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.
At a glance
- Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475 (1988). et al.
- Giant magnetic tunneling effect in Fe/Al2O3/Fe junction. J. Magn. Magn. Mater. 139, L231–L234 (1995). &
- Large magnetoresistance at room temperature in ferromagnetic thin film tunnel junctions. Phys. Rev. Lett. 74, 3273–3276 (1995). , , &
- High tunnel magnetoresistance at room temperature in fully epitaxial Fe/MgO/Fe tunnel junctions due to coherent spin-polarized tunneling. Jpn. J. Appl. Phys. 43, L588–L590 (2004). , , , &
- Giant tunneling magnetoresistance at room temperature with MgO (100) tunnel barriers. Nature Mater. 3, 862–867 (2004). et al.
- Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions. Nature Mater. 3, 868–871 (2004). , , , &
- 230% room-temperature magnetoresistance in CoFeB/MgO/CoFeB magnetic tunnel junctions. Appl. Phys. Lett. 86, 092502 (2005). et al.
- Current-driven excitation of magnetic multilayers. J. Magn. Magn. Mater. 159, L1–L7 (1996).
- Emission of spin waves by a magnetic multilayer traversed by a current. Phys. Rev. B 54, 9353–9358 (1996).
- Current-induced switching of domains in magnetic multilayer devices. Science 285, 867–870 (1999). , , , &
- Observation of spin-transfer switching in deep submicron-sized and low resistance magnetic tunnel junctions. Appl. Phys. Lett. 84, 3118–3120 (2004). , , , &
- Evaluation of spin-transfer switching in CoFeB/MgO/CoFeB magnetic tunnel junctions. Jpn. J. Appl. Phys. 44, L1237–L1240 (2005). et al.
- Spin transfer switching and spin polarization in magnetic tunnel junctions with MgO and AlOx barriers. Appl. Phys. Lett. 87, 232502 (2005). et al.
- Excitation of a magnetic multilayer by an electric current. Phys. Rev. Lett. 80, 4281–4284 (1998). et al.
- Microwave oscillations of a nanomagnet driven by a spin-polarized current. Nature 425, 380–382 (2003). et al.
- Bias-driven high-power microwave emission from MgO-based tunnel magnetoresistance devices. Nature Phys. 4, 803–809 (2008). et al.
- Spin-polarized transport in inhomogeneous magnetic semiconductors: Theory of magnetic/nonmagnetic p–n junctions. Phys. Rev. Lett. 88, 066603 (2002). , &
- Investigation of spin voltaic effect in a p–n heterojunction. J. Appl. Phys. 45, L663–L665 (2006). , &
- Magnetoamplification in a bipolar magnetic junction transistor. Phys. Rev. Lett. 105, 117202 (2010). , &
- Spin-torque diode effect in magnetic tunnel junctions. Nature 438, 339–342 (2005). et al.
- Spin-transfer-driven ferromagnetic resonance of individual nanomagnets. Phys. Rev. Lett. 96, 227601 (2006). et al.
- Measurement of the spin-transfer-torque vector in magnetic tunnel junctions. Nature Phys. 4, 67–71 (2008). , , , , &
- Quantitative measurement of voltage dependence of spin-transfer torque in MgO-based magnetic tunnel junctions. Nature Phys. 4, 37–41 (2008). et al.
- Bias and angular dependence of spin-torque in magnetic tunnel junctions. Phys. Rev. B 79, 224416 (2009). et al.
- Time-resolved measurement of spin-transfer-driven ferromagnetic resonance and spin torque in magnetic tunnel junctions. Nature Phys. 7, 496–501 (2011). , , , &
- Sensitivity of spin-torque diodes for frequency-tunable resonant microwave detection. J. Appl. Phys. 106, 053905 (2009). et al.
- Large diode sensitivity of CoFeB/MgO/CoFeB magnetic tunnel junctions. Appl. Phys. Express 3, 073001 (2010). et al.
- High spin-torque diode sensitivity in CoFeB/MgO/CoFeB magnetic tunnel junctions under DC bias currents. IEEE Trans. Magn. 47, 3373–3376 (2011). et al.
- Nonadiabatic stochastic resonance of a nanomagnet excited by spin torque. Phys. Rev. Lett. 105, 047202 (2010). , , &
- Voltage-induced ferromagnetic resonance in magnetic tunnel junctions. Phys. Rev. Lett. 108, 197203 (2012). et al.
- Enhancement of perpendicular magnetic anisotropy in FeB free layers using a thin MgO cap layer. J. Appl. Phys. 111, 07C723 (2012). et al.
- Nonlinear thermal effect on sub-gigahertz ferromagnetic resonance in magnetic tunnel junction. Appl. Phys. Lett. 103, 042404. et al.
- Spin-torque influence on the high-frequency magnetization fluctuations in magnetic tunnel junctions. Phys. Rev. Lett. 98, 077203 (2007). et al.
- Line shape distortion in a nonlinear auto-oscillator near generation threshold: application to spin-torque nano-oscillators. Phys. Rev. Lett. 100, 167201 (2008). , , , &
- Excitations of incoherent spin-waves due to spin-transfer torque. Nature Mater. 3, 877–881 (2004). , , , &
- Electric-field-induced ferromagnetic resonance excitation in an ultrathin ferromagnetic metal layer. Nature Phys. 8, 491 (2012). et al.
- Generalization of the Landau-Lifshitz-Gilbert equation for conducting ferromagnets. Phys. Rev. Lett. 102, 086601 (2009). &
- Temperature and field dependence of high-frequency magnetic noise in spin valve devices. Appl. Phys. Lett. 82, 91–93 (2003). , &
- Noise properties of a resonance-type spin-torque microwave detector. Appl. Phys. Lett. 99, 032507 (2011). et al.
- Tunnel magnetoresistance above 170% and resistance-area product of 1 Ω(μm)2 attained by in situ annealing of ultra-thin MgO tunnel barrier. Appl. Phys. Exp. 4, 033002 (2011). et al.
- et al. 12th Joint MMM/Intermag Conf. BU-09 (IEEE Magnetic Society and The American Institute of Physics).
- Thermal fluctuations of a single-domain particle. Phys. Rev. 130, 1677–1686 (1963).
- Supplementary Information (1,857 KB)