scholarly journals Photoinduced spin dynamics in a uniaxial intermetallic heterostructure $$\hbox {TbCo}_2/\hbox {FeCo}$$

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Sergei Ovcharenko ◽  
Mikhail Gaponov ◽  
Alexey Klimov ◽  
Nicolas Tiercelin ◽  
Philippe Pernod ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Dynamics ◽  
Thermal Relaxation ◽  
Optical Excitation ◽  
Initial Position ◽  
Light Polarization ◽  
Spin Reorientation ◽  
Maximum Deviation ◽  
Polarization Rotation ◽  
The Time Domain

Abstract Intermetallic heterostructures of rare-earth and transition metals exhibit physical properties prospective for various applications. These structures combine giant magnetostriction, controllable magnetic anisotropy, magneto-optical activity and allow spin reorientation transitions (SRT) induced by magnetic field at room temperature. Here, we present the results of a study of spin dynamics induced by ultrafast optical excitation in the $$\hbox {TbCo}_2\hbox {/FeCo}$$ TbCo 2 /FeCo heterostructure. The time dependence of the light polarization rotation excited by a pump optical pulse with a duration of 35 fs was measured in the total range of the SRT created by external DC magnetic field. We found hysteretic dependence of the polarization rotation on magnetizing field that is specific for spin dynamics near SRT. Enhancement of the rotation is observed in the critical points of the SRT and near the points of magnetization switch from metastable to stable spin states. In the time-domain, two characteristic delays of 20 ps and 200 ps were found, corresponding to the maximum deviation of the light polarization after excitation. The first is explained by the precession motion of spins out of the plane of the structure. The latter is accounted for the spin in-plane deviation from its initial position and thermal relaxation of the anisotropy.

scholarly journals Dynamics of frequency-swept nuclear spin optical pumping in powdered diamond at low magnetic fields

2019 ◽  
Vol 116 (7) ◽  
pp. 2512-2520 ◽  
Author(s):  
Pablo R. Zangara ◽  
Siddharth Dhomkar ◽  
Ashok Ajoy ◽  
Kristina Liu ◽  
Raffi Nazaryan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Optical Pumping ◽  
Spin Dynamics ◽  
Optical Excitation ◽  
Microwave Frequency ◽  
Sweep Rate ◽  
Nitrogen Vacancy ◽  
Diamond Surface

A broad effort is underway to improve the sensitivity of NMR through the use of dynamic nuclear polarization. Nitrogen vacancy (NV) centers in diamond offer an appealing platform because these paramagnetic defects can be optically polarized efficiently at room temperature. However, work thus far has been mainly limited to single crystals, because most polarization transfer protocols are sensitive to misalignment between the NV and magnetic field axes. Here we study the spin dynamics of NV−13C pairs in the simultaneous presence of optical excitation and microwave frequency sweeps at low magnetic fields. We show that a subtle interplay between illumination intensity, frequency sweep rate, and hyperfine coupling strength leads to efficient, sweep-direction-dependent 13C spin polarization over a broad range of orientations of the magnetic field. In particular, our results strongly suggest that finely tuned, moderately coupled nuclear spins are key to the hyperpolarization process, which makes this mechanism distinct from other known dynamic polarization channels. These findings pave the route to applications where powders are intrinsically advantageous, including the hyperpolarization of target fluids in contact with the diamond surface or the use of hyperpolarized particles as contrast agents for in vivo imaging.

scholarly journals Suppression of nuclear spin fluctuations in an InGaAs quantum dot ensemble by GHz-pulsed optical excitation

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
E. Evers ◽  
N. E. Kopteva ◽  
I. A. Yugova ◽  
D. R. Yakovlev ◽  
D. Reuter ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Nuclear Spin ◽  
Spin Dynamics ◽  
Optical Excitation ◽  
Transverse Magnetic ◽  
Repetition Frequency ◽  
Spin Fluctuations ◽  
Optical Transitions ◽  
Singly Charged ◽  
Electron Spin Dynamics

AbstractThe coherent electron spin dynamics of an ensemble of singly charged (In,Ga)As/GaAs quantum dots in a transverse magnetic field is driven by periodic optical excitation at 1 GHz repetition frequency. Despite the strong inhomogeneity of the electron g factor, the spectral spread of optical transitions, and the broad distribution of nuclear spin fluctuations, we are able to push the whole ensemble of excited spins into a single Larmor precession mode that is commensurate with the laser repetition frequency. Furthermore, we demonstrate that an optical detuning of the pump pulses from the probed optical transitions induces a directed dynamic nuclear polarization and leads to a discretization of the total magnetic field acting on the electron ensemble. Finally, we show that the highly periodic optical excitation can be used as universal tool for strongly reducing the nuclear spin fluctuations and preparation of a robust nuclear environment for subsequent manipulation of the electron spins, also at varying operation frequencies.

scholarly journals Polarization control of THz emission using spin-reorientation transition in spintronic heterostructure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dinar Khusyainov ◽  
Sergei Ovcharenko ◽  
Mikhail Gaponov ◽  
Arseniy Buryakov ◽  
Alexey Klimov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Electromagnetic Waves ◽  
Light Emission ◽  
Light Polarization ◽  
Spin Reorientation ◽  
Easy Magnetization ◽  
Polarization Control ◽  
Spin Reorientation Transition

AbstractPolarization of electromagnetic waves plays an extremely important role in interaction of radiation with matter. In particular, interaction of polarized waves with ordered matter strongly depends on orientation and symmetry of vibrations of chemical bonds in crystals. In quantum technologies, the polarization of photons is considered as a “degree of freedom”, which is one of the main parameters that ensure efficient quantum computing. However, even for visible light, polarization control is in most cases separated from light emission. In this paper, we report on a new type of polarization control, implemented directly in a spintronic terahertz emitter. The principle of control, realized by a weak magnetic field at room temperature, is based on a spin-reorientation transition (SRT) in an intermetallic heterostructure TbCo2/FeCo with uniaxial in-plane magnetic anisotropy. SRT is implemented under magnetic field of variable strength but of a fixed direction, orthogonal to the easy magnetization axis. Variation of the magnetic field strength in the angular (canted) phase of the SRT causes magnetization rotation without changing its magnitude. The charge current excited by the spin-to-charge conversion is orthogonal to the magnetization. As a result, THz polarization rotates synchronously with magnetization when magnetic field strength changes. Importantly, the radiation intensity does not change in this case. Control of polarization by SRT is applicable regardless of the spintronic mechanism of the THz emission, provided that the polarization direction is determined by the magnetic moment orientation. The results obtained open the prospect for the development of the SRT approach for THz emission control.

INFLUENCE OF AN EXTERNAL MAGNETIC FIELD ON THE DYNAMICS OF A NEW-PHASE NUCLEUS IN THE VICINITY OF THE FIRST-ORDER PHASE TRANSITION IN MAGNETS WITH DEFECTS PRESENT

2012 ◽  
Vol 26 (28) ◽  
pp. 1250183 ◽  
Author(s):  
VLADIMIR NAZAROV ◽  
RISHAT SHAFEEV
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
External Magnetic Field ◽  
Magnetic Anisotropy ◽  
Spin Reorientation ◽  
Critical Fields ◽  
First Order ◽  
Phase Nucleus ◽  
First Order Phase Transition ◽  
New Phase

Theoretically, with the aid of a soliton model, the evolution of a new-phase nucleus near the first-order spin-reorientation phase transition in magnets has been investigated in an external magnetic field. The influence of an external field and one-dimensional defects of magnetic anisotropy on the dynamics of such nucleus has been demonstrated. The conditions for the localization of the new-phase nucleus in the region of the magnetic anisotropy defect and for its escape from the defect have been determined. The values of the critical fields which bring about the sample magnetization reversal have been identified and estimated.

MAGNETOSTATIC MODES IN NANOMETER-SIZED FERROMAGNETIC AND ANTIFERROMAGNETIC TUBES

2007 ◽  
Vol 14 (03) ◽  
pp. 471-480 ◽  
Author(s):  
T. K. DAS ◽  
M. G. COTTAM
Keyword(s):  
Magnetic Field ◽  
Spin Dynamics ◽  
Continuum Theory ◽  
Inelastic Light Scattering ◽  
Dipole Interactions ◽  
Large Length ◽  
Magnetostatic Modes ◽  
Magnetostatic Spin Waves ◽  
Macroscopic Continuum ◽  
Cylindrical Axis

A theory is presented for the magnetostatic modes in ferromagnetic and antiferromagnetic nanotubes, which have a large length-to-radius aspect ratio and an external magnetic field parallel to the cylindrical axis. The surface and bulk magnetic excitations (or magnetostatic spin waves) are studied for cases where the dipole–dipole interactions are dominant in the spin dynamics. This situation can be realized at sufficiently small wavevectors by inelastic light scattering or magnetic resonance techniques. A macroscopic continuum theory is developed, using the magnetostatic form of Maxwell's equations and the electromagnetic boundary conditions, and the characteristic equations (or dispersion relations) are deduced for the magnetostatic modes. Numerical calculations are presented for ferromagnetic and antiferromagnetic nanostructures, taking Ni 80 Fe 20 and MnF 2, respectively. The spatial variations of the mode amplitudes are also investigated.

Spin reorientation and magnetoelastic coupling in Nd/sub 2/CuO/sub 4/ in external magnetic field

1993 ◽  
Vol 29 (6) ◽  
pp. 3240-3242
Author(s):  
V.L. Sobolev ◽  
H.L. Huang ◽  
I.M. Vitebskii ◽  
A.N. Knigavko ◽  
Y.G. Pashkevich
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Spin Reorientation ◽  
Magnetoelastic Coupling

Magnetic ground state of low-doped manganites probed by spin dynamics under magnetic field

2004 ◽  
Vol 272-276 ◽  
pp. 1784-1786 ◽  
Author(s):  
P. Kober ◽  
M. Hennion ◽  
F. Moussa ◽  
A. Ivanov ◽  
L.-P. Regnault ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Ground State ◽  
Spin Dynamics ◽  
Magnetic Ground State ◽  
Doped Manganites

scholarly journals Spin transport and spin dynamics in antiferromagnets

2021 ◽  
Author(s):  
◽  
Geert Hoogeboom
Keyword(s):  
Magnetic Field ◽  
Heavy Metal ◽  
Spin Transport ◽  
Spin Dynamics ◽  
Magnetic Moments ◽  
Spin Current ◽  
Active Role ◽  
Metal Films ◽  
Alternating Direction ◽  
High Processing

Ferromagnets (FMs) have been a key ingredient in information technology because it is easy to manipulate and read out the magnetization. Antiferromagnets (AFMs) have magnetic moments with alternating direction resulting in negligible magnetization. This gives them high processing and device downscaling features, but this also makes it challenging to manipulate and interact with the AFM order. This thesis studies this interaction with antiferromagnets. NiO AFM order has been read out by electrically injecting spin current via the spin Hall effect in thin heavy metal films. In DyFeO3, both Dy and Fe magnetic moments, their excitation and interaction have been probed. A magnetic field lifts the degeneracy of magnetic excitations with opposite magnon spin, allowing a spin current to be detected nonlocally. The AFM order and the generation of spin current can easily be controlled by an adjacent FM. Thereby, we show that AFMs have the potential to play an active role in spintronics.

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