Analog and digital phase modulation of spin torque nano-oscillators

Abstract

Spin torque nano-oscillators (STNO) are nanoscale and multifunctional devices with wide band frequency tunability. Their RF properties are well suited to define novel schemes for wireless communication used within wireless sensor networks (WSN). To meet constraints of low power consumption and autonomy, WSNs use basic protocols for data transmission which are amplitude, frequency and phase shift keying (ASK, FSK, PSK). ASK and FSK have been demonstrated for STNOs but implementation of PSK has been left open so far.Phase shift keying requires a stable phase and a well-defined reference phase, while in free running STNOs the phase is free and characterized by large fluctuations. Here we introduce a special PSK technique for STNOs by combining their modulation and injection locking functionality. Injection locking provides a stable reference phase and reduces the STNO phase noise making the system compatible with IEEE standards. We used injection locking at 2f and f/2. The STNO intrinsic frequency is detuned via injecting additional modulation

Stress-induced modification of gyration dynamics in stacked double-vortex structures studied by micromagnetic simulations

“…Figure 3(a) shows the simulated dynamical spectra of the CoFe(10)/NM(d NM )/Py(20) trilayer (d = 300 nm) for different d NM for the (c 1 c 2 ; p 1 p 2 ) = (1; 1) case. Similar to the p 1 p 2 = −1 case, the dynamics of the double-vortex structure corresponds to the resonant gyration of the uncoupled isolated CoFe (10) and Py (20) vortices when the magnetostatic coupling is negligible, i.e. the NM spacer is thick (t NM ⩾ 200 nm).…”

“…For t NM ⩾ 200 nm, the resonances occur at f lo = f Py = 0.56 GHz and f hi = f CoFe = 0.62 GHz, corresponding to the resonances of the uncoupled CoFe (10) and Py(20) disks, respectively. Decreasing the spacer thickness leads to a redshift of the eigen-frequencies of both layers, as well as to a decreased frequency separation ∆f ≡ f hi − f lo , due to the increased magnetostatic coupling between the magnetic layers, which pulls the frequencies closer to each other.…”

“…The complex dynamics of coupled vortex modes was studied in detail in [5], revealing a fine splitting of the corresponding resonant frequencies. The recent demonstration of phase noise reduction in vortex-based spin-torque oscillators locked to an external rf current [6,7] provides the potential for system-level integration of vortex-based devices for such applications as spectrum analysis [8,9], microwave receivers/transmitters [10] and spintronics-based neuromorphic computing [11,12]. While all these features make vortex-based nano-oscillators interesting as nanoscale rf sources, the major drawback remains their low frequency tuneability when operated in the linear regime.…”

Robust phase shift keying modulation method for spin torque nano-oscillator

“…PSK modulation for STNOs remained unsolved until 2019. A. Litvinenko et al claims the first investigation on phase modulation for STNO [36]. The proposed phase modulation method is based on the phase locking phenomenon.…”

Non-hermiticity in spintronics: oscillation death in coupled spintronic nano-oscillators through emerging exceptional points

“…We believe that the presented results create an important connection between the non-hermitian physics of EPs and spintronics, an area of research that has crucial technological implications for data stor-age and processing [47,48] , sensor technology [47,49] , wide-102 band high-frequency communications [50][51][52][53][54][55] , and, more 103 recently, bio-inspired networks for neuromorphic com-104 puting beyond CMOS [56,57] . Up to now, coupled 105…”