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Current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) characteristics were investigated in a Co 2 MnSi (CMS)/Ag/CMS fully epitaxial device and compared to those in a CMS/Cr/CMS device systematically. Reflection high-energy electron diffraction and transmission electron microscopy images showed the two samples had no remarkable differences and little interdiffusion. The large spinasymmetry of electron scattering was found at the CMS/Ag inteface compared with that at the CMS/Cr interface. Finally, the largest magneto-resistance (MR) ratio of 28.8% was observed at room temperature in the CMS/Ag/CMS CPP-GMR device.

Fully epitaxial Co 2 Fe x Mn 1Àx Si(CFMS)/Ag/Co 2 Fe x Mn 1Àx Si current-perpendicular-to-plane giant magnetoresistive devices with various Fe/Mn ratios x and top CFMS layer thicknesses t CFMS were prepared. The highest magnetoresistance (MR) ratios, 58% at room temperature and 184% at 30 K, were observed in the sample with x ¼ 0.4 and t CFMS ¼ 3 nm. Enhancement of interface spinasymmetry was suggested for x ¼ 0.4 compared with that at x ¼ 0. A MR ratio of 58% was also observed even in a very thin trilayer structure, CFMS(4 nm)/Ag(3 nm)/CFMS(2 nm), which is promising for a next-generation magnetic read sensor for high-density hard disk drives. V

We study spin torque oscillators comprised of a perpendicular spin injection layer (SIL) and a planar field generating layer to reveal the influence of the spin polarization of SIL material on the critical current density, JC, to induce microwave oscillation. Two systems with different SIL are compared: one with a highly spin-polarized Heusler alloy, Co2Fe(Ga0.5Ge0.5) (CFGG), and the other a prototypical Fe2Co alloy. Cross sectional scanning transmission electron microscopy observations show the B2-ordered structure in a 3-nm-thick CFGG SIL, a prerequisite for obtaining half-metallic transport properties. Current induced microwave oscillations are found at frequencies of ∼15 GHz for both systems. However, the current needed to cause the oscillations is ∼50% smaller for films with the CFGG SIL compared to those of the Fe2Co SIL. These results are in accordance with micromagnetic simulations that include spin accumulation at the SIL.