Unusual magnetic and transport properties in HoMn6_6Sn6_6 kagome magnet

With intricate lattice structures, kagome materials are an excellent platform to study various fascinating topological quantum states. In particular, kagome materials, revealing large responses to external stimuli such as pressure or magnetic field, are subject to special investigation. Here, we study the kagome-net HoMn$_6$Sn$_6$ magnet that undergoes paramagnetic to ferrimagnetic transition (below 376 K) and reveals spin-reorientation transition below 200 K. In this compound, we observe the topological Hall effect and substantial contribution of anomalous Hall effect above 100 K. We unveil the pressure effects on magnetic ordering at a low magnetic field from the pressure tunable magnetization measurement. By utilizing high-resolution angle-resolved photoemission spectroscopy, Dirac-like dispersion at the high-symmetry point K is revealed in the vicinity of the Fermi level, which is well supported by the first-principles calculations, suggesting a possible Chern-gapped Dirac cone in this compound. Our investigation will pave the way to understand the magneto-transport and electronic properties of various rare-earth-based kagome magnets

Magnetic and Transport Properties of R3TiSb5 (R=Ce;Pr;Nd) Compounds

Randall S. Filippone, Electrical Engineering TechnologyFaculty Mentor(s): Professor Arjun K. Pathak, Physics Rare-earth (R) intermetallics show a wealth of interesting fundamental physics due to localized 4f electrons. Importantly, the physical behaviors of these compounds can be tailored by controlling either or both chemistry and structure, hence they remain an intriguing subject for materials science and condensed matter physics communities. Here we present magnetic and transport properties of ternary rare-earth transition metal antimonides with the stoichiometry R3TiSb5 (R=Ce, Nd, Pr). The compounds crystallize in the anti-Hf5CuSn3 -type hexagonal structure, space-group P63/mcm (hP18). Our magnetic measurements show that the compounds with R=Ce, Nd undergo antiferromagnetic transition below 5K. However, the compound with R=Pr does not show magnetic ordering down to 1.5K. The resistivity for R=Nd was also measured from 2 to 300K at magnetic field up to 5 Tesla. The resistivity shows metallic behavior with a transition around 5K for R=Nd, which is consistent with the magnetic measurement. This work has been carried out in collaboration between Buffalo State College, the University at Genova, Italy, and Institut Laue-Langevin, Grenoble, France.https://digitalcommons.buffalostate.edu/srcc-sp21-physgeosci/1005/thumbnail.jp

Rapid Solidification for Metal Ribbons

Randall S. Filippone, Electrical Engineering Technology, Liam Hulsebosch, Physics, Jacob Casey, PhysicsFaculty Mentor(s): Professor Arjun Pathak, Physics Rapid solidification is a technique to prepare materials with unique microstructure for desire functionality. This technique involves shooting a stream of molten material onto a spinning copper wheel where it solidifies quickly to form a ribbon of metal. In the typical melt-spinning process, about 5 to 10 g of the alloy is placed inside a quartz or sometimes boron nitride crucible depending on the materials melting temperature, and then the crucible is inserted into the circular induction coil. The current with several amps will apply to the coil, which provides enough heat to the sample, and eventually, it melts. To maximize the melting process, samples temperature should rise several degrees above the melting temperature of the alloy of which ribbons to be prepared. When the temperature reaches the desired point, usually above 100 to 150 degrees C above the melting point, molten metallic liquid eject by Air-pressurization through a fine nozzle of quartz/or boron nitride onto a fast rotating copper wheel, which usually rotates at 3000 rpm (in our equipment). Such high speed offers rapid solidification rates several thousand degrees centigrade per second to freeze the atoms of the liquid phase. We are currently installing melt spinner equipment at the physics department and planning to get ready to synthesize metallic samples in near future. Here we present the installation process of the melt spinner, optimization, and importance of this technique for material science research.https://digitalcommons.buffalostate.edu/srcc-sp21-physgeosci/1003/thumbnail.jp

Alterations of colonic function in the Winnie mouse model of spontaneous chronic colitis

The Winnie mouse, carrying a missense mutation in Muc2, is a model for chronic intestinal inflammation demonstrating symptoms closely resembling inflammatory bowel disease (IBD). Alterations to the immune environment, morphological structure, and innervation of Winnie mouse colon have been identified; however, analyses of intestinal transit and colonic functions have not been conducted. In this study, we investigated in vivo intestinal transit in radiographic studies and in vitro motility of the isolated colon in organ bath experiments. We compared neuromuscular transmission using conventional intracellular recording between distal colon of Winnie and C57BL/6 mice and smooth muscle contractions using force displacement transducers. Chronic inflammation in Winnie mice was confirmed by detection of lipocalin-2 in fecal samples over 4 wk and gross morphological damage to the colon. Colonic transit was faster in Winnie mice. Motility was altered including decreased frequency and increased speed of colonic migrating motor complexes and increased occurrence of short and fragmented contractions. The mechanisms underlying colon dysfunctions in Winnie mice included inhibition of excitatory and fast inhibitory junction potentials, diminished smooth muscle responses to cholinergic and nitrergic stimulation, and increased number of α-smooth muscle actin-immunoreactive cells. We conclude that diminished excitatory responses occur both prejunctionally and postjunctionally and reduced inhibitory purinergic responses are potentially a prejunctional event, while diminished nitrergic inhibitory responses are probably due to a postjunction mechanism in the Winnie mouse colon. Many of these changes are similar to disturbed motor functions in IBD patients indicating that the Winnie mouse is a model highly representative of human IBD. NEW &amp; NOTEWORTHY This is the first study to provide analyses of intestinal transit and whole colon motility in an animal model of spontaneous chronic colitis. We found that cholinergic and purinergic neuromuscular transmission, as well as the smooth muscle cell responses to cholinergic and nitrergic stimulation, is altered in the chronically inflamed Winnie mouse colon. The changes to intestinal transit and colonic function we identified in the Winnie mouse are similar to those seen in inflammatory bowel disease patients. </jats:p

Unusual magnetic and transport properties in HoMn6Sn6 kagome magnet

With intricate lattice structures, kagome materials are an excellent platform to study various fascinating topological quantum states. In particular, kagome materials, revealing large responses to external stimuli such as pressure or magnetic field, are subject to special investigation. Here we study the kagome-net HoMn6Sn6 magnet that undergoes paramagnetic to ferrimagnetic transition (below 376 K) and reveals spin-reorientation transition below 200 K. In this compound, we observe the topological Hall effect and substantial contribution of anomalous Hall effect above 100 K. We unveil the pressure effects on magnetic ordering at a low magnetic field from the pressure tunable magnetization measurement. By utilizing high-resolution angle-resolved photoemission spectroscopy, Dirac-like dispersion at the high-symmetry point K is revealed in the vicinity of the Fermi level, which is well supported by the first-principles calculations. Our investigation will pave the way to understanding the magnetotransport and electronic properties of various rare-earth-based kagome magnets.This article is published as Kabir, Firoza, Randall Filippone, Gyanendra Dhakal, Y. Lee, Narayan Poudel, Jacob Casey, Anup Pradhan Sakhya et al. "Unusual magnetic and transport properties in HoMn 6 Sn 6 kagome magnet." Physical Review Materials 6, no. 6 (2022): 064404. DOI: 10.1103/PhysRevMaterials.6.064404. Copyright 2022 American Physical Society. Posted with permission. DOE Contract Number(s): AC02-07CH11358; AC07-05ID14517; FA9550-17-1-0415; FA9550-20-1-0322