Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.40: Poster

Tuesday, March 27, 2007, 15:00–19:00, Poster A

Spin transfer torque in granular films AgCo and spin-valve structure Co/Cu/CoNiFeSiB — •Yuansu Luo¹, Markus Esseling¹, Markus Münzenberg², and Konrad Samwer¹ — ¹I. Phys. Institut — ²IV. Phys. Insitut, Universität Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen

We explore spin transfer torque (STT) effect in granular films Ag₇₀Co₃₀ and spin-valve structure Co/Cu/(CoNiFe)₇₄(SiB)₂₆ by means of point contact technique. Several special properties, such as single-domain properties of Co nanoparticles, a large GMR effect (55% measured at 4.2K) in AgCo, a small coercivity (H_c≈1 Oe) and a low magnetization (M_s≈0.7 kG) of the amorphous free layer (CoNiFe)₇₄(SiB)₂₆, are convenient for STT observations. A novel STT effect is observed in the granular film, as the current rises above a threshold value I_c. It is accompanied with an abrupt decrease in resistance (R), presumably due to further alignment of small size Co granules. The behavior is polar and I_c disproportional to the magnetic field. For the spin-valve structure a normal current-induced magnetization switching was measured under a standard condition, i.e. an electron flux from the fixed Co-layer to the amorphous free layer (CoNiFe)₇₄(SiB)₂₆ stabilizes the parallel alignment (low R), while an opposite current results in the antialignment of two magnetic layers (high R). Supported by DFG-project, SA 337/9-1