Article

Modulation of single and double spin torque oscillators

AIP Conf. Proc 01/2011; 1347:318-321. DOI: 10.1063/1.3601845

ABSTRACT We discuss modulation of metallic spin torque oscillators (STOs) based on single and double nano-contacts. The modulation behavior of both types of devices is characterized by equally spaced multiple sidebands, which can be ascribed mostly to a frequency modulation phenomenon. However, quantitative examination reveals that amplitude modulation is also present in both types of devices. We also show the feasibility of modulating the synchronized state of a double nano-contact STO. The synchronized state can be treated as a single oscillator, which is a very promising feature for future applications of STO arrays.z

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Available from: Yevgen Pogoryelov, Jul 29, 2015
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    • "Recently, a more thorough analysis provided the first experimental evidence [12] of amplitude modulation. It also showed excellent quantitative agreement with a non-linear frequency and amplitude modulation (NFAM) theory [11] as well as modulation up to 3.2 GHz [13], [14], [52]. "
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    ABSTRACT: We present a comprehensive review of the most recent advances in nanocontact spin torque oscillators (NC-STOs). NC-STOs are highly tunable, with both applied magnetic field and dc, broadband microwave signal generators. As opposed to the nanopillar geometry, where the lateral cross section of the entire device has been confined to a typically ${<}{rm 100}~{rm nm}$ diameter, in NC-STOs, it is only the current injection site that has been laterally confined on top of an extended magnetic film stack. Three distinct material combinations will be discussed: 1) a Co/Cu/NiFe pseudospin valve (PSV) where both the Co and NiFe have a dominant in-plane anisotropy; 2) a Co/Cu/ $[{rm Co}/{rm Ni}]_{4}$ orthogonal PSV where the Co/Ni multilayer has a strong perpendicular anisotropy; and 3) a single NiFe layer with asymmetric non-magnetic Cu leads. We explore the rich and diverse magnetodynamic modes that can be generated in these three distinct sample geometries.
    IEEE Transactions on Magnetics 06/2014; 50(6):1-7. DOI:10.1109/TMAG.2014.2305762 · 1.21 Impact Factor
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    • "The modulation follows a recently developed theory [11]–[16], and the device can hence be utilized in applications without any specific changes to modulation schemes. "
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    ABSTRACT: We show that the frequency of a magnetic tunnel junction (MTJ)-based spin torque oscillator (STO) can be doubled and the first harmonic entirely suppressed by orienting the free and fixed layer magnetizations in an antiparallel (AP) state. The angular dependence of the harmonics allows us to extract the free layer precession angle, which follows a parabolic decrease from a maximum of 20{sup o} in the AP state to about 10{sup o} at 25{sup o} of misalignment. Frequency-doubling provides both a promising way for increasing the frequency of MTJ-STOs and a means for high-rate frequency shift keying using only a small magnetic field.
    Journal of Applied Physics 10/2011; 110(7). DOI:10.1063/1.3647759 · 2.19 Impact Factor
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