A5012179907- Magnetic properties of thin films
- ZnO doping and properties
- Magnetic and transport properties of perovskites and related materials
- Magneto-Optical Properties and Applications
- Magnetic Properties and Applications
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Multiferroics and related materials
- Ecology and Conservation Studies
- Advanced Memory and Neural Computing
- Diamond and Carbon-based Materials Research
- Electronic and Structural Properties of Oxides
- Silkworms and Sericulture Research
- Semiconductor Quantum Structures and Devices
- Theoretical and Computational Physics
- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Photonic Crystals and Applications
Hudson Institute
2016-2023
John Wiley & Sons (United States)
2016-2023
John Wiley & Sons (United Kingdom)
2016-2023
University of Oxford
2023
University of Nottingham
2012-2022
Rutherford Appleton Laboratory
2022
Czech Academy of Sciences
2022
Czech Academy of Sciences, Institute of Physics
2022
Science Oxford
2019
Bioengineering Center
2016
We study the effects of growth temperature, Ga:As ratio, and postgrowth annealing procedure on Curie temperature TC (Ga,Mn)As layers grown by molecular beam epitaxy. achieve highest values for temperatures very close to two-dimensional–three-dimensional phase boundary. The increase in TC, due removal interstitial Mn annealing, is counteracted a second process, which reduces more effective at higher temperatures. Our results show that it necessary optimize parameters obtain TC.
In a metallic ferromagnet, fast dephasing of phonons and magnons typically prevents their strong coupling. Here, the authors overcome this limitation demonstrate hybridized coherent state phonon magnon known as ``magnon polaron'' in ferromagnetic film under femtosecond optical excitation. Surface patterning provides with long lifetimes film, while spatial matching wave distributions enhances coupling strength selects particular modes broad spectra for hybridization.
Multiferroic composite materials, consisting of coupled ferromagnetic and piezoelectric phases, are great importance in the drive towards creating faster, smaller more energy efficient devices for information communications technologies. Such require thin films with large magnetostriction narrow microwave resonance linewidths. Both properties often degraded, compared to bulk due structural imperfections interface effects films. We report development epitaxial Galfenol (Fe81Ga19) as best...
Abstract The perpendicular magnetic anisotropy K eff , magnetization reversal and field-driven domain wall velocity in the creep regime are modified Pt/Co(0.85–1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. measured extraordinary Hall effect, is reduced 10 kJ/m 3 tensile out-of-plane ε z = 9 × −4 independently of film thickness, indicating a dominant volume contribution to magnetostriction. same reduces coercive field 2–4 Oe increases wide-field Kerr microscopy...
Coherent high-amplitude precession of the magnetization and spin waves with frequencies up to 40 GHz are generated by injecting picosecond compressive shear acoustic pulses into nanometer-sized galfenol (Fe81Ga19) films. The modulation is due inverse magnetostrictive effect. oscillations measured magneto-optical Kerr rotation last for several nanoseconds, maximum in-plane effective magnetic field as high mT. These results in combination a comprehensive theoretical analysis show that films...
Recent research works have shown that the magnetic order in some antiferromagnetic materials can be manipulated and detected electrically, due to two physical mechanisms: Neel-order spin-orbit torques anisotropic magnetoresistance. While these observations open up opportunities use antiferromagnets for memory devices, different characterization methods are required a better understanding of those mechanisms. Here we report field induced rotation Neel vector epitaxial tetragonal CuMnAs thin...
Ultrafast optical excitation of a metal ferromagnetic film results in modification the magnetocrystalline anisotropy and induces magnetization precession. We consider two main contributions to these processes: an effect noncoherent phonons, which modifies temperature dependent parameters coherent phonons form strain contributing via inverse magnetostriction. Contrary earlier experiments with high-symmetry structures, where mechanisms could not be separated, we study response femtosecond...
Current-induced torques in ultrathin Co/Pt bilayers were investigated using an electrically driven ferromagnetic resonance technique. The angle dependence of the resonances, detected by a rectification effect as voltage, was analysed to determine symmetries and relative magnitudes spin-orbit torques. Both anti-damping (Slonczewski) field-like observed. As ferromagnet thickness reduced from 3 1 nm, sign sum torque Oersted reversed. This observation is consistent with emergence Rashba spin...
We investigate the relationship between Curie temperature TC and carrier density p in ferromagnetic semiconductor (Ga,Mn)As. Carrier densities are extracted from analysis of Hall resistance at low temperatures high magnetic fields. Results found to be consistent with ion channeling measurements when performed on same samples. find that both electrical conductivity increase monotonically increasing p, take their largest values is comparable concentration substitutional Mn acceptors. This...
In this paper, we use simultaneous magnetometry and electrical transport measurements to critically examine ways in which the Curie temperature (TC) values have been determined studies of dilute magnetic semiconductors. We show that, sufficiently homogeneous samples, TC can be accurately from remanent magnetization susceptibility positions peak derivative resistivity. also that resistivity does not occur at TC, as illustrated by a (Ga,Mn)As sample for is 213 ± 1 K when only 178 K.
We investigate the spin polarization of ferromagnetic semiconductor (Ga,Mn)As by point-contact Andreev reflection spectroscopy. The conductance spectra are analyzed using a recent theoretical model that accounts for momentum- and spin-dependent scattering at interface. This allows us to fit data without resorting, as in case standard Blonder-Tinkham-Klapwijk (BTK) model, an effective temperature or statistical distribution superconducting gaps. find transport...
A high-amplitude microwave magnetic field localized at the nanoscale is a desirable tool for various applications within rapidly developing of nanomagnetism. Here we drive magnetization precession by coherent phonons in metal ferromagnetic nanograting and generate ac-magnetic induction with extremely high amplitude (up to 10 mT) nanometer scale localization grating grooves. We trigger laser pulse which excites surface acoustic waves. The developed technique has prospective uses several areas...
Using a time-resolved optically-pumped scanning optical microscopy technique we demonstrate the laser-driven excitation and propagation of spin waves in 20-nm film ferromagnetic metallic alloy Galfenol epitaxially grown on GaAs substrate. In contrast to previous all-optical studies employ laser-induced thermal changes magnetocrystalline anisotropy as an mechanism. A tightly focused 70-fs laser pulse excites packets magnetostatic surface with $e^{-1}$ length 3.4 $\mu$m, which is comparable...
We present an experimental investigation of the magnetic, electrical, and structural properties Ga0.94Mn0.06As1−yPy layers grown by molecular beam epitaxy on GaAs substrates for y≤0.3. X-ray diffraction measurements reveal that are under tensile strain, which gives rise to a magnetic easy axis perpendicular plane layers. The strength anisotropy coercive field increases as phosphorous concentration is increased. resistivity all samples shows metallic behavior with increasing y increases....
We present an experimental study of ultrafast optical excitation magnetostatic surface spin wave (MSSW) packets and their spectral properties in thin films pure iron. As the leave area propagate space, spectra evolve non-trivially. Particularly, low or high frequency components are suppressed at border depending on orientation external magnetic field with respect to magnetocrystalline anisotropy axes film. The effect is ascribed local heating Furthermore, time resolution implemented...
We present detailed studies of critical behavior in the strongly site-disordered dilute ferromagnetic semiconductor (Ga,Mn)As. (Ga,Mn)As has a low saturation magnetization and relatively strong magnetocrystalline anisotropy. This combination properties inhibits domain formation, thus removing principal experimental difficulty determining coefficients $\ensuremath{\beta}$ $\ensuremath{\gamma}$. find that there are still large number problems to overcome terms measurement procedures methods...
The rate and pathways of relaxation a magnetic medium to its equilibrium following excitation with intense short laser pulses are the key ingredients ultrafast optical control spins. Here we study experimentally evolution magnetization anisotropy thin films ferromagnetic metal galfenol (Fe$_{0.81}$Ga$_{0.19}$) resulting from femtosecond pulse. From temporal hysteresis loops deduce that $M_S$ parameters $K$ recover within nanosecond, ratio between satisfies thermal equilibrium's power law in...
We demonstrate a variety of precessional responses the magnetization to ultrafast optical excitation in nanolayers Galfenol (Fe,Ga), which is ferromagnetic material with large saturation and enhanced magnetostriction. The particular properties Galfenol, including cubic magnetic anisotropy weak damping, allow us detect up 6 magnon modes 120-nm layer, single mode effective damping ${\alpha}_{eff}$ = 0.005 frequency 100 GHz 4-nm layer. This highest observed date time-resolved experiments...
Electrically detected ferromagnetic resonance is measured in microdevices patterned from ultra-thin Co/Pt bilayers. Spin pumping and rectification voltages are observed distinguished via their angular dependence. The spin-pumping voltage shows an unexpected increase as the cobalt thickness reduced below 2 nm. This enhancement allows more efficient conversion of spin to charge current.
Atomic force microscopy and grazing incidence x-ray diffraction measurements have revealed the presence of ripples, aligned along [11¯0] direction on surface (Ga,Mn)As layers grown GaAs(001) substrates buffer layers, with periodicity about 50 nm in all samples that been studied. These show strong symmetry breaking uniaxial magnetic anisotropy normally observed such materials. We observe a clear correlation between amplitude ripples strength component suggesting these might be source anisotropy.
We have investigated the effects of postgrowth low temperature annealing on magnetic, electrical, and structural properties (Ga0.94Mn0.06)(As0.9P0.1) layers grown by molecular beam epitaxy. By controlling time, we are able to tune magnetic anisotropy between an easy axis in plane for as-grown samples, perpendicular fully annealed samples. The increase carrier density, as a result annealing, is found be primary reason sign reversal anisotropy, qualitative agreement with theoretical predictions.
We demonstrate a strong dependence of the anisotropic magnetoresistance (AMR) on direction current with respect to crystalline axes in quaternary diluted ferromagnetic semiconductor Ga0.94Mn0.06As0.9Sb0.1. Dominant cubic and uniaxial symmetries are observed for along [11¯0] [110] directions, respectively. In addition, an anomalous temperature symmetry magnitude AMR is observed. Phenomenological analysis reveals important contribution crossed crystalline/non-crystalline term, which much...
We have studied in-plane anisotropic magnetoresistance (AMR) in cobalt films with overlayers having designed electrically interface transparency. With an opaque cobalt/overlayer interface, the AMR ratio is shown to vary inverse proportion film thickness; indication that a consequence of scattering both volume and interfacial contributions. The anisotropy opposes contribution, causing diminish as thickness reduced. An intrinsic effect explains significantly reduced ultra-thin films.
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation A. Casiraghi, W. Rushforth, J. Zemen, Haigh, M. Wang, K. Edmonds, R. P. Campion, B. L. Gallagher; Piezoelectric strain induced variation of the magnetic anisotropy in a high Curie temperature (Ga,Mn)As sample. Appl. Phys. Lett. 20 August 2012; 101 (8): 082406. https://doi.org/10.1063/1.4746250 Download citation...