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Phase-locking in double-point-contact spin-transfer devices

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Abstract

Spin-transfer1,2 in nanometre-scale magnetic devices results from the torque on a ferromagnet owing to its interaction with a spin-polarized current and the electrons' spin angular momentum. Experiments have detected either a reversal3,4,5,6,7,8,9,10,11,12,13,14,15,16 or high-frequency (GHz) steady-state precession17,18,19,20,21,22,23 of the magnetization in giant magnetoresistance spin valves and magnetic tunnel junctions with current densities of more than 107 A cm-2. Spin-transfer devices may enable high-density, low-power magnetic random access memory24,25 or direct-current-driven nanometre-sized microwave oscillators. Here we show that the magnetization oscillations induced by spin-transfer in two 80-nm-diameter giant-magnetoresistance point contacts in close proximity to each other can phase-lock into a single resonance over a frequency range from approximately <10 to >24 GHz for contact spacings of less than about ∼200 nm. The output power from these contact pairs with small spacing is approximately twice the total power from more widely spaced (∼400 nm and greater) contact pairs that undergo separate resonances, indicating that the closely spaced pairs are phase-locked with zero phase shift. Phase-locking may enable control of large arrays of coupled spin-transfer devices with increased power output for microwave oscillator applications.

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Figure 1: Overview of double-point-contact device.
Figure 2: High-frequency output for devices with two 80-nm point contacts and varied intercontact spacing.
Figure 3: Histograms showing statistical distribution of spin-transfer behaviour in devices with two 80-nm-diameter contacts and varied centre-to-centre contact spacing.
Figure 4: High-frequency output for two 80-nm point contacts with 150-nm intercontact spacing.

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Acknowledgements

We thank W. H. Rippard, T. J. Silva and S. E. Russek for discussions. This work was supported in part by the DARPA SPINS programme through Motorola.

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Authors and Affiliations

  1. Technology Solutions Organization, Freescale Semiconductor Inc., Arizona, 85224, Chandler, USA

    F. B. Mancoff, N. D. Rizzo, B. N. Engel & S. Tehrani

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  1. F. B. Mancoff
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  2. N. D. Rizzo
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  3. B. N. Engel
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  4. S. Tehrani
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Correspondence to F. B. Mancoff.

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Mancoff, F., Rizzo, N., Engel, B. et al. Phase-locking in double-point-contact spin-transfer devices. Nature 437, 393–395 (2005). https://doi.org/10.1038/nature04036

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