MAGNETIC MULTILAYERS WITH (NB,MO,CR) SPACER MATERIALS

The properties of Nb, Mo, and Cr as the spacers in magnetic/nonmagneti c multilayers are examined. Utilizing the simple Ruderman-Kittel-Kasuy a-Yosida-like response-function theory, one can elucidate not only whi ch features of the bulk band structures are relevant but also discuss the implications of the spacers being inhomogeneously strained. The cr ucial question proves to be determining which caliper can resist all t he broadening effects to appear actually as a macroscopic quantum effe ct. One mechanism is to minimize scattering by selecting wave function s with substantial s and p character. Another is to maximize the effec tive velocity and thereby minimize dephasing by the existing scatterin g. In Nb (110) and Mo (100), such considerations select Kohn-anomaly c alipers which arise from the N-centered ellipses. Consideration of res ilience to scattering effects is crucial to explaining why the Mo (100 ) repeat distance appears at three layers instead of at the two layers as seen in Cr. The uniform long repeat distances seen in Cr for the ( 100), (211), and (110) and the (110) repeat distance in Mo appear to b e internally consistent in that they occur from the rim of the DELTA c entered lens surfaces and involve the strong MiXing Of t2g and e(g) d states. The analysis also suggests several factors which help to under stand the systematics observed for spacers across the transition serie s.