Article

Current-induced resonance and mass determination of a single magnetic domain wall

Department of Physics, Keio University, Yokohama, 223-8522, Japan.
Nature (Impact Factor: 42.35). 11/2004; 432(7014):203-6. DOI: 10.1038/nature03009
Source: PubMed

ABSTRACT A magnetic domain wall (DW) is a spatially localized change of magnetization configuration in a magnet. This topological object has been predicted to behave at low energy as a composite particle with finite mass. This particle will couple directly with electric currents as well as magnetic fields, and its manipulation using electric currents is of particular interest with regard to the development of high-density magnetic memories. The DW mass sets the ultimate operation speed of these devices, but has yet to be determined experimentally. Here we report the direct observation of the dynamics of a single DW in a ferromagnetic nanowire, which demonstrates that such a topological particle has a very small but finite mass of 6.6 x 10(-23) kg. This measurement was realized by preparing a tunable DW potential in the nanowire, and detecting the resonance motion of the DW induced by an oscillating current. The resonance also allows low-current operation, which is crucial in device applications; a DW displacement of 10 microm was induced by a current density of 10(10) A m(-2).

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    • "The half-ring shape was designed for two reasons. First, it facilitates the DW creation [28]. As can be seen from the micromagnetic simulations presented on Fig.1 "
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    ABSTRACT: Shifting electrically a magnetic domain wall (DW) by the spin transfer mechanism is one of the future ways foreseen for the switching of spintronic memories or registers. The classical geometries where the current is injected in the plane of the magnetic layers suffer from a poor efficiency of the intrinsic torques acting on the DWs. A way to circumvent this problem is to use vertical current injection. In that case, theoretical calculations attribute the microscopic origin of DW displacements to the out-of-plane (field-like) spin transfer torque. Here we report experiments in which we controllably displace a DW in the planar electrode of a magnetic tunnel junction by vertical current injection. Our measurements confirm the major role of the out-of-plane spin torque for DW motion, and allow to quantify this term precisely. The involved current densities are about 100 times smaller than the one commonly observed with in-plane currents. Step by step resistance switching of the magnetic tunnel junction opens a new way for the realization of spintronic memristive devices.
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    • "The results show that domain-wall motion follows external magnetic field up to ~ 100 MHz while magnetization rotation does so all the way up to GHz. Theses results showed that RF field driven domain-wall motion is slow [22], which corroborates the current driven domain motion observation in [18]. On the other hand, the results in [23] [24] suggest that domain-wall motion is fast despite the lack of domain analysis and control. "
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