News

Professor Vid Bobnar, PhD from the Department of Condensed Matter Physics F5, researchers from the Advanced Materials Department K9, and researchers from France, Switzerland, the Netherlands and the Czech Republic have published in Applied Physics Letters the article Large imprint in epitaxial 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 thin films for piezoelectric energy harvesting applications.

Pure and high crystalline quality 500 nm thick PMN–33PT films were grown by pulsed laser deposition on various SrRuO3 buffered substrates. Under compressive epitaxial strain, i.e. under small lattice mismatch between the substrate and PMN–33PT, high teragonality and ferroelectric P-E loops are stabilized. On the other hand, the strain is relaxed in PMN–33PT grown on a substrate with a larger lattice mismatch, and the film displays a relaxor-like hysteresis loop and enhanced piezoelectric response. Both the strained and relaxed SRO/PMN–33PT/Au capacitors exhibit a very large negative self-bias, which is induced by the alignment of defect dipoles with the polarization and is tuned by the epitaxial strain. This imprint permits the stabilization of a robust positive polarization state and low dielectric permittivity. The functional response of our films is in fact comparable to PZT-based thin films with the highest figure of merit, and demonstrates the possibility of developing piezoelectric devices based on high quality PMN–PT thin films.

As part of the University of Ljubljana Week 2022 dr. Matjaž Gomilšek, a member of the Department of Condensed Matter Physics F5 at the Jožef Stefan Institute and the Faculty of Mathematics and Physics at the University of Ljubljana, received the Ceremonial Charter for Young University Teachers and Associates. He was awarded for dedicated and innovative teaching and research work with the citation:

»Asist. dr. Matjaž Gomilšek is a teaching assistant at the Faculty of Mathematics and Physics, University of Ljubljana, where he obtained his PhD in Physics in 2018. In addition to his regular teaching work he is a co-organizer of the Physics in Ljubljana summer school. He is exceptionally successful in scientific research as he has already published 23 papers in recognized international journals and gave several invited lectures abroad. He is a recipient of numerous awards, including the Jožef Stefan Golden Emblem Prize 2020.«

During November 21–24, 2022, the international conference “European C-MetAC Days 2022” took place in Split, Croatia. The conference is organized annually by the European Integrated Center for the Development of New Metallic Alloys and Compounds, a legal successor of the European network of Excellence »Complex Metallic Alloys – CMA« from the 7th EU Framework program. A member of the European C-MetAC is also the Condensed Matter Physics Department of the Jožef Stefan Institute. The conference topics were the development and physical properties of new generations of metallic alloys. The first day of the conference was dedicated to honour scientific achievements of prof. Janez Dolinšek, at the occasion of his 65th birthday anniversary by a workshop “High-Entropy Alloys: From basic studies to industrial applications”. There, the lecturers have presented scientific achievements of Prof. Dolinšek in the fields of quasicrystals, complex metallic alloys and high-entropy alloys and emphasized his long-term cooperation with the members and groups incorporated in the European C-MetAC. After the workshop, the international colleagues and peers have arranged a short celebration entertainment.

Members of the Condensed Matter Physics Department dr. Jože Luzar, assist. prof. Stanislav Vrtnik, dr. Primož Koželj, dr. Andreja Jelen, dr. Magdalena Wencka, Darja Gačnik, Peter Mihor, prof. Janez Dolinšek and the member of the Center of Excellence in Nanoscience and Nanotechnology dr. Bojan Ambrožič, together with the colleagues from the Faculty of Chemistry and Chemical Technology of the Ljubljana University, National Institute of Chemistry and the Slovak University of Technology in Trnava, Slovakia, have discovered the first »supersilent« high-entropy alloys for alternating-current applications. The ferromagnetic high-entropy materials AlCoFeNiCux (x = 2.0–3.0) show a combination of magnetic softness and vanishing magnetostriction and do not vibrate mechanically in an alternating magnetic field. Consequently, they do not emit annoying sound waves, known e.g. as the »humming« noise of an electrical grid transformer. The materials are suitable for the fabrication of supersilent (inaudible to a human ear) transformers, magnetocaloric coolers and other humming electromagnetic machinery based on periodic magnetization and demagnetization of the components. The authors have published the results in a paper Zero-magnetostriction magnetically soft high-entropy alloys in the AlCoFeNiCux (x = 2.0–3.0) system for supersilent applications, which has appeared recently in the journal Advanced Materials Interface.

On 4 October 2022, the Prizes of Dr. Uroš Seljak Prizes for the best scientific publications by students were awarded for the first time at the University of Ljubljana. The prizes were awarded by the honorary patronage of the President of the Republic of Slovenia, Borut Pahor, donor Dr. Uroš Seljak, University of Ljubljana and the American-Slovenian Educational Foundation (ASEF). The Prizes of Dr. Uroš Seljak are intended to encourage and support scientific publications by female and male students in the Bachelor and Masters levels in the Republic of Slovenia, and to promote mentoring of students. Among the recipients of the prize are our young researchers Katja Gosar and Aljaž Kavčič. Katja Gosar received the prize for her scientific publication in the field of quantum devices, and Aljaž Kavčič for his scientific publication in the field of biointegrated photonics. Their mentors, Dr. Peter Jeglič, Head of the Cold Atoms Laboratory, and Dr. Matjaž Humar, Head of the Biointegrated Photonics Laboratory, were awarded a plaquette for mentorship.