Single spin-torque vortex oscillator using combined bottom-up approach and e-beam lithography

A combined bottom-up assembly of electrodeposited nanowires and electron beam lithography technique has been developed to investigate the spin transfer torque and microwave emission on specially designed nanowires containing a single Co/Cu/Co pseudo spin valve. Microwave signals have been obtained even at zero magnetic field. Interestingly, high frequency vs. magnetic field tunability was demonstrated, in the range 0.4 - 2 MHz/Oe, depending on the orientation of the applied magnetic field relative to the magnetic layers of the pseudo spin valve. The frequency values and the emitted signal frequency as a function of the external magnetic field are in good quantitative agreement with the analytical vortex model as well as with micromagnetic simulations.Comment: 9 pages, 4 figure

Phase locking dynamics of dipolarly coupled vortex-based spin transfer oscillators

Phase locking dynamics of dipolarly coupled vortices excited by spin-polarized current in two identical nanopillars is studied as a function of the interpillar distance L. Numerical study and analytical model have proved the remarkable efficiency of magneto-static interaction to achieve phase locking. Investigating the dynamics in the transient regime towards phase locking, we extract the evolution of the locking time \tau, the coupling strength {\mu} and the interaction energy W. Finally, we compare this coupling energy with the one obtained by simple model.Comment: 4 pages, 4 figure

Optimizing magneto-dipolar interactions for synchronizing vortex based spin-torque nano-oscillators

We report on a theoretical study about the magneto-dipolar coupling and synchronization between two vortex-based spin-torque nano-oscillators. In this work we study the dependence of the coupling efficiency on the relative magnetization parameters of the vortices in the system. For that purpose, we combine micromagnetic simulations, Thiele equation approach, and analytical macro-dipole approximation model to identify the optimized configuration for achieving phase-locking between neighboring oscillators. Notably, we compare vortices configurations with parallel (P) polarities and with opposite (AP) polarities. We demonstrate that the AP core configuration exhibits a coupling strength about three times larger than in the P core configuration.Comment: 8 pages, 11 figure

Magnetic Behavior of Co/Pt and TbCo Nanocaps Assembly for Bit Pattern Media

Large area patterning of self-assembled alumina nanobumps, with hexagonally close-packed order, has been used to create ordered array of bit pattern magnetic media. We have studied the magnetic properties of perpendicular magnetic TbCo alloy and Co/Pt multilayers deposited on self assembled alumina nanobumps. Measurement of reversal field as a function of field intensity, as well as magnetic force microscopy images confirm the weakness of exchange coupling between bits in the case of Co/Pt multilayer while stronger coupling is observed in the case of TbCo alloys. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3535

Magnetic Behavior of Co/Pt and TbCo Nanocaps Assembly for Bit Pattern Media

Large area patterning of self-assembled alumina nanobumps, with hexagonally close-packed order, has been used to create ordered array of bit pattern magnetic media. We have studied the magnetic properties of perpendicular magnetic TbCo alloy and Co/Pt multilayers deposited on self assembled alumina nanobumps. Measurement of reversal field as a function of field intensity, as well as magnetic force microscopy images confirm the weakness of exchange coupling between bits in the case of Co/Pt multilayer while stronger coupling is observed in the case of TbCo alloys. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3535

Caracterização do pó da casca de coco verde usado como substrato agrícola.

O aumento do consumo de agua-de-coco verde e a vocacao natural para sua industrializacao vem causando problema de disposicao final do residuo gerado, ou seja, as cascas do fruto. A analise do comportamento historico da oferta de coco verde no mercado demonstra crescimento significativo.bitstream/CNPAT-2010/5862/1/Ct-054.pd

Microwave neural processing and broadcasting with spintronic nano-oscillators

Can we build small neuromorphic chips capable of training deep networks with billions of parameters? This challenge requires hardware neurons and synapses with nanometric dimensions, which can be individually tuned, and densely connected. While nanosynaptic devices have been pursued actively in recent years, much less has been done on nanoscale artificial neurons. In this paper, we show that spintronic nano-oscillators are promising to implement analog hardware neurons that can be densely interconnected through electromagnetic signals. We show how spintronic oscillators maps the requirements of artificial neurons. We then show experimentally how an ensemble of four coupled oscillators can learn to classify all twelve American vowels, realizing the most complicated tasks performed by nanoscale neurons