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Sujet de stage / Master 2 Internship

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Magnetization dynamics in magnetic nanostructures

Contact: DE-LOUBENS Gregoire, , gregoire.deloubens@cea.fr, +33 1 69 08 71 60
Summary:
The aim of this experimental internship is to study the linear and nonlinear regimes of magnetization dynamics in individual nanostructures. This will take place in the framework of an ANR project whose goal is to demonstrate the manipulation of high amplitude coherent spin waves in devices combining concepts of magnonics and spintronics. A funded PhD thesis will follow.
Possibility of continuation in PhD: Oui
Deadline for application:25/03/2019

Full description:
One current goal of spintronics is the development of a sustainable information technology based on the transport of pure spin currents. For this, a promising approach is to combine spintronics and magnonics to excite, control and detect spin waves, or their quanta magnons, with characteristic frequencies and wavelengths from GHz to THz and from µm to nm, respectively. In this context, YIG, an insulating yttrium iron garnet, is a material of choice because of its particularly long spin-wave relaxation time. Moreover, the latter can be controlled by an electrical current injected in an adjacent layer of platinum thanks to spin transfer torque [2,3], This torque of spin-orbit origin also allows the generation of auto-oscillations of the magnetization [4]. It is now timely to understand and control the nonlinear properties of these hybrid devices. These nonlinear properties, directly inherited for the equation of motion of magnetization, are crucial since they govern the type of dynamics generated by spin-orbit torque [5,6]. To control the excitation spectrum and the nonlinear properties, it is possible to nanopattern the magnetic film [7] and to engineer the properties of the material itself, in particular its perpendicular magnetic anisotropy [8]. The aim of this internship will thus be to measure the spin wave spectrum and the nonlinear properties of Bismuth doped YIG nanostructures. For this, a unique home made equipment, a magnetic resonance force microscope (MRFM), will be used. This very sensitive near field microscopy technique uses a magnetic probe attached at the end of a very soft mechanical cantilever to detect magnetization dynamics in individual nanostructures [9].

[1] A. Chumak, et al., Magnon spintronics, Nature Phys. 11, 453-461 (2015)
[2] A. Hamadeh, et al., Full Control of the Spin-Wave Damping in a Magnetic Insulator Using Spin-Orbit Torque, Phys. Rev. Lett. 113, 197203 (2014)
[3] M. Evelt, et al., High-efficiency control of spin-wave propagation in ultra-thin yttrium iron garnet by the spin-orbit torque, Appl. Phys. Lett. 108, 172406 (2016)
[4] M. Collet, et al., Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque, Nature Commun. 7, 10377 (2016)
[5] V. Demidov, et al., Direct observation of dynamic modes excited in a magnetic insulator by pure spin current, Sci. Rep. 6, 32781 (2016)
[6] M. Evelt, et al., Emission of coherent propagating magnons by insulator-based spin-orbit torque oscillator, arXiv:1807.09976
[7] C. Hahn, et al., Measurement of the intrinsic damping constant in individual nanodisks of Y3Fe5O12 and Y3Fe5O12|Pt, Appl. Phys. Lett. 104, 152410 (2014)
[8] L. Soumah, et al., Ultra-low damping insulating magnetic thin films get perpendicular, Nature Commun. 9, 3355 (2018)
[9] O. Klein, et al., Ferromagnetic resonance force spectroscopy of individual submicron-size samples, Phys. Rev. B 78, 144410 (2008)
Technics/methods used during the internship:
magnetic force microscopy; high frequency techniques

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