. Since the Curie temperatures of iron-rich b.c.c. alloys are often comparable with their compositional ordering or phase segregation transition temperatures, the magnetic state can play a crucial role in determining the type of alloy formed and its dependence on its thermal history. Long-range magnetic order spin-polarizes the electronic structure producing different electronic mechanisms for arranging the atoms from those set by the paramagnetic alloy in which the effects of spin-fluctuations are important. We illustrate this close relationship between magnetism and atomic short range order in iron-rich b.c.c. alloys by presenting details of the application of our 'first-principles' theory of compositional and magnetic correlations to Fe75AI25, Fe80AI20, and Fe87V13 ferromagnetic alloys. For the first time, the magnetic and compositional correlations have been treated on equal basis within a theoretical framework. We further suggest that measurement of atomic short range order in metallic alloys be used to test models of spin fluctuations in the paramagnetic state of metallic magnets. In such systems, the longstanding controversy of whether there is massive or modest amount of magnetic short-range order could be resolved