scholarly journals Ultrafast Modulation of Magnetization Dynamics in Ferromagnetic (Ga, Mn)As Thin Films

2018 ◽  
Vol 8 (10) ◽  
pp. 1880 ◽  
Author(s):  
Hang Li ◽  
Xinhui Zhang ◽  
Xinyu Liu ◽  
Margaret Dobrowolska ◽  
Jacek Furdyna
Keyword(s):  
Magnetic Anisotropy ◽  
Spin Dynamics ◽  
Optical Excitation ◽  
Laser Pulses ◽  
Time Resolved ◽  
Ultrafast Optical ◽  
Optical Effects ◽  
Out Of Plane ◽  
Linearly Polarized ◽  
Magnetization Precession

Magnetization precession induced by linearly polarized optical excitation in ferromagnetic (Ga,Mn)As was studied by time-resolved magneto-optical Kerr effect measurements. The superposition of thermal and non-thermal effects arising from the laser pulses complicates the analysis of magnetization precession in terms of magnetic anisotropy fields. To obtain insight into these processes, we investigated compressively-strained thin (Ga,Mn)As films using ultrafast optical excitation above the band gap as a function of pulse intensity. Data analyses with the gyromagnetic calculation based on Landau-Lifshitz-Gilbert equation combined with two different magneto-optical effects shows the non-equivalent effects of in-plane and out-of-plane magnetic anisotropy fields on both the amplitude and the frequency of magnetization precession, thus providing a handle for separating the effects of non-thermal and thermal processes in this context. Our results show that the effect of photo-generated carriers on magnetic anisotropy constitutes a particularly effective mechanism for controlling both the frequency and amplitude of magnetization precession, thus suggesting the possibility of non-thermal manipulation of spin dynamics through pulsed laser excitations.

Control of coherent magnetization precession in GaMnAs by ultrafast optical excitation

2008 ◽  
Vol 5 (8) ◽  
pp. 2637-2640 ◽  
Author(s):  
J. Qi ◽  
Y. Xu ◽  
X. Liu ◽  
J. K. Furdyna ◽  
I. E. Perakis ◽  
...  
Keyword(s):  
Optical Excitation ◽  
Ultrafast Optical ◽  
Magnetization Precession

Time-resolved thermal expansion of an STM tip after ultrafast optical excitation

1998 ◽  
Author(s):  
R. Huber ◽  
M. Koch ◽  
M. Perner ◽  
W. Spirkl ◽  
J. Feldmann
Keyword(s):  
Thermal Expansion ◽  
Optical Excitation ◽  
Time Resolved ◽  
Ultrafast Optical

scholarly journals Ultrafast and Distinct Spin Dynamics in Magnetic Alloys

SPIN ◽  
2015 ◽  
Vol 05 (03) ◽  
pp. 1550004 ◽  
Author(s):  
I. Radu ◽  
C. Stamm ◽  
A. Eschenlohr ◽  
F. Radu ◽  
R. Abrudan ◽  
...  
Keyword(s):  
Exchange Interaction ◽  
Data Storage ◽  
Magnetic Circular Dichroism ◽  
Dynamic Properties ◽  
Spin Dynamics ◽  
Magnetic Moments ◽  
Dynamical Behavior ◽  
Laser Pulses ◽  
Time Resolved ◽  
Fs Laser

Controlling magnetic order on ultrashort timescales is crucial for engineering the next-generation magnetic devices that combine ultrafast data processing with ultrahigh-density data storage. An appealing scenario in this context is the use of femtosecond (fs) laser pulses as an ultrafast, external stimulus to fully set the orientation and the magnetization magnitude of a spin ensemble. Achieving such control on ultrashort timescales, e.g., comparable to the excitation event itself, remains however a challenge due to the lack of understanding the dynamical behavior of the key parameters governing magnetism: The elemental magnetic moments and the exchange interaction. Here, we investigate the fs laser-induced spin dynamics in a variety of multi-component alloys and reveal a dissimilar dynamics of the constituent magnetic moments on ultrashort timescales. Moreover, we show that such distinct dynamics is a general phenomenon that can be exploited to engineer new magnetic media with tailor-made, optimized dynamic properties. Using phenomenological considerations, atomistic modeling and time-resolved X-ray magnetic circular dichroism (XMCD), we demonstrate demagnetization of the constituent sub-lattices on significantly different timescales that depend on their magnetic moments and the sign of the exchange interaction. These results can be used as a “recipe” for manipulation and control of magnetization dynamics in a large class of magnetic materials.

scholarly journals Rippling ultrafast dynamics of suspended 2D monolayers, graphene

2016 ◽  
Vol 113 (43) ◽  
pp. E6555-E6561 ◽  
Author(s):  
Jianbo Hu ◽  
Giovanni M. Vanacore ◽  
Andrea Cepellotti ◽  
Nicola Marzari ◽  
Ahmed H. Zewail
Keyword(s):  
Time Scale ◽  
Negative Thermal Expansion ◽  
Early Time ◽  
Optical Excitation ◽  
Atomic Scale ◽  
Monolayer Graphene ◽  
Phonon Modes ◽  
Ultrafast Optical ◽  
Out Of Plane ◽  
Deformation Dynamics

Here, using ultrafast electron crystallography (UEC), we report the observation of rippling dynamics in suspended monolayer graphene, the prototypical and most-studied 2D material. The high scattering cross-section for electron/matter interaction, the atomic-scale spatial resolution, and the ultrafast temporal resolution of UEC represent the key elements that make this technique a unique tool for the dynamic investigation of 2D materials, and nanostructures in general. We find that, at early time after the ultrafast optical excitation, graphene undergoes a lattice expansion on a time scale of 5 ps, which is due to the excitation of short-wavelength in-plane acoustic phonon modes that stretch the graphene plane. On a longer time scale, a slower thermal contraction with a time constant of 50 ps is observed and associated with the excitation of out-of-plane phonon modes, which drive the lattice toward thermal equilibrium with the well-known negative thermal expansion coefficient of graphene. From our results and first-principles lattice dynamics and out-of-equilibrium relaxation calculations, we quantitatively elucidate the deformation dynamics of the graphene unit cell.

scholarly journals Photocharging dynamics in colloidal CdS quantum dots visualized by electron spin coherence

2018 ◽  
Vol 52 (4) ◽  
pp. 489
Author(s):  
D.R. Yakovlev ◽  
D.H. Feng ◽  
V.V. Pavlov ◽  
A.V. Rodina ◽  
E.V. Shornikova ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Spin Dynamics ◽  
Surface States ◽  
Laser Pulses ◽  
Spin Coherence ◽  
Core Electron ◽  
Time Resolved ◽  
Hole Trapping ◽  
Colloidal Cds

AbstractWe use a time-resolved technique with three laser pulses (pump, orientation and probe) to study the photocharging dynamics with picosecond resolution on a long timescale ranging from ps to ms in CdS colloidal quantum dots. The detection is based on measuring the coherent spin dynamics of electrons, allowing us to distinguish the type of carrier in the dot core (electron or hole). We find that although initially negative photocharging happens because of fast hole trapping on surface states, eventually it evolves to positive photocharging due to electron trapping and hole detrapping. The positive photocharging lasts up to hundreds of microseconds at room temperature.

Time-resolved spin dynamics in diluted magnetic semiconductor quantum wells

1990 ◽  
Vol 68 (9) ◽  
pp. 726-727 ◽  
Author(s):  
M. R. Freeman ◽  
D. D. Awschalom
Keyword(s):  
Quantum Wells ◽  
Spin Polarization ◽  
Diluted Magnetic Semiconductor ◽  
Spin Dynamics ◽  
Magnetic Semiconductor ◽  
Laser Pulses ◽  
Initial Energy ◽  
Ultrashort Laser Pulses ◽  
Time Resolved ◽  
Diluted Magnetic

Ultrashort laser pulses were used to prepare charge-carrier populations of known initial energy and spin polarization in two-dimensional quantum wells of the diluted magnetic semiconductor Cd1−xMnxTe. The evolutions of the carrier spin polarization and of magnetization transferred to the magnetic ions were observed using time-resolved optical techniques.

Control of coherent magnetization precession in GaMnAs by ultrafast optical excitation

2007 ◽  
Author(s):  
J. Qi ◽  
Y. Xu ◽  
X. Liu ◽  
J. K. Furdyna ◽  
I. E. Perakis ◽  
...  
Keyword(s):  
Optical Excitation ◽  
Ultrafast Optical ◽  
Magnetization Precession

scholarly journals Coherent magnetization precession in GaMnAs induced by ultrafast optical excitation

2007 ◽  
Vol 91 (11) ◽  
pp. 112506 ◽  
Author(s):  
J. Qi ◽  
Y. Xu ◽  
N. H. Tolk ◽  
X. Liu ◽  
J. K. Furdyna ◽  
...  
Keyword(s):  
Optical Excitation ◽  
Ultrafast Optical ◽  
Magnetization Precession

scholarly journals Experimental realization of linearly polarized X-ray detected ferromagnetic resonance

2021 ◽  
Author(s):  
Christoph Klewe ◽  
Satoru Emori ◽  
Qian Li ◽  
Mengmeng Yang ◽  
Benjamin A. Gray ◽  
...  
Keyword(s):  
Ferromagnetic Resonance ◽  
Spin Dynamics ◽  
Linear Dichroism ◽  
Fourier Component ◽  
Time Resolved ◽  
Experimental Realization ◽  
X Ray ◽  
Linearly Polarized ◽  
Magnetic Linear Dichroism ◽  
Harmonic Components

Abstract We present the first theoretical and experimental evidence of time-resolved dynamic X-ray magnetic linear dichroism (XMLD) measurements of GHz magnetic precessions driven by ferromagnetic resonance in both metallic and insulating thin films. Our findings show a dynamic XMLD in both ferromagnetic Ni80Fe20 and ferrimagnetic Ni0.65Zn0.35Al0.8Fe1.2O4 for different measurement geometries and linear polarizations. A detailed analysis of the observed signals reveals the importance of separating different harmonic components in the dynamic signal in order to identify the XMLD response without the influence of competing contributions. In particular, RF magnetic resonance elicits a large dynamic XMLD response at the fundamental frequency under experimental geometries with oblique x-ray polarization. The geometric range and experimental sensitivity can be improved by isolating the 2ω Fourier component of the dynamic response.These results illustrate the potential of dynamic XMLD and represent a milestone accomplishment towards the study of GHz spin dynamics in systems beyond ferromagnetic order.

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