INSP

INSP

Nanostructures: growth, quantum effects and magnetism – Spins and magnetism, magneto-acoustics


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Team

  • Permanent members: Catherine Gourdon, Laura Thevenard

 

In ferromagnetic metallic or semiconductor materials, we have developed different approaches to manipulate magnetization in a non-inductive way, exploiting in particular the coupling with acoustic waves. Their wave nature and low attenuation open interesting perspectives for magnonics.

We are mainly interested in diluted magnetic semiconductors (C2N epitaxy by A. Lemaître), key materials in spin electronics as they could address both the “logic” and “memory” aspects of a device.

3 recent results:

  1. Magneto-elastic control of magnetization
  2. Magnetization control by femtosecond laser pulses
  3. Dynamics of domain walls

 

1. Magneto-elastic control of magnetization

In collaboration with Jean-Yves Duquesne from the Acoustics for Nanosciences team, we electrically excite surface acoustic waves (SAW) by interdigitated combs, in order to control the magnetization dynamics. Their wave nature and low attenuation open interesting perspectives for magnonics, see for example our contribution to the “2019 Surface Acoustic Wave Roadmap” [JPhysD19].

The experimental demonstration that a surface acoustic wave (SAW) traveling over a thin layer of (Ga,Mn)As or (Ga,Mn)(As,P) is resonantly absorbed when its frequency is equal to that of the magnetization precession (SAW FMR, [PRB14],[JPhysConMat18]), and the time-domain detection of the resulting magnetization precession [PRApp18] . Well-chosen conditions highlight magnetic nonlinearities:

in this resonant configuration, the experimental demonstration of the precessional inversion of this layer [PRB16prec] and [JPhysConMat18], for which we predicted the optimal conditions [PRB13], as well as the reversal in zero field under acoustic [PRevApp19] :

the demonstration of a halving of the coercivity of an out-of-plane magnetized layer by an acoustic wave, interpreted as a transient decrease of the domain wall nucleation energy [PRB16nuc] :

experimental estimation of the surface acoustic wave amplitude – collab. B. Croset (INSP) and L. Largeau (C2N)

The amplitude of the acoustic wave is a crucial parameter for the magnetization reversal. We have used two complementary approaches to estimate it, with a perfect agreement between the two [JAP17],[JAC16] :

2. Magnetization control by femtosecond laser pulses

The aim is to manipulate the magnetization over shorter times and by more local methods than with a magnetic field. For this we will use a femtosecond Kerr effect time-resolved “pump-probe” experiment, which allows to follow the magnetization dynamics over a few ns. The pump pulse has the effect of precessioning the magnetization.

Excitation of stationary spin waves

In the case where several spin waves are excited, we can extract from the difference between the frequencies the exchange constant of the material [APL15].

Caption: Typical experimental dynamic signal obtained by time-resolved Kerr effect in GaMnAsP (T=12 K).

 

Detection of standing spin waves: magneto-optical illusion

The fundamental mode has a uniform amplitude in the layer. The amplitude of the first excited mode is sinusoidal. Its integral is zero, and should therefore not give any magneto-optical signal. We have shown that it is the optical phase shift of the light penetrating the layer that allows its observation. A consequence is the surprising observation that the 2 modes seem to “rotate” in opposite directions [PRB17-sw].

Caption: (a) Different modes likely to be excited. (b) Dynamic reconstruction of the trajectory of the 2 observed modes. A magneto-optical illusion is at the origin of the different direction of gyration.

Quantitative estimation of the stationary temperature increase induced by the pump

The study of hysteresis cycles by magnetic linear dichroism as a function of the temperature and power of the pump has also allowed a quantitative estimation of the stationary temperature rise induced by the pump, and of its spatial gradient [JAP16].

Caption: (a) Radial profile of the temperature rise induced by a 17.5 µJ/cm² fluence pump: experiment (symbols) and modeling taking into account a contact thermal resistance (blue solid line). (b) Analytical calculation of the radial thermal profile and in the thickness of the layer. [JAP16]

 

3. Dynamics of domain walls

Undercurrent propagation: spin-transfer and spin-orbit effects

The wall propagation under current has been enriched in the last years by couples induced by spin-orbit effects, coming from a Rashba interfacial contribution, from the Dzyaloshinkii-Moriya interaction or from the spin Hall effect. In GaMnAs, the spin-orbit effects have a volume (Dresselhaus) and surface (Rashba) origin. We tested these models in a little-studied geometry: uniaxially magnetized GaMnAs tracks in the plane, and structured either parallel (C// configuration) or perpendicular (C┴ configuration) to the easy axis (Fig. 1a).

Caption: (a) Two track configurations studied, with the effective spin-orbit field shown as a recessed arrow. (b) Wall velocity under field + current (2µm track, C//) or current alone (10 µm track, C┴ ). (c) 2µm C// track observed by longitudinal Kerr microscopy, three successive current pulses.(B=11 G, T=40K, J=24.5 GA/m²) [PRB17-dwp]

 

Two important results have been robustly demonstrated:

  • in C// tracks, the walls move in the direction of the hole current, contrary to what is expected by the spin transfer.
  • In C┴ tracks, this propagation direction competes with that imposed by the spin-orbit effective field parallel to the magnetization in the domains, which acts as an external field.
  • In both types of tracks, the mobilities under current are very high, up to ten times larger than those observed in out-of-plane magnetized GaMnAs.

The usual spin transfer couple and the Rashba and Dresselhaus spin-orbit fields cannot satisfactorily explain our experimental observations. We therefore suggest that it may be an exacerbation of the spin transfer effect by the native spin-orbit coupling of GaAs, as predicted by Nguyen et al. and Garate et al..

 

Propagation under field

very fast propagation velocity (500 m/s) in GaMnAs layers magnetized in the plane [PRB12]

Caption: Propagation of domain walls under field (in-situ microcoil) in a 50nm in-plane magnetized GaMnAs layer. Longitudinal Kerr effect microscopy [PRB12]

 

  • Development of a semi-analytical model to explain wall velocity anomalies as a result of the excitation of wall bending modes [PRB13], [PRB11]

collaboration between the University of Latvia and the Solid State Physics Laboratory (Orsay)

  • Wall propagation in the hydrodynamic regime in GaMnAs layers magnetized perpendicular to the plane[PRB08]

 

Study of static domains to determine the micromagnetic parameters

  • demonstration of a slight increase in the exchange constant of GaMnAsP following the introduction of Phosphorus [PRB10_]
  • Determination of the exchange constant and the domain wall width in GaMnAs using Kerr microscopy [PRB07]

 

Main experimental techniques

 

Collaborations

  • Groups of M. Maaref at the Institut Préparatoire aux Études Scientifiques et Technologiques in La Marsa, and of K. Boujdaria at the Faculty of Sciences of Bizerte (Tunisia): magnetic characterization of GaMnAs(P) layers [JMMM13], [JMMM15] and calculation of magnetic parameters in kp method [PRB13], [JAP12]
  • L. Steren and M. Tortarolo, in the framework of LIFAN (International Franco-Argentine Laboratory in Nanosciences): domain wall propagation in MnAs s [APL12]
  • A. Cebers, University of Latvia: theoretical studies around domain wall resonance phenomena [PRB13]

 

Funding

  • PHC Utique

 

Publications

  • [PRB20] Time- and space-resolved nonlinear magnetoacoustic dynamics, M. Kraimia, P. Kuszewski, J.-Y. Duquesne, A. Lemaître, F. Margaillan, C. Gourdon, and L. Thevenard Phys. Rev. B 101, 144425 (2020)
  • [JAP20] Exploring the shear strain contribution to the uniaxial magnetic anisotropy of (Ga,Mn)As, M. Kraimia, L. Largeau, K. Boujdaria, B. Croset, C. Mocuta, A. Lemaître, C. Gourdon, and L. ThevenardJournal of Applied Physics 127, 093901 (2020)
  • [JPhysD19] The 2019 surface acoustic waves roadmap, P. Delsing, C. Gourdon, L. Thevenard et al. J. Phys. D : Applied Physics 52, 353001 (2019)
  • [PRevApp19] Field-Free Magnetization Switching by an Acoustic Wave, I. S. Camara, J.-Y. Duquesne, A. Lemaître, C. Gourdon, L. Thevenard, Phys. Rev. Applied 11, 014045 (2019)
  • [PRApp18] Optical Probing of Rayleigh Wave Driven Magnetoacoustic Resonance, P. Kuszewski, J.-Y. Duquesne, L. Becerra, A. Lemaître, S. Vincent, S. Majrab, F. Margaillan, C. Gourdon, and L. Thevenard,Phys. Rev. Applied 10, 034036 (2018)
  • [JPhysConMat18] Resonant magneto-acoustic switching : influence of Rayleigh wave frequency and wavevector, P. Kuszewski, I. S. Camara, N. Biarrotte, L. Becerra, J. von Bardeleben, W Savero Torres, A. Lemaître, C. Gourdon, J.-Y Duquesne, Journal of Physics : Condensed Matter 30 244003 (2018)
  • [PRB17-sw] Counter-rotating standing spin-waves : a magneto-optical illusion , S. Shihab, L. Thevenard, A. Lemaître, Catherine Gourdon, Physical Review B 95 144411 (2017)
  • [PRB17-dwp] Spin transfer and spin-orbit torques in in-plane magnetized (Ga,Mn)As tracks, L. Thevenard, B. Boutigny, N. Güsken, L. Becerra, C. Ulysse, S. Shihab, A. Lemaître, J.-V. Kim, V. Jeudy, C. Gourdon, Physical Review B 95 054422 (2017)
  • [PRB17-soliton] Acoustic solitons : A robust tool to investigate the generation and the detection of ultrafast acoustic waves, E. Péronne, N. Chuecos, L. Thevenard, and Bernard Perrin, Physical Review B 95 064306 (2017)
  • [JAP17] Vector network analyzer measurement of the amplitude of an electrically excited surface acoustic wave and validation by x-ray diffraction, I. Camara, B. Croset, L. Largeau, P. Rovillain, L. Thevenard, J.-Y. Duquesne, Journal of Applied Physics 121 044503 (2017)
  • [JAC16] Laboratory X-ray characterization of a surface acoustic wave on GaAs : the critical role of instrumental convolution, L. Largeau, I. Camara, J.-Y. Duquesne, C. Gourdon, P. Rovillain, L. Thevenard, B. Croset, Journal of Applied Crystallography 49 2073 (2016)
  • [PRB16prec] Precessional magnetization switching induced by a surface acoustic wave, L. Thevenard, I. S. Camara,S. Majrab, M. Bernard, P. Rovillain, A. Lemaître, C. Gourdon, and J.-Y. Duquesne, Physical Review B 93 134430 (2016)
  • [JAP16] Stationary thermal gradient induced by ultrafast laser excitation in a ferromagnetic layer, S. Shihab, L. Thevenard, A. Lemaître, C. Gourdon, J.-Y. Duquesne J. Appl. Phys. 119 153904 (2016)
  • [PRB16nuc] Strong reduction of the coercivity by a surface acoustic wave in an out-of-plane magnetized epilayer, L. Thevenard, I. S. Camara, J.-Y. Prieur, P. Rovillain, A. Lemaître, C. Gourdon, and J.-Y. Duquesne, Physical Review B 93, 140405(2016)
  • [JMMM15] Optimizing magneto-optical effects in the ferromagnetic semiconductor GaMnAs, H. Riahi, L. Thevenard, M. Maaref, B. Gallas, A. Lemaître, C. Gourdon, Journal of Magnetism and Magnetic Materials 395, 340 (2015)
  • [APL15] Systematic study of the spin stiffness dependence on Phosphorus alloying in the ferromagnetic semiconductor (Ga,Mn)As , S. Shihab, H. Riahi, L. Thevenard, H. J. Von Bardeleben, A. Lemaître, C. Gourdon, Appl. Phys. Lett. 106 142408 (2015)
  • [PRB14] Surface-acoustic-wave-driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers, L. Thevenard, C. Gourdon, J.Y. Prieur, H. J. von Bardeleben, S. Vincent, L. Becerra, L. Largeau, J.Y. Duquesne, Physical Review B 90, 094401 (2014)
  • [PRB13] Irreversible magnetization switching using surface acoustic waves, L. Thevenard, J.-Y. Duquesne, E. Peronne, H. J. von Bardeleben, H. Jaffres, S. Ruttala, J-M. George, A. Lemaître, and C. Gourdon, Physical Review B 87, 144402 (2013)
  • [JMMM13] Annealing effect on the magnetization reversal and Curie temperature in a GaMnAs layer, H. Riahi, W. Ouerghui, L. Thevenard, C. Gourdon, M.A. Maaref, A. Lemaître, O. Mauguin, C. Testelin, J. Magn. Mag. Mat. 342, 149 (2013)
  • [PRB13] Domain-wall flexing instability and propagation in thin ferromagnetic films, C. Gourdon, L. Thevenard, and S. Haghgoo, A. Cebers, Phys. Rev. B 88, 014428 (2013)
  • [PRB13] The influence of phosphorus content on magnetic anisotropy in ferromagnetic (Ga, Mn)(As,P)/GaAs thin films , M Yahyaoui, K Boujdaria, M Cubukcu, C Testelin and C Gourdon, J. Phys. : Condens. Matter 25 346001 (2013)
  • [APL12] Fast domain wall dynamics in MnAs / GaAs films Fast domain wall dynamics in MnAs / GaAs films, M. Tortarolo, L. Thevenard, H. J. von Bardeleben, M. Cubukcu, M. Eddrief, V. Etgens, C. Gourdon, Applied Physics Letters 101, 072408 (2012)
  • [PRB12] High domain wall velocities in in-plane magnetized (Ga,Mn)(As,P) layers, Thevenard, L., Hussain, S. von Bardeleben, H. Bernard, M. Lemaître, A. Gourdon, C., Physical Review B 85 064419 (2012)
  • [JAP12] The influence of the epitaxial strain on the magnetic anisotropy in ferromagnetic (Ga,Mn)(As,P)/GaAs thin films , M Yahyaoui, K Boujdaria, M Cubukcu, C Testelin and C Gourdon, J. App. Phys. 111 346001 (2012)
  • [PRB11] Domain wall propagation in ferromagnetic semiconductors : Beyond the one-dimensional model, L. Thevenard, C. Gourdon, S. Haghgoo, J-P. Adam, J. von Berdeleben, A. Lemaître, W. Schoch, A. Thiaville, Physical Review B 83, 245211 (2011)
  • [PRB10] Effect of picosecond strain pulses on thin layers of the ferromagnetic semiconductor (Ga,Mn)(As,P), L. Thevenard, E. Peronne, C. Gourdon, C. Testelin, M. Cubukcu, E. Charron, S. Vincent, A. Lemaître, and B. Perrin, Phys. Rev. B 82, 104422 (2010)
  • [PRB10_] Exchange constant and domain wall width in (Ga,Mn)(As,P) films with self-organization of magnetic domains, S. Haghgoo, M. Cubukcu, H. J. von Bardeleben, L. Thevenard, A. Lemaître, and C. Gourdon, Phys. Rev. B 82, 041301 (2010)
  • [PRB09] Unusual domain-wall motion in ferromagnetic semiconductor films with tetragonal anisotropy, C. Gourdon, V. Jeudy, A. Cēbers, A. Dourlat, Kh. Khazen, and A. Lemaître, Phys. Rev. B 80, 161202(R) (2009).
  • [PRB08] Field-Driven Domain Wall Dynamics in GaMnAs Films with Perpendicular Anisotropy, A. Dourlat, V. Jeudy, A. Lemaître, and C. Gourdon, Phys. Rev. B 78, 161303(R) (2008).
  • [Lemaître08] Strain control of the magnetic anisotropy in (Ga,M n) (As,P) ferromagnetic semiconductor layers, A. Lemaître, A. Miard, L. Travers, O. Mauguin, L. Largeau, C. Gourdon, V. Jeudy, M. Tran, and J.-M. George, Appl. Phys. Lett. 93, 021123 (2008).
  • [PRB07] Determination of the micromagnetic parameters in GaMnAs using domain theory, C. Gourdon, A. Dourlat, V. Jeudy, K. Khazen, H. J. von Bardeleben, L. Thevenard, and A. Lemaître, Phys. Rev. B 76, 241301(R) (2007).
  • [Dourlat07] Domain structure and magnetic anisotropy fluctuations in (Ga,Mn)As : Effect of annealing, A. Dourlat, V. Jeudy, C. Testelin, F. Bernardot, K. Khazen, C. Gourdon, L. Thevenard, L. Largeau, O. Mauguin, and A. Lemaître, J. Appl. Phys. 102, 023913 (2007).
  • [Dourlat08] Experimental determination of domain wall width and spin stiffness constant in ferromagnetic (Ga,Mn)As with perpendicular easy axis A. Dourlat, C. Gourdon, V. Jeudy,, K. Khazen, H.J. von Bardeleben, L. Thevenard, A. Lemaitre, Physica E 40 (2008) 1848–1850
  • [Dourlat07] Domain wall dynamics in annealed GaMnAs epilayers A. Dourlat, V. Jeudy, L. Thevenard, A. Lemaître, and C. Gourdon, J. Supercond. Nov. Magn. 20, 453 (2007).
  • [Dourlat07] Expansion and collapse of domains with reverse magnetization in GaMnAs epilayers with perpendicular magnetic easy axis A. Dourlat, C. Gourdon, V. Jeudy, C. Testelin, K. Khazen, J.L. Cantin, H.J. von Bardeleben, L. Thevenard, A. Lemaitre, IEEE Trans. Magn. 43, 3022 (2007).