Search

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.

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

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 accommodation field, B*, is generally defined to be the field at which the cross over from single vortex pinning to collective pinning occurs. It is determined from magnetization curves as the point where the Jc plateau ends and it used as a convenient way of comparing the pinning properties of superconducting films. Similarly, the characteristic field, Bc, can be obtained from magneto-optical (MO) images from when the flux fronts meet in the middle of the film. The matching field, Bc at which there is one vortex line per pinning site, is sometimes thought to be the same as B*, but in BaZrO3-doped YBa2Cu3O7 films the calculated BΦ, is much higher than the observed B*. BΦ, can be determined from angular dependent transport measurements. All of the field values correspond to some special case in the flux pinning in the film and relate to Jc. In this work we have determined Bc, B * and BΦ, for different kinds of YBCO films using MO, magnetization and transport measurements to reveal the deeper meaning of the special fields. [ABSTRACT FROM AUTHOR]