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<jats:p>Using the first-principles calculations, we study the structural, electronic, and magnetic properties along with exchange interactions and Curie temperatures for CrZrCo<jats:italic>Z</jats:italic> (<jats:italic>Z</jats:italic> = Al, Ga, In, Tl, Si, Pb) quaternary Heusler alloys. The results show that the CrZrCo<jats:italic>Z</jats:italic> alloys are half-metallic ferrimagnets, and their total spin magnetic moments, which are mainly carried by the Cr atom, obey the Slater–Pauling rule. Analysis of local density of states confirms that the exchange splitting between e<jats:sub>g</jats:sub> and t<jats:sub>2g</jats:sub> states leads to the formation of half-metallic gap. According to the calculated Heisenberg exchange coupling parameters, it is found that the Cr(A)–Cr(A) and Cr(A)–Zr(B) exchanges dominate the appearance of ferrimagnetic states in CrZrCo<jats:italic>Z</jats:italic> (<jats:italic>Z</jats:italic> = Al, Ga, In, Tl, Pb) alloys, and it is the Cr(A)–Zr(B) and Zr(B)–Zr(B) exchanges for CrZrCoSi alloy. Finally, we estimate the Curie temperatures of CrZrCo<jats:italic>Z</jats:italic> by using mean-field approximation, it is found that the CrZrCo<jats:italic>Z</jats:italic> (<jats:italic>Z</jats:italic> = Al, Ga, In, Tl, Pb) alloys have noticeably higher Curie temperatures than room temperature. So, we expect that the CrZrCo<jats:italic>Z</jats:italic> alloys are promising candidates in spintronic applications in future.</jats:p>

<jats:p>Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material. The control of carrier lifetime is the key to optimizing the device function by tuning the electro–optical conversion quantum yield, carrier diffusion length, carrier collection process, <jats:italic>etc</jats:italic>. Till now, the prevailing modulation methods are mainly by defect engineering and temperature control, which have limitations in the modulation direction and amplitude of the carrier lifetime. Here, we report an effective modulation on the ultrafast dynamics of photoexcited carriers in two-dimensional (2D) MoS<jats:sub>2</jats:sub> monolayer by uniaxial tensile strain. The combination of optical ultrafast pump–probe technique and time-resolved photoluminescence (PL) spectroscopy reveals that the carrier dynamics through Auger scattering, carrier–phonon scattering, and radiative recombination keep immune to the strain. But strikingly, the uniaxial tensile strain weakens the trapping of photoexcited carriers by defects and therefore prolongs the corresponding carrier lifetime up to 440% per percent applied strain. Our results open a new avenue to enlarge the carrier lifetime of 2D MoS<jats:sub>2</jats:sub>, which will facilitate its applications in high-efficient optoelectronic and photovoltaic devices.</jats:p>

<jats:p>We study the behaviors of three-dimensional double and triple Weyl fermions in the presence of weak random potential. By performing the Wilsonian renormalization group (RG) analysis, we reveal that the quasiparticle experiences strong renormalization which leads to the modification of the density of states and quasiparticle residue. We further utilize the RG analysis to calculate the classical conductivity and show that the diffusive transport is substantially corrected due to the novel behavior of the quasiparticle and can be directly measured by experiments.</jats:p>

<jats:p>We propose an interferometer composing of a scanning tunneling microscope (STM), double quantum dots (DQDs), and a semiconductor nanowire carrying Majorana bound states (MBSs) at its ends induced by the proximity effect of an s-wave superconductor, to probe the existence of the MBSs in the dots. Our results show that when the energy levels of DQDs are aligned to the energy of MBSs, the zero-energy spectral functions of DQDs are always equal to 1/2, which indicates the formation of the MBSs in the DQDs and is also responsible for the zero-bias conductance peak. Our findings suggest that the spectral functions of the DQDs may be an excellent and convenient quantity for detecting the formation and stability of the spatially separated MBSs in quantum dots.</jats:p>

<jats:p>Strain and stress were simulated using finite element method (FEM) for three III–V-on-Insulator (III–VOI) structures, <jats:italic>i.e.</jats:italic>, InP/SiO<jats:sub>2</jats:sub>/Si, InP/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/SiO<jats:sub>2</jats:sub>/Si, and GaAs/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/SiO<jats:sub>2</jats:sub>/Si, fabricated by ion-slicing as the substrates for optoelectronic devices on Si. The thermal strain/stress imposes no risk for optoelectronic structures grown on InPOI at a normal growth temperature using molecular beam epitaxy. Structures grown on GaAsOI are more dangerous than those on InPOI due to a limited critical thickness. The intermedia Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> layer was intended to increase the adherence while it brings in the largest risk. The simulated results reveal thermal stress on Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> over 1 GPa, which is much higher than its critical stress for interfacial fracture. InPOI without an Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> layer is more suitable as the substrate for optoelectronic integration on Si.</jats:p>

<jats:p>The in-plane magnetotransport of detwinned EuFe<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub> single crystal has been investigated. In the antiferromagnetic phase of Eu<jats:sup>2+</jats:sup> spins, very different magnetoresistance results are observed upon the change of the external magnetic field direction and the current direction. This could be attributed to the tunable orientation of the Eu<jats:sup>2+</jats:sup> spins under magnetic field. Electron scattering by spin fluctuation, superzone boundary effect, and cyclotron motion of charge carriers are used to interpret the observed anomalous magnetoresistance which is measured by using a current along <jats:italic>a</jats:italic> direction. The remarkable features of magnetoresistance suggest that itinerant electrons strongly couple with the spin configuration of Eu<jats:sup>2+</jats:sup>, which has a huge influence on the transport properties of EuFe<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub>.</jats:p>

<jats:p>Rare-earth (<jats:italic>R</jats:italic>)-based materials with large reversible magnetocaloric effect (MCE) are attracting much attention as the promising candidates for low temperature magnetic refrigeration. In the present work, the magnetic properties and MCE of DyNiGa compound with TiNiSi-type orthorhombic structure are studied systematically. The DyNiGa undergoes a magnetic transition from antiferromagnetic (AFM) to paramagnetic state with Néel temperature <jats:italic>T</jats:italic> <jats:sub>N</jats:sub> = 17 K. Meanwhile, it does not show thermal and magnetic hysteresis, revealing the perfect thermal and magnetic reversibility. Moreover, the AFM state can be induced into a ferromagnetic state by a relatively low field, and thus leading to a large reversible MCE, <jats:italic>e.g.</jats:italic>, a maximum magnetic entropy change (−Δ<jats:italic>S</jats:italic> <jats:sub>M</jats:sub>) of 10 J/kg⋅K is obtained at 18 K under a magnetic field change of 5 T. Consequently, the large MCE without thermal or magnetic hysteresis makes the DyNiGa a competitive candidate for magnetic refrigeration of hydrogen liquefaction.</jats:p>

<jats:p>Based on the uniform, helical and spiral domain-wall magnetic configurations, the excited spin waves are studied with emphasis on the role of damping. We find that the damping closes the gap of dispersion, and greatly influences the dispersion in the long-wave region for the spin waves of spiral wall and helical structure. For the uniform configuration, the Dzyaloshinskii–Moriya interaction determines the modification of dispersion by the damping. Furthermore, we investigate the interaction between spin waves and a moving spiral domain wall. In the presence of damping, the amplitude of spin wave can increase after running across the wall for small wave numbers. Driving by the spin waves, the wall propagates towards the spin-wave source with an increasing velocity. Unlike the case without damping, the relation between the wall velocity and the spin-wave frequency depends on the position of wall.</jats:p>

<jats:p>The electronic and magnetic properties of strontium hexa-ferrite (SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub>) are studied in pure state (SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub>) and with dopant in the positions 2 and 3 of Fe atoms (SrGdFe<jats:sub>11</jats:sub>O<jats:sub>19</jats:sub>-I and SrGdFe<jats:sub>11</jats:sub>O<jats:sub>19</jats:sub>-II, respectively) by utilizing a variety of the density functional theory (DFT) approaches including the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and GGA plus Hubbard <jats:italic>U</jats:italic> parameter (GGA+<jats:italic>U</jats:italic>). The pure SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub> is a hard magnetic half-metal with an integer magnetic moment of 64.00<jats:italic>μ</jats:italic> <jats:sub>B</jats:sub>, while using the GGA+<jats:italic>U</jats:italic> functional, the magnetic intensity increases, resulting in a magnetic semiconductor with a high integer magnetic moment of 120<jats:italic>μ</jats:italic> <jats:sub>B</jats:sub>. By doping the Gd atom in the two different positions of Fe, the magnetic moment is increased to 71.68<jats:italic>μ</jats:italic> <jats:sub>B</jats:sub> and 68.00<jats:italic>μ</jats:italic> <jats:sub>B</jats:sub>, respectively. The magnetic moment increases and remains an integer; hence, SrGdFe<jats:sub>11</jats:sub>O<jats:sub>19</jats:sub>-II can be very useful for application in magnetic memories. Moreover, applying the Hubbard parameter turns SrGdFe<jats:sub>11</jats:sub>O<jats:sub>19</jats:sub>-I and SrGdFe<jats:sub>11</jats:sub>O<jats:sub>19</jats:sub>-II to magnetic semiconductors with a magnetic moment of 124<jats:italic>μ</jats:italic> <jats:sub>B</jats:sub>, and the energy gap of both doped structures at spin down is found to be less than the pure case. By studying the electronic density diagram of the atoms of the crystal, it is found that the major effect to create magnetization in the pure case is due to the Fe atom. However, in the doped case, the elements Gd and Fe have the highest moment in the crystal respectively.</jats:p>

<jats:p>We establish a theoretical bimodal model for the complex permeability of flaky soft magnetic composite materials to explain the variability of their initial permeability. The new model is motivated by finding the two natural resonance peaks to be inconsistent with the combination of the domain wall resonance and the natural resonance. In the derivation of the model, two relationships are explored: the first one is the relationship between the number of magnetic domains and the permeability, and the second one is the relationship between the natural resonance and the domain wall resonance. This reveals that the ball milling causes the number of magnetic domains to increase and the maximum initial permeability to exist after 10 h of ball milling. An experiment is conducted to demonstrate the reliability of the proposed model. The experimental results are in good agreement with the theoretical calculations. This new model is of great significance for studying the mechanism and applications of the resonance loss for soft magnetic composite materials in high frequency fields.</jats:p>