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Highly sensitive nanoscale spin-torque diode

Abstract

Highly sensitive microwave devices that are operational at room temperature are important for high-speed multiplex telecommunications. Quantum devices such as superconducting bolometers possess high performance but work only at low temperature. On the other hand, semiconductor devices, although enabling high-speed operation at room temperature, have poor signal-to-noise ratios. In this regard, the demonstration of a diode based on spin-torque-induced ferromagnetic resonance between nanomagnets represented a promising development, even though the rectification output was too small for applications (1.4 mV mW−1). Here we show that by applying d.c. bias currents to nanomagnets while precisely controlling their magnetization-potential profiles, a much greater radiofrequency detection sensitivity of 12,000 mV mW−1 is achievable at room temperature, exceeding that of semiconductor diode detectors (3,800 mV mW−1). Theoretical analysis reveals essential roles for nonlinear ferromagnetic resonance, which enhances the signal-to-noise ratio even at room temperature as the size of the magnets decreases.

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Figure 1: Nonlinear effect in nanomagnets and the spin-torque diode device.
Figure 2: Basic device characteristics.
Figure 3: d.c. bias and RF input power dependence.
Figure 4: Noise characteristics.

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Acknowledgements

We thank A. A. Tulapurkar and S. Yakata for discussions. This research was conducted with the financial support of the Grant-in-Aid for Scientific Research (S), No. 23226001 from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

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Contributions

S.M. and S.I. performed the experiments and the analysis; they wrote the paper with T.N., N.M. and Y.S.’s appraisals and inputs. H.T. and S.M. conducted the simulations. S.I., T.S., H.K., K.Y., A.F. and S.Y. prepared the samples. E.T. and K.A. helped with the development of the theory and the measurements, respectively. T.T. and H.I conducted the theoretical analysis about the spin motive force. Y.S. conceived and designed the experiment and developed the theory. All authors contributed to the general discussion.

Corresponding author

Correspondence to Y. Suzuki.

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Miwa, S., Ishibashi, S., Tomita, H. et al. Highly sensitive nanoscale spin-torque diode. Nature Mater 13, 50–56 (2014). https://doi.org/10.1038/nmat3778

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