The Disputation will be live streamed for everyone else.
The livestream will be activated 15 minutes before the Defense starts.
Trial lecture
February 27, 10:15 AM, Auditorium 2, Chemistry building
Trial lecture title:
“Magnetic exchange interactions: origin and types including direct exchange, super exchange, super-super exchange and RKKY”
The trial lecture will be live streamed for everyone else.
The livestream will be activated 15 minutes before the trial lecture starts.
Kreeringssammendrag/Conferral summary
Forskning på magnetisk kjøling som et alternativ til tradisjonelle kjølemetoder møter utfordringer når det gjelder masseproduksjon av nåværende magnetokaloriske materialer. Denne studien fokuserer på å finjustere de magnetiske egenskapene til høyentropilegeringer og MnNiSi-baserte forbindelser, med mål om å forbedre deres egnethet for effektiv magnetisk kjøling.
Main research findings
Magnetic refrigeration is being explored as a promising alternative to current cooling methods, but existing magnetocaloric materials face challenges for mass production. This thesis investigates two types of materials: high entropy alloys (HEAs) and MnNiSi-based compounds. By changing their compositions, it is possible to tailor their magnetic properties for efficient room temperature refrigeration. By a combination of microscopy techniques, powder diffraction (X-rays and neutrons), caloric and magnetic measurements, a thorough evaluation of the compounds and the magnetic transitions was performed.
The studied V1-xFeCoNiAl1+x and V1-xFeCoNiCu1+x HEAs were ferromagnetic, but had less effective magnetocaloric properties compared to other materials. In contrast, MnNiSi-based compounds exhibited abrupt magnetic transitions due to a structural change. Compositions such as Mn1-xNi1-xFe2xSi0.95Al0.05 with x between 0.31 and 0.32 showed better magnetocaloric performance than the HEAs. Despite internal disorder affecting their magnetocaloric effect in HEAs and MnNiSi compounds, post-synthesis processing was found to improve the MnNiSi-based materials even more, offering a pathway towards competitive MnNiSi-based magnetocaloric materials using abundant elements (Mn, Ni, Si, Fe, and Al).
Candidate contact information
LinkedIn: https://www.linkedin.com/in/bruno-eggert/
Email: bruno.eggert@ife.no
Tel. +47 407 23 949