INTERFACE ROUGHNESS, MAGNETIC-MOMENTS, AND COUPLINGS IN (A)M/(CR)N(001) SUPERLATTICES (A=FE,CO,NI)

We use the real-space tight-binding method to determine the magnetic moments and the interlayer magnetic couplings (IMC) of (A)m/(Cr)n (A = Fe, Co, Ni) superlattices (SL) with perfect or diffuse A/Cr interfaces. For perfect SL, the IMC oscillate with a short period in agreement with experiment. For the same SL with an interface roughness coming from interfacial ordered compounds, the occurrence of interfacial frustrated Cr-Fe bonds and of Cr magnetic-moment instability can lead to a strong reduction of the Cr moments even if n is large (n congruent-to 30) and also to a damping and even the disappearance of the previous IMC oscillations. Therefore, the Cr spacer is not - as often assumed - a passive medium transmitting indirect RKKY-like interactions.