engleski

Domain wall displacement induced by spin-polarized current in spin valves

We present experiments showing back and forth domain wall displacement induced by a spin polarized current, without any applied external field, in agreement with Slonczewski and Berger predictions. We have studied domain wall motion in stripes of Co/Cu/CoFeB and Co/Cu/NiFe spin valves. Our samples were designed to allow easy magnetization control. Spin polarized current was injected along the stripe axis (CIP configuration). Electrical measurements were performed at room temperature using the spin valve effect to probe and observe the DW displacement in the magnetically soft CoFeB or NiFe. Low current densities were required to switch the CoFeB magnetization: 8.5 x10^5 A/cm^2 at almost zero fields (1 Oe). We have also obtained an interesting evidence of a new effect (domain wall oscillations) as a response to the current injection. This effect is now investigated and it requires complementary RF measurements. In addition we show a strong dependence of the critical current with the applied field, which can be alternatively described as a strong decrease of the coercive fields when the current is increased. This feature is important for application to future MRAMs based on spin transfer domain wall motion.

spintronics; spin transfer; domain wall displacement

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