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- ItemSyntheses, crystal structure and magnetic properties of Tl9RETe6 (RE = Ce, Sm, Gd)(Basel : MDPI AG, 2020) Isaeva, A.; Schönemann, R.; Doert, T.The three compounds Tl9RETe6 with RE = Ce, Sm, Gd were synthesized from the elements at 1020 K. Their isostructural crystal structures are ordered derivatives of the Tl5Te3 type with rare-earth metal and thallium occupying different Wyckoff positions. The structures can be understood as charge-ordered in accordance with the Zintl-Klemm concept: 9 Tl+ + RE3+ + 6 Te2-. DFT calculations for Tl9GdTe6, however, result in a low, but finite density of states at the Fermi level. Magnetic data confirm trivalent Gd, but indicate a small amount of Ce4+ in Tl9CeTe6; no indications for long-range magnetic order was found down to T = 2 K.
- ItemImpact of Mn-Pn intermixing on magnetic properties of an intrinsic magnetic topological insulator: the µSR perspective(Bristol : IOP Publ., 2023) Sahoo, M.; Salman, Z.; Allodi, G.; Isaeva, A.; Folkers, L.; Wolter, A.U.B.; Büchner, B.; De Renzi, R.We investigated the magnetic properties of polycrystalline samples of the intrinsic magnetic topological insulators MnPn2Te4, with pnictogen Pn = Sb, Bi, by bulk magnetization and μSR. DC susceptibility detects the onset of magnetic ordering at TN = 27 K and 24 K and a field dependence of the macroscopic magnetization compatible with ferri- (or ferro-) and atiferro- magnetic ordering, respectively. Weak transverse field (wTF) Muon Spin Rotation (μSR) confirms the homogeneous bulk nature of magnetic ordering at the same two distinct transition temperatures. Zero Field (ZF) μSR shows that the Sb based material displays a broader distribution of internal field at the muon, in accordance with a larger deviation from the stoichiomectric composition and a higher degree of positional disorder (Mn at the Pn(6c) site), which however does not affect significantly the sharpness of the thermodynamic transition, as detected by the muon magnetic volume fraction and the observability of a critical divergence in the longitudinal and transverse muon relaxation rates.
- ItemDiscovery, Crystal Growth, and Characterization of Garnet Eu2PbSb2Zn3O12(Weinheim : Wiley-VCH, 2020) Morrow, Ryan; Sturza, Mihai I.; Ray, Rajyavardhan; Himcinschi, Cameliu; Kern, Jonas; Schlender, Philipp; Richter, Manuel; Wurmehl, Sabine; Büchner, BerndSingle crystal specimens of previously unknown garnet Eu2PbSb2Zn3O12 were grown in a reactive PbO:PbF2 flux medium. The crystals were characterized by a combination of X-ray crystallography, magnetization measurements, and the optical techniques of Raman, photoluminescence, and UV/Vis spectroscopy. The material exhibits Van Vleck paramagnetism associated with the J = 0 state of Eu3+, which was possible to accurately fit to a theoretical model. Band structure calculations were performed and compared to the experimental band gap of 1.98 eV. The crystals demonstrate photoluminescence associated with the 4f 6 configuration of the Eu3+ ions sitting at the distorted 8-coordinate garnet A site. The title compound represents a unique quinary contribution to a relatively unexplored area of rare earth bearing garnet crystal chemistry. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemReversible magnetism switching of iron oxide nanoparticle dispersions by controlled agglomeration(Cambridge : Royal Society of Chemistry, 2021) Müssig, Stephan; Kuttich, Björn; Fidler, Florian; Haddad, Daniel; Wintzheimer, Susanne; Kraus, Tobias; Mandel, KarlThe controlled agglomeration of superparamagnetic iron oxide nanoparticles (SPIONs) was used to rapidly switch their magnetic properties. Small-angle X-ray scattering (SAXS) and dynamic light scattering showed that tailored iron oxide nanoparticles with phase-changing organic ligand shells agglomerate at temperatures between 5 °C and 20 °C. We observed the concurrent change in magnetic properties using magnetic particle spectroscopy (MPS) with a temporal resolution on the order of seconds and found reversible switching of magnetic properties of SPIONs by changing their agglomeration state. The non-linear correlation between magnetization amplitude from MPS and agglomeration degree from SAXS data indicated that the agglomerates' size distribution affected magnetic properties.
- ItemTailoring biocompatible Ti-Zr-Nb-Hf-Si metallic glasses based on high-entropy alloys design approach(Amsterdam : Elsevier, 2020) Calin, Mariana; Vishnu, Jithin; Thirathipviwat, Pramote; Popa, Monica-Mihaela; Krautz, Maria; Manivasagam, Geetha; Gebert, AnnettPresent work unveils novel magnetic resonance imaging (MRI) compatible glassy Ti-Zr-Nb-Hf-Si alloys designed based on a high entropy alloys approach, by exploring the central region of multi-component alloy phase space. Phase analysis has revealed the amorphous structure of developed alloys, with a higher thermal stability than the conventional metallic glasses. The alloys exhibit excellent corrosion properties in simulated body fluid. Most importantly, the weak paramagnetic nature (ultralow magnetic susceptibility) and superior radiopacity (high X-ray attenuation coefficients) offer compatibility with medical diagnostic imaging systems thereby opening unexplored realms for biomedical applications.
- ItemMagnetocaloric performance of the three-component Ho1-xErxNi2 (x = 0.25, 0.5, 0.75) Laves phases as composite refrigerants([London] : Macmillan Publishers Limited, part of Springer Nature, 2022) Ćwik, Jacek; Koshkid’ko, Yurii; Nenkov, Konstantin; Tereshina-Chitrova, Evgenia; Małecka, Małgorzata; Weise, Bruno; Kowalska; KarolinaTo date, significant efforts have been put into searching for materials with advanced magnetocaloric properties which show promise as refrigerants and permit realization of efficient cooling. The present study, by an example of Ho1−xErxNi2, develops the concept of magnetocaloric efficiency in the rare-earth Laves-phase compounds. Based on the magneto-thermodynamic properties, their potentiality as components of magnetocaloric composites is illustrated. The determined regularities in the behaviour of the heat capacity, magnetic entropy change, and adiabatic temperature change of the system substantiate reaching high magnetocaloric potentials in a desired temperature range. For the Ho1−xErxNi2 solid solutions, we simulate optimal molar ratios and construct the composites used in magnetic refrigerators performing an Ericsson cycle at low temperatures. The tailored magnetocaloric characteristics are designed and efficient procedures for their manufacturing are developed. Our calculations based on the real empirical data are very promising and open avenue to further experimental studies. Systems showing large magnetocaloric effect (MCE) at low temperatures are of importance due to their potential utilization in refrigeration for gas liquefaction.