Spin engineering with Fe–Au monolayers

Abstract FeAu superlattices were grown using MBE by alternative deposition of Fe(0 0 1) and Au(0 0 1) atomic layers. Polar MOKE loops taken at the room temperature showed that all superlattices with single Fe monolayers (MLs) were magnetized along the film normal but the character of the hysteresis loop depended strongly on the repetition number N in a (Fe 1 Au 1 ) N stack, where Fe 1 Au 1 denotes a single sequence of the Fe(0 0 1) and Au(0 0 1) MLs. The loop character changed from a low remanence one for N =20 to a narrow ( H C =50 Oe) rectangular one for N =3. (Fe 1 Au 1 ) 3 stacks, denoted as (FeAu) 3 , were used to construct multilayers, in which they were spaced by K Au(0 0 1) atomic layers (AL). In the tri-layer , (Fe 1 Au 1 ) 3 /Au( d Au )/(Fe 1 Au 1 ) 3 , antiferromagnetic exchange coupling was clearly observed around the Au(0 0 1) spacer thickness d Au =10 AL (about 2 nm). For [(Fe 1 Au 1 ) 3 /Au ( d Au )]× M ( M =4,6) the magnetization process becomes more complicated revealing a sharp multistage spin-flip transition including well-distinguished surface spin flip.