  We present an all-Heusler architecture which could be used as a rational
design scheme for achieving high spin-filtering efficiency in the
current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. A
Co2MnSi/Ni2NiSi/Co2MnSi trilayer stack is chosen as the prototype of such an
architecture, of which the electronic structure and magnetotransport properties
are systematically investigated by first principles approaches. Almost
perfectly matched energy bands and Fermi surfaces between the all-Heusler
electrode-spacer pair are found, indicating large interfacial spin-asymmetry,
high spin-injection efficiency, and consequently high GMR ratio. Transport
calculations further confirms the superiority of the all-Heusler architecture
over the conventional Heusler/transition-metal(TM) structure by comparing their
transmission coefficients and interfacial resistances of parallel conduction
electrons, as well as the macroscopic current-voltage (I-V) characteristics. We
suggest future theoretical and experimental efforts in developing novel
all-Heusler GMR junctions for the read heads of the next generation
high-density hard disk drives (HDDs).
