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Mario Carpentieri
Ruolo
Professore Associato
Organizzazione
Politecnico di Bari
Dipartimento
Dipartimento di Ingegneria Elettrica e dell'Informazione
Area Scientifica
Area 09 - Ingegneria industriale e dell'informazione
Settore Scientifico Disciplinare
ING-IND/31 - Elettrotecnica
Settore ERC 1° livello
PE - Physical sciences and engineering
Settore ERC 2° livello
PE7 Systems and Communication Engineering: Electrical, electronic, communication, optical and systems engineering
Settore ERC 3° livello
PE7_4 - (Micro and nano) systems engineering
We report measurements of spin-torque-driven oscillations in magnetic multilayer devices containing two in-plane-oriented free layers designed to have significant coupling between them. They are driven to oscillate by spin-transfertorquefromtwoperpendicularlyorientedpolarizers.Forbothmeasureddevicesandmicromagnetic simulations,wefindthattheoscillationsinthetwofreelayersarephaselocked,resultinginafrequencydoubling and large output signals. The simulations suggest that the oscillations are due to spatially nonuniform dynamics characterized by coupled large-amplitude motion of the two free layers.
The magnetization switching of a thin ferromagnetic layer placed on top of a heavy metal (such as Pt, Ta, or W) driven by an in-plane current has been observed in recent experiments. The magnetization dynamics of these processes is studied in a full micromagnetic framework which takes into account the transfer-torque from spin Hall effect due to the spin-orbit coupling. Simulations indicate that the reversal occurs via nucleation of complex magnetization patterns. In particular, magnetic bubbles appear during the reversal of the magnetization in the perpendicular configuration while for the in-plane configuration, nucleation of vortexes is observed.
The Magnetic Equivalent Circuits (MECs) technique is a powerful tool for machine analysis and power losses computation. Here, use is made of the Diagonal Mesh Equivalent (DME) to solve the equivalent electrical circuit for the branch fluxes to be easily computed and related to the machine compartments of technical interest. These are represented by the air gap, stator and rotor to name a few. Hysteresis loops have been computed, along with the static power losses, for assigned stator thicknesses and compared to ones alternatively obtained by the Modified Scalar Preisach Model. This study is especially aimed at giving improved issues to those who are engaged in the design of magnetic components for electrical machines.
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