SEMINARIUM
Oddziału Fizyki Magnetyków i Zjawisk Kooperatywnych

Dnia: 04.06.2021 roku (piątek)
o godzinie 10:00 w trybie zdalnym

referat pt.:

Polar bonds assisting ferromagnetism in Uranium hydrides

wygłosi

Dr Ladislav Havela

Department of Condensed Matter Physics, Charles University, Czech Republic

Abstract

5f magnetism in U-based systems is typically a band magnetism, appearing if the U-U distances exceed approx. 340 pm. The 5f band becomes sufficiently narrow to allow the formation of 5f moments. Uranium hydrides are bit out of systematics, they are ferromagnets with high ordering temperatures of 160 K, despite short U-U distances. It decreases in one form, α-UH3, to 331 pm. We have developed a way how to tune the composition by alloying U by diverse transition metals, which can increase T_C over 200 K. Consistently strong ferromagnetism was observed also in UH₂, prepared as metastable in the form of this films. All the experimental evidence of bulk properties and spectroscopies as well as ab initio calculations evidences the importance of polar bonds between U and H, yielding a strong hybridization of U-6d states with H-1s states. It weakens the 5f-6d hybridization ubiquitous in U metal and intermetallic systems, which normally washes out the U moments. Such synthesis of physics and chemistry views helps to identify other cases of U compounds, which can bring the 5f ferromagnetism to ambient conditions.

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