arXiv subjects

Teemu Hynninen

Publications and source records attributed to Teemu Hynninen.

4 recordsLinked to original sources

arXiv2022

Ongoing effects of pandemic-imposed learning disruption on student attitudes

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' expert-like views. Similarly, the students who experienced the remote learning period in high school displayed a lower level of expert-like 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.

physics.ed-ph↗

arXiv2019

First-principles investigations of the magnetic phase diagram of Gd$_{1-x}$Ca$_{x}$MnO$_{3}$

We studied for the first time the magnetic phase diagram of the rare-earth manganites series Gd$_{1-x}$Ca$_{x}$MnO$_{3}$ (GCMO) over the full concentration range based on density functional theory. GCMO has been shown to form solid solutions. We take into account this disordered character by adapting special quasi random structures at different concentration steps. The magnetic phase diagram is mainly described by means of the magnetic exchange interactions between the Mn sites and Monte Carlo simulations were performed to estimate the corresponding transition temperatures. They agree very well with recent experiments. The hole doped region $x<0.5$ shows a strong ferromagnetic ground state, which competes with A-type antiferromagnetism at higher Ca concentrations $x>0.6$.

cond-mat.mtrl-sci↗

arXiv2008

Adsorption of metal impurities on H-terminated Si surfaces and their influence on the wet chemical etching of Si

We use first-principles methods to investigate the adsorption of Cu, Pb, Ag, and Mg onto a H-terminated Si surface. We show that Cu and Pb can adsorb strongly while Ag and Mg are fairly inert. In addition, two types of adsorption states are seen to exist for Pb. We also study the clustering energetics of Cu and Pb on the surface and find that while Cu clusters eagerly, Pb may prefer to form only small clusters of a few atoms. This kind of behavior of impurities is incorporated in kinetic Monte Carlo simulations of wet etching of Si. The simulation results agree with experiments supporting the idea that micromasking by Cu clusters and Pb atoms is the mechanism through which these impurities affect the etching process.

cond-mat.mtrl-sci↗

arXiv2006

High Curie temperatures in (Ga,Mn)N from Mn clustering

The effect of microscopic Mn cluster distribution on the Curie temperature (Tc) is studied using density-functional calculations. We find that the calculated Tc depends crucially on the microscopic cluster distribution, which can explain the abnormally large variations in experimental Tc values from a few K to well above room temperature. The partially dimerized Mn_2-Mn_1 distribution is found to give the highest Tc > 500 K, and in general, the presence of the Mn_2 dimer has a tendency to enhance Tc. The lowest Tc values close to zero are obtained for the Mn_4-Mn_1 and Mn_4-Mn_3 distributions.

cond-mat.mtrl-sci↗