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

The properties of Nb, Mo, and Cr as the spacers in magnetic/nonmagnetic multilayers are examined. Utilizing the simple Ruderman-Kittel-Kasuya-Yosida-like response-function theory, one can elucidate not only which features of the bulk band structures are relevant but also discuss the implications of the spacers being inhomogeneously strained. The crucial question proves to be determining which caliper can resist all the broadening effects to appear actually as a macroscopic quantum effect. One mechanism is to minimize scattering by selecting wave functions with substantial s and p character. Another is to maximize the effective velocity and thereby minimize dephasing by the existing scattering. In Nb (110) and Mo (100), such considerations select Kohn-anomaly calipers which arise from the N-centered ellipses. Consideration of resilience 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 be internally consistent in that they occur from the rim of the DELTA centered lens surfaces and involve the strong MiXing Of t2g and e(g) d states. The analysis also suggests several factors which help to understand the systematics observed for spacers across the transition series.