Nonlinear spin-torque microwave resonance near the loss of spin state stability

• Published in: Solid state communications 2016-12, Vol.248, p.140-143
• Main Authors: Popkov, A.F., Kulagin, N.E., Demin, G.D.
• Format: Article
• Language: English
• Subjects: C. Magnetic tunnel junction; C. Spin-transfer torque; D. Microwave hysteresis; D. Microwave sensitivity; D. Spin diode effect
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2016.10.004

The paper analyzes microwave resonant response of the spin-torque diode. The considered spin-torque diode is a magnetic tunnel junction with a nano-pillar structure. The magnetization of the free layer has a tilt caused by an action of the inclined magnetic field in the plane of the structure. Taking into account the effect of spin torque transfer we define stability regions of stationary states of magnetization in the free layer as a function of the azimuth angle of the magnetic field and bias DC current. Microwave volt-watt sensitivity of the spin diode for the obtained stationary states is calculated. It is shown that non-linear frequency shift of the resonance line width limits maximum sensitivity of the spin diode near the critical bias current corresponding to the point of the transition to the self-oscillating mode. Besides that, overlapping of frequency branches occurs in the resonant response as the critical point approach, which is different from the foldover effect in the nonlinear ferromagnetic resonance induced by an alternating magnetic field. •Spin-state stability borders define the regions of maximum microwave sensitivity.•Nonlinear linewidth shift of the spin-torque resonance limits microwave sensitivity.•Self-intersection of resonant branches may be observed near critical bias current.