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  • AIP Publishing  (7)
  • 1
    Online Resource
    Online Resource
    Pressure induced isostructural phase transition with volume expansion in DyFeO3 orthoferrite
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 122, No. 11 ( 2023-03-13)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 122, No. 11 ( 2023-03-13)
    Abstract: The orthorhombic O and O′ structure phases of ABO3-type perovskites possess the same symmetry and quite different physical properties. In this work, a pressure induced isostructural O′–O phase transition with volume expansion and less distortion in DyFeO3 orthoferrite was experimentally observed and studied by high-pressure x-ray diffraction and Raman spectroscopy measurements. Up to 35.2 GPa, DyFeO3 crystallizes in an orthorhombic Pbnm symmetry structure. With no change in the symmetry group, distinct O′-phase and O-phase were verified below 13.1 GPa and above 15.1 GPa, respectively. Meanwhile, the lattice becomes less distorted and metrically pseudo-cubic on the high-pressure side. The cell volume expands by a step in the intermediate pressure window accompanied by a decrease in spontaneous strain. It is suggested that FeO6 octahedra are more compressible than DyO12 sites under pressure. This work claimed the physical mechanism underlying phonon dynamics and variation of local structure symmetry of DyFeO3, which can be considered as the basic view for RFeO3 perovskites.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0140011
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 2
    Online Resource
    Online Resource
    Terahertz response of ultrafast spin polarization in semi-insulating GaAs
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 2 ( 2022-07-11)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 2 ( 2022-07-11)
    Abstract: Due to its high sensitivity and time-resolved ability, terahertz time-domain spectroscopy is a powerful tool for investigating ultrafast carrier dynamics in semiconductors. In addition to charges, spins of ultrafast carriers provide an alternate degree of freedom to design modern electronic devices but are rarely studied by terahertz time-domain spectroscopy. Here, ultrafast spin polarization in semi-insulating GaAs is studied by optical-pump terahertz-probe experiments at room temperature. We used circularly and linearly polarized femtosecond laser pulses to inject nonequilibrium carriers in GaAs and observed that both the transmitted and reflected terahertz signals exhibited different dynamical evolutions under the excitations of linearly and circularly polarized laser pulses, which are ascribed to the generation and relaxation of spin-polarized electrons. The lifetime of the ultrafast spin polarization was obtained from our experiments, highlighting the potentialities of terahertz spectroscopy for the investigation of spin relaxation in semiconductors.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0099739
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
    Online Resource
    Online Resource
    Structural and mechanical properties of magnesium aluminate nanoceramics under high pressure
    AIP Publishing ; 2020
    In:  Applied Physics Letters Vol. 117, No. 4 ( 2020-07-27)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 117, No. 4 ( 2020-07-27)
    Abstract: Nanoceramics may have different structural and physical properties compared to their coarse-grained counterparts. Here, we report the high-pressure study of micro- and nano-crystalline MgAl2O4 in order to examine the effect of particle size on the structural stability. A reversible pressure-induced phase transition (cubic to tetragonal) is observed in MgAl2O4 nanocrystals under non-hydrostatic pressure at room temperature, in contrast to the previously reported structural transition of MgAl2O4 at high pressure and high temperature. It is also found that the compressed MgAl2O4 microcrystals do not fracture further below 60 nm, suggesting a plastic deformation mechanism transition. MgAl2O4 with a grain size above ∼60 nm exhibits normal cracking behaviors, but shows metal-like plastic deformation behaviors below this critical size. It is implied that combined ductility and strength can be achieved in nanoceramic MgAl2O4.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0010180
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 4
    Online Resource
    Online Resource
    Electrical characteristics of normally off hydrogen-terminated diamond field effect transistors with lanthanum oxide gate dielectric
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 16 ( 2022-10-17)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 16 ( 2022-10-17)
    Abstract: A normally off hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field effect transistor (MOSFET) is realized by using lanthanum oxide (La2O3) gate dielectric. The threshold voltage is demonstrated to be −0.797 V, indicating that the La2O3-gated H-diamond MOSFET has normally off characteristics. The normally off mode could be greatly ascribed to the low work function of La2O3. Based on the capacitance–voltage (C–V) curves, the dielectric constant of La2O3 is calculated to be as high as 25.6. Moreover, the small hysteresis voltage extracted from the C–V curves exhibits low trapped charge density in the La2O3 layer. The maximum drain–source current, maximum transconductance, subthreshold swing, effective mobility, current on/off ratio, and sheet hole density of La2O3-gated MOSFET with a gate length of 2 μm are calculated to be −13.55 mA/mm, 4.37 mS/mm, 161 mV/dec, 202.2 cm2/V·s, 108, and 6.53 × 1012 cm−2, respectively. This work will significantly promote the development of normally off H-diamond MOSFET devices.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0119899
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 5
    Online Resource
    Online Resource
    Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents
    AIP Publishing ; 2013
    In:  Journal of Applied Physics Vol. 113, No. 1 ( 2013-01-07)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 113, No. 1 ( 2013-01-07)
    Abstract: Electroluminescence (EL) spectra of InGaN/GaN multiple quantum well light emitting diodes with different piezoelectric polarization fields were investigated under pulsed and direct currents. We find a positive correlation between the piezoelectric polarization field and the thermally induced red-shift of the EL spectra at high direct currents above 25 A/cm2. Under pulsed current, when thermal effects are negligible, a non-uniform EL spectrum blue-shift rate as a function of injection level is observed and compared with numerical results obtained by both self-consistent and non-self-consistent K·P methods. We conclude that the screening effect is positively related to the piezoelectric polarization field, but the band filling-induced blue-shift is almost independent from the piezoelectric field. The electrostatic fields induced by free carriers in the quantum wells increase rapidly with current but tend to saturate at higher injection where the band filling effect becomes the dominant mechanism for the blue-shift. Finally, at high injection above 30 A/cm2, an increase in Auger recombination and carrier leakage holds the spectral peaks almost constant in position.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4772683
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
    Online Resource
    Online Resource
    A skyrmion helicity-based multistate memory in synthetic antiferromagnets
    AIP Publishing ; 2022
    In:  Journal of Applied Physics Vol. 132, No. 23 ( 2022-12-21)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 132, No. 23 ( 2022-12-21)
    Abstract: Skyrmions in synthetic antiferromagnets (SAFs) are famous for being immune to the skyrmion Hall effect and hold the advantages of significantly higher speed for motion and smaller size than ferromagnetic systems. Therefore, skyrmions in SAFs are promising in spintronic devices. Here, we investigated the formation and in-plane-current-driven motion of bilayer skyrmions in the absence of Dzyaloshinskii–Moriya interaction by using micromagnetic simulations. Then, we studied the spacing variation between consecutive skyrmionic bits on the antiferromagnetic coupled nanotrack; it is found that there is an equilibrium distance between two Bloch skyrmions with opposite helicities. We also propose a reasonable method to distinguish skyrmions with opposite helicities. Finally, we displayed that the SAF skyrmion could pass through impurities due to topological protection. Based on these results, we designed the skyrmion helicity-based multistate memory devices in the SAF system, which have the advantages of high density and energy efficiency.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0130720
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 7
    Online Resource
    Online Resource
    Current-induced motion of twisted skyrmions
    AIP Publishing ; 2019
    In:  Applied Physics Letters Vol. 114, No. 19 ( 2019-05-13)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 114, No. 19 ( 2019-05-13)
    Abstract: Twisted skyrmions, whose helicity angles are different from those of Bloch and Néel skyrmions, have recently been demonstrated in experiments. In this work, we first discuss the origin and the topological properties of twisted skyrmions. Following that, we investigate the current-induced motion of twisted skyrmions by using micromagnetic simulations. It is found that the skyrmion Hall angle of twisted skyrmions driven by the spin Hall effect (SHE) varies continuously with the helicity, which means that the skyrmion Hall angle depends significantly upon the helicity in addition to the dissipative force tensor and the Gilbert damping. More importantly, we demonstrate that the trajectory of the twisted skyrmion can be controlled in a two-dimensional plane with a Gilbert damping gradient, which makes it possible to achieve the SHE-induced motion of twisted skyrmions with zero skyrmion Hall angle. At last, the simulation results demonstrate that the dynamics of twisted skyrmions driven by the spin transfer torque can be described by Thiele's equation, and they are essentially identical to the dynamics of Bloch and Néel skyrmions. Our results provide an understanding of the current-induced motion of twisted skyrmions, which may contribute to the applications of skyrmion-based racetrack memories.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.5095686
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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