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We present a study on the development of Finnish first-year physics majors' attitudes towards physics, as measured by the Colorado Learning Attitudes about Science Survey, before, during, and after the period of mandatory remote learning due to the coronavirus pandemic. We find that in the years before the pandemic, these attitudes did not change, but the period of extended remote learning due to the pandemic had a negative effect on the students' expertlike views. Similarly, the students who experienced the remote learning period in high school displayed a lower level of expertlike thinking as they entered university. As contact teaching resumed, moderate positive gains were seen, bridging some but not all of the gap in student attitudes left by the pandemic.

Harnessing the full power of memristors as artificial synapses demands a simple and scalable crossbar architecture enabling their seamless integration into diverse applications. This Letter presents the 3 × 3 memristor crossbar array configuration featuring a grid of interconnected devices. The composition includes Al as the reactive top electrode connecting the device columns and Gd1−xCaxMnO3 (GCMO, x = 0.8) serving as the bottom electrode connecting the device rows as well as the memristive material eliminating the need for additional layers and fabrication steps. Controlled-sized vias through insulating the Al2O3 layer connect the electrodes forming the active interface. The idea is validated with a test sample of 3 × 3 crossbars with the Au/GCMO/Al structure, Au enabling Ohmic contact to GCMO, with device resistive switching ratios mostly around 102 and yield of over 90%. The devised crossbar structure could provide a highly scalable, yet simple, geometry suitable for synaptic networks. [ABSTRACT FROM AUTHOR]

A set of low-cost monometallic Fe, Ni, and bimetallic Fe–Ni bifunctional H–Y-5.1 catalysts with different metal ratios were synthesized by sequential incipient wetness impregnation. The catalysts were characterized in detail by N2 physisorption, Fourier transform infrared spectroscopy with pyridine, inductively coupled plasma optical emission spectroscopy, X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM–SEM), magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy, magnetic measurements, temperature-programmed reduction (TPR), and X-ray absorption spectroscopy (XAS). The results revealed that introduction of Fe led to a decrease of strong acid sites and an increase of medium Brønsted acid sites, while introduction of Ni increased the number of Lewis acid sites. The particle size of iron was approx. 5 nm, being ca. fourfold higher for nickel. XPS demonstrated higher iron content on the catalyst surface compared to nickel. Both Mössbauer spectroscopy and magnetic measurement confirmed the ferromagnetic behavior of all catalysts. In addition, the results from XRD, TEM, XPS, XAS, and magnetization suggested strong Fe–Ni nanoparticle interactions, which were supported by modeling of TPR profiles. Catalytic results of the co-processing of fossil feedstock with lignin-derived isoeugenol clearly showed that both product distribution and activity of Fe–Ni catalysts strongly depend on the metals' ratio and their interactions. Key properties affected by the Fe–Ni metal ratio, which played a positive role in co-processing, were a smaller medial metal nanoparticle size (<6 nm), a lower metal–acid site ratio, as well as presence in the catalyst of fcc FeNi alloy structure and fcc Ni doped with Fe. [ABSTRACT FROM AUTHOR]

A crucial role in the miniaturization of electronic and photonic components is played by the integration of ferroelectric thin films on silicon (Si) or silicon nitride (SiN) based platforms. Since the properties of ferroelectric thin films strongly depend on their texture quality and crystallographic orientation, the integration of thin films on these platforms is far from trivial. Consequently, this leads to slow, complex and expensive integration processes. To bridge this gap, a high-throughput method for the integration of highly textured ferroelectric thin films on Si or SiN-based platforms is needed. Therefore, we have investigated a method to facilitate the integration of fiber textured ferroelectric thin films by using an ultrathin (∼7 nm) self out-of-plane oriented La2O2CO3 template film. In this paper, we report a local deposition route of the La2O2CO3 thin film by the scalable inkjet printing method, its inherent out-of-plane crystal orientation, and its lattice match with various ferroelectric thin films. The use of the La2O2CO3 template film as an integration tool for (Pb(Zr,Ti)O3, BaTiO3, and BiFeO3) thin films eventually results in strongly fiber-textured ferroelectric stacks, regardless of substrate type. Consequently, the La2O2CO3 thin film has the potential to serve as a high-throughput integration tool for fiber textured ferroelectric thin films on Si or SiN-based platforms. Moreover, this integration tool could pave the way for large-scale miniaturization of photonic or electronic devices such as phase modulators, resonators, capacitors, etc. [ABSTRACT FROM AUTHOR]

Despite great attention toward transition metal tellurates especially M3TeO6 (M = transition metal) in magnetoelectric applications, control on single phasic morphology-oriented growth of these tellurates at the nanoscale is still missing. Herein, a hydrothermal synthesis is performed to synthesize single-phased nanocrystals of two metal tellurates, i.e., Ni3TeO6 (NTO with average particle size ∼37 nm) and Cu3TeO6 (CTO ∼ 140 nm), using NaOH as an additive. This method favors the synthesis of pure NTO and CTO nanoparticles without the incorporation of Na at pH = 7 in MTO crystal structures such as Na2M2TeO6, as it happens in conventional synthesis approaches such as solid-state reaction and/or coprecipitation. Systematic characterization techniques utilizing in-house and synchrotron-based characterization methods for the morphological, structural, electronic, magnetic, and photoconductivity properties of nanomaterials showed the absence of Na in individual particulate single-phase MTO nanocrystals. Prepared MTO nanocrystals also exhibit slightly higher antiferromagnetic interactions (e.g., TN-NTO = 57 K and TN-CTO = 68 K) compared to previously reported MTO single crystals. Interestingly, NTO and CTO show not only a semiconducting nature but also photoconductivity. The proposed design scheme opens the door to any metal tellurates for controllable synthesis toward different applications. Moreover, the photoconductivity results of MTO nanomaterials prepared serve as a preliminary proof of concept for potential application as photodetectors. [ABSTRACT FROM AUTHOR]

A complex deposition process of high-temperature superconducting (HTS) thin films and coated conductors is usually optimized by concentrating on the crystalline quality of the material, thus getting the best possible critical temperature and self-field properties. However, most of the HTS power applications that are based on coated conductors act at high magnetic fields, and thus an alternative approach focusing on the formation of an optimal network of columnar flux pinning centers is more reasonable. Therefore, we systematically show how a lengthening of the deposition distance produces perfectly aligned and distinctly longer self-assembled BaZrO3 (BZO) nanorods within the YBa2Cu3O6+x (YBCO) matrix. This method unambiguously enhances in-field properties such as pinning force, critical current density, and its isotropy along the YBCO c axis. The experimental results, especially formation of the c peak where the relative length of the nanorod is a key issue, are confirmed by the vortex dynamics simulations. Finally, we present a semiquantitative model governing the formation of nanorods that explains the experimentally observed improved nanorod growth as a function of the deposition distance via the associated variation of the fractional partial pressure between atomic species within the laser plume. [ABSTRACT FROM AUTHOR]

A new study investigates the effect of post-annealing on the distributions and sizes of single Y-Ba-Cu-O particles on SrTiO3 substrates.

Hackmanites, a variety of sodalite with the general formula Na8Al6Si6O24(Cl,S)2, are a family of nature‐based smart materials having the ability for reversible photochromism upon UV or X‐ray exposure. Being nontoxic, cheap, and durable, hackmanite would be an optimal material for the visual detection of the presence of X‐rays in simple portable systems. However, its X‐ray‐induced coloring abilities are so far known only qualitatively. In this work, a combination of experimental and computational methods is used to reveal the mechanism of X‐ray‐induced color changing in these materials. Finally, their use is demonstrated both in color intensity‐based X‐ray dosimetry and photochromic X‐ray imaging. [ABSTRACT FROM AUTHOR]

Isotropic bulk nanocomposite permanent magnets were produced with strontium hexaferrite, SrO·6Fe2O3, and magnetite, Fe3O4, as the magnetically hard and soft components. A novels synthesis scheme based on the partial reduction of SrO·6Fe2O3 was employed. In two parallel experiments, nano- and microcrystalline SrO·6Fe2O3 particles were compacted into pellets along with a controlled, understoichiometric amount of potato starch as a reducing agent. The pellets were then sintered in a passive atmosphere. Based on XRD and room temperature magnetic hysteresis measurements, it was concluded that a fraction of the SrO·6Fe2O3 input material had been reduced into Fe3O4. In comparison with pure SrO·6Fe2O3 control pellets, these composites exhibited maximum energy product increases in excess of 5 % due to remanence boosting. The improvement of magnetic properties was attributed to an efficient exchange spring coupling between the magnetic phases. Interestingly, as the synthesis scheme also worked for microcrystalline SrO·6Fe2O3 , the method could presumably be adapted to yield crystallographically oriented bulk nanocomposite magnets.

Magnetoresistive Sr2FeMoO6 thin films were grown by pulsed laser deposition with three different thicknesses 150 nm, 270 nm and 500 nm. Structural, magnetic and magneto-transport properties of the films were measured. Structural properties showed that impurity phases are formed when the film thickness exceed limiting thickness over 300 nm. Otherwise no major differences were observed in structural and magnetic properties between the films. The semiconductive upturn was observed in all ρ(T) curves, but it was notably smaller for the two thickest films. At 350 K the magnetoresistive (MR) behaviour was very similar for all the films, but at 10 K the negative MR was clearly largest for the thickest film and also the shape of the curve in low fields deviated from others.

Investigating the preparation of two batches of YBCO powder and determine their magnetic properties with a SQUID-magnetometer and microwave absorption measurement is discussed. It is found that adding annealing times strengthens the interparticle weak links and reduces their number, which is observed as a higher critical field of the weak links and less curvature in the field dependency of the magnetization is presented.

Er-doped phosphate glass ceramics were fabricated by melt-quenching technique followed by a heat treatment. The effect of the crystallization on the structural and luminescence properties of phosphate glasses containing Al2O3, TiO2, and ZnO was investigated. The morphological and structural properties of the glass ceramics were characterized by Field Emission-Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), and micro-Raman spectroscopy. Additionally, the luminescence spectra and the lifetime values were measured in order to study the influence of the crystallization on the spectroscopic properties of the glasses. The volume ratio between the crystal and the glassy phases increased along with the duration of the heat treatment. The crystallization of the glass ceramics was confirmed by the presence of sharp peaks in the XRD patterns and different crystal phases were identified depending on the glass composition. Sr(PO3)2 crystals were found to precipitate in all the investigated glasses. As evidenced by the spectroscopic properties, the site of the Er3+ ions was not strongly affected by the heat treatment except for the fully crystallized glass ceramic which does not contain Al2O3, TiO2, and ZnO. An increase of the lifetime was also observed after the heat treatment of this glass. Therefore, we suspect that the Er3+ ions are incorporated in the precipitated crystals only in this glass ceramic [ABSTRACT FROM AUTHOR]

The colossal magnetoresistive insulator to metal switching of almost nine orders of magnitude under the significantly reduced magnetic field is achieved by illumination for the low bandwidth manganite thin films. Similarly, by changing the measuring bias voltage through the sample the required magnetic field for insulator-metal transition can be further fine-tuned. By applying a magnetic field of suitable strength, the samples can also be tuned to be extra sensitive to the illumination having colossal effect on the resistivity at low temperatures. This kind of utilizing of multiple external stimulants, which together change the properties of the material, could have significant impact on the new generation of phase-change memories working under affordable conditions. [ABSTRACT FROM AUTHOR]

Photo-induced magnetization has been studied in small-bandwidth manganite PrCaMnO ( x = 0.1) (PCMO) bulk and thin films. It is observed that the persistent change in magnetization under optical excitation is much stronger in epitaxial thin films of PCMO compared to the bulk. This change is manifested in a change of both coercive field and Curie temperature of the thin films. Stronger photo-induced effect in the thin films might have their origin in the substrate-induced strain effect on the magnetic properties. [ABSTRACT FROM AUTHOR]

The magnetocaloric applicability of the perovskite-structured (Pr,Ca) manganite family (PCMO) was estimated based on the magnetic transition entropies of polycrystalline bulk samples. Transitions in the temperature range from 5 to 400 K were investigated in external fields up to 5 T. Earlier results published on the matter were reproduced, extended to Ca concentrations below $x = 0.2$ and up to $x = 1$ , and complemented by determining standardized refrigerant capacity estimates corresponding to the largest entropy changes detected in each sample. The quantitative agreement between the measured transition entropies and literature also served to verify a time-optimized data collection method based on quick temperature scans of magnetization at constant magnetic fields. Making use of the mathematical regularity of magnetization curves, improved time, and cryogen efficiency was arguably attained compared with a more traditional data collection method without significant loss of accuracy. The results of this paper convey a very graphical overview of the quite well established phase diagram of PCMO and promise a significant magnetocaloric effect below 150 K, possibly on par with that exhibited by Gd-based alloys around room temperature. However, little hope can be offered for the room temperature refrigeration applications of PCMO. [ABSTRACT FROM AUTHOR]

Hall coefficient, electrical conductivity, and electron mobility are investigated for n-ZnSe:Yb single crystals with high concentration of electrically active background impurities (( [ABSTRACT FROM AUTHOR]

The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with N,N'-bis (3,5-di-tert-butyl-2-hydroxy-phenyl)-l,2-phenylenediamine (H4N2O2) are reported. A formally molybdenum(Vl) complex [Mo(N2O2)CI2(dmf)2] (l) was synthesized by the reaction between [MoO2Cl2(dmf)2] and H4N2O2, whereas the other molybdenum(VI) complex [Mo(N2O2)(HN2O2)] (2) was formed when [MoO2(acac)2] was used as a molybdenum source. Both complexes represent a rare case of the MoVIion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations indicate that complex 2 is the first stable molybdenum (VI) amidophenoxide radical. [ABSTRACT FROM AUTHOR]