Institut des
NanoSciences de Paris

Phonons and magnons

  • Catherine Gourdon (DR1)
  • Laura Thevenard (CR1)


See also the « Spin & Magnetism » page of INSP

Former members
  • Meriem Kraimia (PhD 2016-2020 between Sorbonne Université and Université de Carthage)
  • Piotr Kuszewski (PhD 2015-2018 ED397)
  • Ibrahima Sock Camara (Post-doc 2015-2016)
  • Sylvain Shihab (PhD 2012-2015 ED397)
  • Sanaz Haghgoo (PhD 2008-2012)
  • Alexandre Dourlat (PhD 2005-2008)

Recent publications

Main experimental technics :

- Kerr effect microscopy (polar and longitudinal configurations)
- time-resolved Kerr effect (pump-probe)
- surface acoustic waves (in Collaboration with the Acoustics for Nanosciences team)

We have been focusing on the study of the dilute magnetic semiconductor (Ga,Mn)As (epitaxied at the C2N by A. Lemaître), a prototype material that is key to the endeavors of spintronics to combine logic and storage functionnalities in a single component.

Recent results :

1. Magneto-elastic control of magnetization

In collaboration with Jean-Yves Duquesne in the Acoustics for Nanosciences team, we excite electrically surface acoustic waves using interdigitated transducers to control magnetization dynamics. Their wave-like nature and their weak attenuation pave the way for interesting applications in magnonics. Latest results include :

> Experimental evidence that a surface acoustic wave (SAW) travelling on a (Ga,Mn)As or (Ga,Mn)(As,P) layer undergoes a resonant absortion when its frequency is matched to the precession frequency (SAW FMR, [PRB14],[JPhysConMat18]), and direct time-domain observation of the induced magnetization precession by this interaction [PRApp18]. Well chosen experimental conditions lead to the appearance of non-linearities [PRB20].

[click to enlarge]

> In this resonant configuration, experimental demonstration of SAW induced precessional switching [PRB16prec] and [JPhysConMat18], for which we had predicted the optimum conditions [PRB13]. Evidence of zero-field acoustic driven switching [PRevApp19].

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> Magnetic patterning using interfering SAWs and precessional switching [JPhysConMat18] :

[click to enlarge]

> Experimental demonstration of a large reduction of coercivity by a SAW in an out-of-plane magnetized layer, interpreted as a transient lowering of the domain-wall nucleation energy [PRB16nuc] :

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> Experimental determination of the surface acoustic wave amplitude - collab. B. Croset (INSP) et L. Largeau (C2N)

The amplitude of the acoustic wave is a crucial parameter for magnetization switching. We have therefore developed two complementary methods to estimate it : an all electrical approach [JAP17], and an X-ray diffraction approach. The acoustic wave induces the appearance of satellite diffraction peaks whose amplitude increases with the excitation power. Once correctly modeled, it yields the amplitude of the surface displacement. [JAC16]. A perfect agreement is obtained between the two techniques.

[click to enlarge]


In collaboration with B. Perrin and E. Peronne in the Acoustics for Nanosciences team, we have also excited picosecond acoustic strain wave in thin layers of GaMnAsP n and studied the resulting acousto-magneto-optical effects [PRB10]. This led to a sub-study on acoustic solitons characterization [PRB17-soliton].

++other magneto-acoustics studies done at INSP

2. Using femto-second laser pulses to manipulate magnetization

- The idea is to manipulate magnetization on time scales much shorter than those allowed by magnetic fields, and a lot more locally. For this we use a « pump-probe », time-resolved Kerr experiment relying on a femto-second laser. This allows us to follow the magnetization dynamics over a few ns after the pump pulse has triggered the magnetization precession.

1) Excitation of standing spin waves

When several spin-waves are excited, the spin stiffness constant may be extracted from the separation between frequencies [APL15].

[click to enlarge] : Typical dynamical signal obtained by time-resolved Kerr effect in GaMnAsP. The experimental curve can be decomposed into 2 oscillating signals of different frequencies (T=12 K) [APL15].


2) Detection of spin-waves : a magneto-optical illusion

The fundamental mode has a uniform amplitude across the layer thickness. That of the first excited mode is sinusoidal, and averages out to zero. It should therefore not give any magneto-optical signal. We have evidence that it is the optical phase shift felt by the light in the layer that allows it to be observed in the end. A consequence of this is the surprising experimental observation that the two modes seem to be counter-rotating [PRB17-sw].

[click to enlarge] : (a) Different modes that can be excited. (b) Dynamical reconstruction of the spin waves trajectory. A magneto-optical illusion is responsable for the apparent rotation sense.


3) Quantitative estimate of the steady-state thermal gradient

Studying linear magnetic dichroism hysteresis cycles versus temperature and pump fluence yields a quantitative determination of the stationnary temperature increase, and of its spatial gradient [JAP16].

[click to enlarge] : (a) Radial profile of the temperature rise induced by the pump (fluence 17.5 µJ/cm²) : data (symbols) and model taking into account a thermal contact resistance (full line) . (b) Analytical calculation of the radial and depth thermal profile [JAP16].


3. Domain-wall dynamics
1) Current-induced propagation : spin-transfer versus spin-orbit effects

Current-driven domain wall motion is investigated experimentally in in-plane magnetized GaMnAs tracks. The wall dynamics is found to differ in two important ways with respect to perpendicularly magnetized GaMnAs or GaMnAsP : the wall mobilities are up to ten times higher and the walls move in the same direction as the hole current. We demonstrate that these observations cannot be explained by spin orbit field torques (Rashba and Dresselhaus types) but are consistent with non-adiabatic spin transfer torque driven by the strong spin-orbit coupling of GaMnAs. This mechanism opens the way to domain wall motion driven by intrinsic (bulk) rather than interface spin-orbit interaction as in ultrathin ferromagnet/heavy metal multilayers [PRB17-dwp].

[click to enlarge] : (a) Two track configurations : current flowing parallel (perpendicular) to the easy axis. The resulting effective spin-orbit field (hollow arrow) then lies perpendicular (parallel) to the magnetization direction. (b) Current-driven domain-wall velocity : 2µm wide C// track, under field (open symbols) and 10µm wide C┴ track without field (closed symbols). (c) Three consecutive current pulses applied to a 2µm wide C// track observed under longitudinal Kerr microscopy (B=11 G, T=40K, J=24.5 GA/m²) [PRB17-dwp].


2) Propagation under field

- very high domain-wall propagation velocities (500 m/s) in in-plane magnetized GaMnAs layers [PRB12]

[click to enlarge] : Domain-wall propagation under field (in-situ micro-coil) in a 50nm out-of-plane magnetized GaMnAs layer. Longitudinal Kerr effect microscopy [PRB12]


- development of a semi-analytical model to explain velocity anomalies in out-of-plane magnetized layers : these result from the excitation of domain wall flexural modes [PRB13], [PRB11] +Highlight

collaboration with the University of Latvia and the Laboratoire de Physique des Solides (Orsay)

- domain-wall propagation in the flow regime in GaMnAs layers magnetized perpendicularly [PRB08]

3) Determination of micromagnetic parameters using Kerr microscopy

- evidence of a slight enhancement of the exchange constant in GaMnAsP following the introduction of Phosphorus [PRB10_]

- development of different methods to determine the micromagnetic parameters (exchange constant, domain-wall width) in GaMnAs/GaMnAsP using Kerr microscopy[PRB07]


Collaborations :

We collaborate with different groups on theoretical or experimental aspects :

- L. Steren and M. Tortarolo, in the framework of the LIFAN (Laboratoire International Franco-argentin en Nanosciences) : domain-wall propagation in MnAs [APL12]

- A. Cebers, University of Latvia : theoretical studies on resonance phenomena in magnetic domain-walls [PRB13]

- Teams of M. Maaref at the Institut Préparatoire aux Études Scientifiques et Technologiques in La Marsa, and K. Boujdaria at the Faculté des Sciences de Bizerte (Tunisia) : magnetic characterization of GaMnAs(P) layers [JMMM13],[JMMM15], and k.p method calculations of the magnetic parameters of GaMnAs(P) [PRB13] , [JAP12]

Recent 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. Thevenard Journal 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)

[PRB-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)

[JAP15] 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).

[Gourdon07] 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).

October 2020