Exchange coupling and noncollinear magnetic states in Ni/Fe-n/Ni(100) multilayers

The Ni interlayer exchange coupling (IEC) and the atomic-scale magnetic configurations in fcc Ni/Fe-n/Ni(100) multilayers, with ultrathin Fe spacers, are investigated using first-principles density-functional theory including the noncollinear spin formalism. The trends with changing Fe thickness (n) between 3 and 5 monolayers (MLs) are examined. For n = 3 and 4 MLs, we find the ground state to display antiferromagnetic IEC between the Ni films, while for the 5-ML Fe spacer, the IEC changes into ferromagnetic. Upon reversal of the magnetization alignment, from antiparallel to parallel, between the Ni films with 3- and 4-ML thick Fe spacer, we find noncollinear magnetic configurations in the Fe layer as the lowest-energy states, which are related to the magnetic instability towards noncollinear solutions in bulk gamma-Fe. (C) 2014 Elsevier Ltd. All rights reserved.