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<jats:p>Single molecule magnets (SMMs) with large magnetic anisotropy energy (MAE) have great potential applications in magnetic recording. Using the first-principles calculations, we investigate the MAE of 5d transition metal–porphyrin-based SMMs by using the PBE and PBE + <jats:italic>U</jats:italic> with different <jats:italic>U</jats:italic> values, respectively. The results indicate that W–P, Re–P, Os–P, and Ir–P possess the considerably large MAE among 5d TM–P SMMs. Furthermore, the MAE of 5d TM–P can be facilely manipulated by tensile strain. The reduction of the absolute value of MAE for Ir–P molecule caused by tensile strain makes it easier to implement the writing operation. The decreasing of the occupation number of minority-spin channels of Ir-d<jats:sub> <jats:italic>x</jats:italic> <jats:sup>2</jats:sup> – <jats:italic>y</jats:italic> <jats:sup>2</jats:sup> </jats:sub> orbital leads the MAE to decrease when the tensile strain increases.</jats:p>

<jats:p>Magnetic order in two-dimensional systems was not supposed to exist at finite temperature. In recent years, the successful preparation of two-dimensional ferromagnetic materials such as CrI<jats:sub>3</jats:sub>, Cr<jats:sub>2</jats:sub>Ge<jats:sub>2</jats:sub>Te<jats:sub>6</jats:sub>, and Fe<jats:sub>3</jats:sub>GeTe<jats:sub>2</jats:sub> opens up a new chapter in the remarkable field of two-dimensional materials. Here, we report on a theoretical analysis of the stability of ferromagnetism in Fe<jats:sub>3</jats:sub>GeTe<jats:sub>2</jats:sub>. We uncover the mechanism of holding long-range magnetic order and propose a model to estimate the Curie temperature of Fe<jats:sub>3</jats:sub>GeTe<jats:sub>2</jats:sub>. Our results reveal the essential role of magnetic anisotropy in maintaining the magnetic order of two-dimensional systems. The theoretical method used here can be generalized to future research of other magnetic two-dimensional systems.</jats:p>

<jats:p>We report our nuclear magnetic resonance (NMR) study on the structurally spin chain compound Ni<jats:sub>2</jats:sub>NbBO<jats:sub>6</jats:sub> with complex magnetic coupling. The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field. The magnetic coupling configuration proposed by the first-principle density functional theory (DFT) is supported by NMR spectral analysis. For the spin dynamics, a prominent peak at <jats:italic>T</jats:italic> ∼ 35 K well above the N éel temperature (<jats:italic>T</jats:italic> <jats:sub>N</jats:sub> ∼ 20 K at <jats:italic>μ</jats:italic> <jats:sub>0</jats:sub> <jats:italic>H</jats:italic> = 10 T) is observed from the spin-lattice relaxation data. As compared with the dc-susceptibility, this behavior indicates an antiferromagnetic coupling with the typical energy scale of ∼3 meV. Thus, the Ni<jats:sub>2</jats:sub>NbBO<jats:sub>6</jats:sub> compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline <jats:italic>b</jats:italic>-axis. These facts place strong constraints on the theoretical model for this compound.</jats:p>

<jats:p>We investigate properties of perpendicular anisotropy magnetic tunnel junctions (pMTJs) with a stack structure MgO/CoFeB/Ta/CoFeB/MgO as the free layer (or recording layer), and obtain the necessary device parameters from the tunneling magnetoresistance (TMR) vs. field loops and current-driven magnetization switching experiments. Based on the experimental results and device parameters, we further estimate current-driven switching performance of pMTJ including switching time and power, and their dependence on perpendicular magnetic anisotropy and damping constant of the free layer by SPICE-based circuit simulations. Our results show that the pMTJ cells exhibit a less than 1 ns switching time and write energies &lt; 1.4 pJ; meanwhile the lower perpendicular magnetic anisotropy (PMA) and damping constant can further reduce the switching time at the studied range of damping constant <jats:italic>α</jats:italic> &lt; 0.1. Additionally, our results demonstrate that the pMTJs with the thermal stability factor ≃ 73 can be easily transformed into spin-torque nano-oscillators from magnetic memory as microwave sources or detectors for telecommunication devices.</jats:p>

<jats:p>Photoluminescence (PL) spectra of two different green InGaN/GaN multiple quantum well (MQW) samples S1 and S2, respectively with a higher growth temperature and a lower growth temperature of InGaN well layers are analyzed over a wide temperature range of 6 K–330 K and an excitation power range of 0.001 mW–75 mW. The excitation power-dependent PL peak energy and linewidth at 6 K show that in an initial excitation power range, the emission process of the MQW is dominated simultaneously by the combined effects of the carrier scattering and Coulomb screening for both the samples, and both the carrier scattering effect and the Coulomb screening effect are stronger for S2 than those for S1; in the highest excitation power range, the emission process of the MQWs is dominated by the filling effect of the high-energy localized states for S1, and by the Coulomb screening effect for S2. The behaviors can be attributed to the fact that sample S2 should have a higher amount of In content in the InGaN well layers than S1 because of the lower growth temperature, and this results in a stronger component fluctuation-induced potential fluctuation and a stronger well/barrier lattice mismatch-induced quantum-confined Stark effect. This explanation is also supported by other relevant measurements of the samples, such as temperature-dependent peak energy and excitation-power-dependent internal quantum efficiency.</jats:p>

<jats:p>The inductively coupled plasma chemical vapor deposition (ICP-CVD) deposited silicon nitride (SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub>) thin film was evaluated for its application as the electrical insulating film for a capacitor device. In order to achieve highest possible dielectric strength of SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub>, the process parameters of ICP-CVD were carefully tuned to control hydrogen in SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> films by means of tuning N<jats:sub>2</jats:sub>/SiH<jats:sub>4</jats:sub> ratio and radio frequency (RF) power. Besides electrical measurements, the hydrogen content in the films was measured by dynamic secondary ion mass spectrometry (D-SIMS). Fourier transform infrared spectroscopy (FTIR) and micro Raman spectroscopy were used to characterize the SiN<jats:sub> <jats:italic>x</jats:italic> </jats:sub> films by measuring Si–H and N–H bonds’ intensities. It was found that the more Si–H bonds lead to the higher dielectric strength.</jats:p>

<jats:p>Thanks to the quantum simulation, more and more problems in quantum mechanics which were previously inaccessible are now open to us. Capitalizing on the state-of-the-art techniques on quantum coherent control developed in past few decades, e.g., the high-precision quantum gate manipulating, the time-reversal harnessing, the high-fidelity state preparation and tomography, the nuclear magnetic resonance (NMR) system offers a unique platform for quantum simulation of many-body physics and high-energy physics. Here, we review the recent experimental progress and discuss the prospects for quantum simulation realized on NMR systems.</jats:p>

<jats:p>Tin oxide (SnO<jats:sub>2</jats:sub>) and iron-doped tin oxide (Sn<jats:sub>1 – <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub> <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>2</jats:sub>, <jats:italic>x</jats:italic> = 0.05 wt%, 0.10 wt%) nanoparticles are synthesized by the simple sol–gel method. The structural characterization using x-ray diffraction (XRD) confirms tetragonal rutile phases of the nanoparticles. The variations in lattice parameters and relative intensity with Fe-doping concentration validate the incorporation of iron into the lattice. The compressive strain present in the lattice estimated by using peak profile analysis through using Williamson–Hall plot also exhibits the influence of grain boundary formation in the lattice. The radiative recombination and quenching observed in optical characterization by using photoluminescence spectrum (PL) and the shift in the band gap estimated from UV-visible diffused reflectance spectrum corroborate the grain boundary influence. Raman spectrum and the morphological analysis by using a field emission scanning electron microscope (FESEM) also indicate the formation of grain boundaries. The compositional analysis by using energy dispersive x-ray spectrum (EDAX) confirms Fe in the SnO<jats:sub>2</jats:sub> lattice. The conductivity studies exhibit that the impendence increases with doping concentration increasing and the loss factor decreases at high frequencies with doping concentration increasing, which makes the Sn<jats:sub>1 – <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub> <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>2</jats:sub> a potential candidate for device applications.</jats:p>

<jats:p>One method of cancer therapy is to utilize nano-antenna for thermal ablation. In this method, the electromagnetic waves emitted from the nano-antenna are absorbed by the tissue and lead to heating of cancer cells. If temperature of cancer cells reaches a threshold, they will begin to die. For this purpose, an L-shaped frame nano-antenna (LSFNA) is designed to introduce into the biological tissue. Thus, the radiation characteristics of the LSFNA such as near and far-field intensities, directivity, and sensitivity to its gap width are studied to the optimization of the nano-antenna. The bio-heat and Maxwell equations are solved using the finite element method. To prevent damage to healthy tissues in this method, the antenna radiation must be completely controlled and performed carefully. Thus, penetration depth, special absorption rate, temperature distribution, and the fraction of tissue necrosis are analyzed in the biological tissue. That is why the design and optimization of the nano-antennas as a radiation source is important. Also, a pulsed source is used to excite the LSFNA. Furthermore, focusing and efficiency of the nano-antenna radiation on the cancer cell is tuned using an adjustable liquid crystal lens. The focus of this lens is changing under an electric field applied to its surrounding cathode.</jats:p>

<jats:p>A convolutional neural network is employed to retrieve the time-domain envelop and phase of few-cycle femtosecond pulses from transient-grating frequency-resolved optical gating (TG-FROG) traces. We use theoretically generated TG-FROG traces to complete supervised trainings of the convolutional neural networks, then use similarly generated traces not included in the training dataset to test how well the networks are trained. Accurate retrieval of such traces by the neural network is realized. In our case, we find that networks with exponential linear unit (ELU) activation function perform better than those with leaky rectified linear unit (LRELU) and scaled exponential linear unit (SELU). Finally, the issues that need to be addressed for the retrieval of experimental data by this method are discussed.</jats:p>