20.500.12556/RUL-179209 Študija magnetnih lastnosti antiferomagneta $\mathrm{Ba_9 Yb_2 Si_6 O_{24}}$ z elektronsko paramagnetno resonanco Study of magnetic properties of $\mathrm{Ba_9 Yb_2 Si_6 O_{24}}$ with electron paramagnetic resonance Kvantni materiali, v katerih je med magnetnimi ioni prisotna močna frustracija, so potencialni kandidati za realizacijo kvantne spinske tekočine. To je stanje, v katerem se magnetni momenti atomov ne uredijo niti pri temperaturi $T = 0$, zaznamujejo pa ga nenavadne fizikalne lastnosti, kot so močne kvantne fluktuacije, kvantna prepletenost ter frakcijske spinske vzbuditve. Zaradi njihove potencialne uporabe v tehnologiji so kvantne spinske tekočine aktualno področje raziskav v fiziki trdne snovi. V zaključni nalogi je z metodo elektronske paramagnetne resonance analiziran antiferomagnet $\mathrm{Ba_9 Yb_2 Si_6 O_{24}}$, ki je eden od kandidatov za realizacijo takšnega stanja. Rezultati meritev ne kažejo nenadnih sprememb v spektru, ki bi namignile na magnetno ureditev materiala do temperature $T = 4 \mathrm{K}$. Energijski nivoji Yb$^{3+}$ ionov, ki narekujejo magnetne lastnosti tega kvantnega magneta, se v kristalnem polju razcepijo na Kramersove dublete. Iz širin spektra, ki imajo zaradi relaksacij preko Orbachovega procesa eksponentno temperaturno odvisnost, je bil izmerjen tudi energijski razcep med osnovnim in prvim vzbujenim Kramersovim dubletom. Quantum materials in which strong magnetic frustration exists among the magnetic ions are promising candidates for the realization of a quantum spin liquid. This exotic state is characterized by the absence of long-range magnetic order even at temperature $T = 0$, and by unusual physical properties such as strong quantum fluctuations, quantum entanglement, and fractionalized spin excitations. Due to their potential technological applications, quantum spin liquids have become an active and rapidly growing field of research in condensed matter physics. In this thesis, the antiferromagnet $\mathrm{Ba_9 Yb_2 Si_6 O_{24}}$, which is one of the candidates for the realization of such a state, is analyzed using the method of electron paramagnetic resonance. The measurements do not show any abrupt changes in the spectrum that would indicate magnetic ordering of the material down to a temperature of $T = 4 \mathrm{K}$. The energy levels of the Yb$^{3+}$ ions, which determine the magnetic properties of this quantum magnet, split into Kramers doublets in the crystal field. From the linewidths of the spectrum, which exhibit an exponential temperature dependence due to the Orbach process, the energy splitting between the ground and the first excited Kramers doublet was also determined. elektronska paramagnetna resonanca kvantna spinska tekočina magnetizem orbitalna vrtilna količina spin Zeemanova interakcija Orbachov proces izmenjalna interakcija $\mathrm{Ba_9 Yb_2 Si_6 O_{24}}$ electron paramagnetic resonance quantum spin liquid magnetism orbital angular momentum spin Zeeman interaction Orbach process exchange interaction $\mathrm{Ba_9 Yb_2 Si_6 O_{24}}$ true false false Slovenski jezik Angleški jezik Zaključna naloga 2026-02-07 08:15:05 2026-02-07 08:15:11 2026-02-12 04:35:58 0000-00-00 00:00:00 2026 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 159311 267965699 21163.pdf 21163.pdf 1 A507FEE21FB32ACE684947AA1E948ABE c7b45db885080cd55fd679532dc38361bec960575dd1bb6b9de68bf59ac58aff a1518ee0-03f4-11f1-a1ba-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=227501 Fakulteta za matematiko in fiziko 0 0 0