Magnetism in a-RuCl3 : Dependence on Coulomb Interaction and Hund's Coupling

Hoshin Gong,Kyoo Kim,Sungdae Ji,김봉재,B. I. Min 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.11

Employing the density functional theory, we have investigated the roles of Coulomb and Hund's interactions in the electronic and magnetic properties of newly discovered ff-RuCl3 having the R3 symmetry, which is in close proximity of the Kitaev system. We show that both the size and the direction of local magnetic moment are highly dependent on Coulomb and Hund's interactions, and the spin and orbital parts show different behaviors. The validity of the so-called jeff picture is accessed upon interaction parameters, and the explicit roles of Hund's interaction in the local electronic structures and magnetic properties are discussed.

Resonant X-ray Scattering Study of Anisotropic Charge Distribution of Gd Ions in GdB4

Sangyun Hwang,Byeong-Gwan Cho,Tae-Young Koo,Sungdae Ji,Beongki Cho,Ki Bong Lee 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.6

Temperature dependence of anisotropic tensor susceptibility (ATS) scattering intensities of GdB4 were measured near L-edges of Gd to investigate how spin ordering affects ATS. ATS scattering intensities for L2- and L3-edges show different temperature dependence below TN. At L3-edge the intensities reflect spin order parameter while intensities at L2-edge do not show noticeable change. The difference is explained in terms of spin-orbit coupling and isotropic distribution of spin-polarized 5d states of Gd ions. Above TN ATS scattering intensities demonstrate that thermal motions enhance charge distribution anisotorpy of Gd 5d states in paramagnetic phase.

Electric Multipole Transitions of Resonant X-ray Scattering for Studying Orbital Specific Magnetization in TmB4

Sangyun Hwang,Changyong Song,Byeong-Gwan Cho,Taeyeong Koo,Sungdae Ji,Beongki Cho,Ki Bong Lee 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.6

Strongly intertwined interaction among spin, orbital and charge degrees of freedom is the essence to induce emergent materials properties, and the investigation to understand their interplay has been actively pursued. In particular, resonant X-ray scattering technique has demonstrated powerful applications in unveiling their long-range ordering behavior with its enhanced sensitivity to the aforementioned degree of freedom. Here, we further demonstrated the spectroscopic application of the technique by providing experimental evidence to reveal spin polarizations in 4f and 5d orbital of the magnetic Tm ions with the orbital-selectivity, which introduced a route to understand fundamental mechanism of spin polarization in the compound. The enhanced sensitivity of the resonant X-ray scattering to various electric multipole transitions expects to find strong applications in studying various spin and polar ordering in materials to include high-order moments.

High-energy Magnetic Excitations in Underdoped La1.90Sr0.10CuO4

Kentaro Sato,Masato Matsuura,Masaki Fujita,Ryoichi Kajimoto,Sungdae Ji,Kazuhiko Ikeuchi,Mitsutaka Nakamura,Yasuhiro Inamura,Masatoshi Arai,Masanori Enoki,Kazuyoshi Yamada 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12

We measured the magnetic excitations in underdoped (UD) La1.90Sr0.10CuO4 by using inelasticneutron scattering over a wide energy range. We succeeded in observing the high-energy excitationsup to '160 meV. Hour-glass-like magnetic excitation, which is commonly seen in the superconductingphase of cuprate oxides, was confirmed. The Ecross (the energy where the dispersion is closestto the ( 12 , 12 ) reciprocal position) of 40 meV follows a linear relation between Ecross and the dopedhole concentration in the UD region. From the dispersion of high-energy excitations above Ecross,we successfully found an effective nearest neighbor interaction (Jeff ) of 102 ± 2 meV. This Jeff issmaller than the nearest neighbor interaction J(=132 meV) in the parent compound La2CuO4,indicating a reduction of Jeff by hole-doping.

Impact of Breed on the Fecal Microbiome of Dogs under the Same Dietary Condition

( Kondreddy Eswar Reddy ),( Hye-ran Kim ),( Jin Young Jeong ),( Kyoung-min So ),( Seul Lee ),( Sang Yun Ji ),( Minji Kim ),( Hyun-jung Lee ),( Sungdae Lee ),( Ki-hyun Kim ),( Minseok Kim ) 한국미생물 · 생명공학회 2019 Journal of microbiology and biotechnology Vol.29 No.12

The gut microbiome influences the health and well-being of dogs. However, little is known about the impact of breed on the fecal microbiome composition in dogs. Therefore, we aimed to investigate the differences in the fecal microbiome in three breeds of dog fed and housed under the same conditions, namely eight Maltese (8.0 ± 0.1 years), eight Miniature Schnauzer (8.0 ± 0.0 years), and nine Poodle dogs (8.0 ± 0.0 years). Fresh fecal samples were collected from the dogs and used to extract metagenomic DNA. The composition of the fecal microbiome was evaluated by 16S rRNA gene amplicon sequencing on the MiSeq platform. A total of 840,501 sequences were obtained from the 25 fecal samples and classified as Firmicutes (32.3-97.3% of the total sequences), Bacteroidetes (0.1-62.6%), Actinobacteria (0.2-14.7%), Fusobacteria (0.0-5.7%), and Proteobacteria (0.0-5.1%). The relative abundance of Firmicutes was significantly lower in the Maltese dog breed than that in the other two breeds, while that of Fusobacteria was significantly higher in the Maltese than in the Miniature Schnauzer breed. At the genus level, the relative abundance of Streptococcus, Fusobacterium, Turicibacter, Succinivibrio, and Anaerobiospirillum differed significantly among the three dog breeds. These genera had no correlation with age, diet, sex, body weight, vaccination history, or parasite protection history. Within a breed, some of these genera had a correlation with at least one blood chemistry value. This study indicates that the composition of the fecal microbiome in dogs is affected by breed.

조사료와 농후사료의 급여 순서가 In vitro 반추위 발효성상, 총 가스 발생량과 메탄 발생량에 미치는 영향

이유경,이성실,성필남,이슬,백열창,김기현,이성대,천주란,지상윤,김정은,Lee, Yookyung,Lee, Sungsill,Seong, Pilnam,Lee, Seul,Baek, Youlchang,Kim, Kihyun,Lee, Sungdae,Chun, Julan,Ji, Sangyun,Kim, Jungeun 한국초지조사료학회 2021 한국초지조사료학회지 Vol.41 No.2

본 연구는 국내 고유종인 한우에서 1) 농후사료 급여 후 조사료 급여, 2) 조사료 급여 후 농후사료 급여, 3) TMR 급여의 총 세 가지 형태의 사료급여가 반추위 발효성상, 총 가스 및 메탄 발생량에 미치는 영향을 in vitro로 평가하기 위해 수행되었다. 사료 급여 형태에 따라 반추위 환경이 변화할 것으로 가설을 세우고, 옥수수 (M)와 티모시 (T)를 기질로 하여 반추위액의 24시간 in vitro 배양을 실시하였다. 따라서 시험 처리구는 총 6개로 구성되었다: M1, M2, M3, T1, T2, T3. 반추위 pH는 사료 급여방식 2에서 다른 처리구보다 높았고 (P < 0.001), 티모시 기질에서 옥수수 기질보다 높았다 (P < 0.001). 휘발성 지방산 (VFA; volatile fatty acid) 조사항목들 (Total VFA, acetate, propionate, butyrate, valerate)은 사료 급여방식 1에서 가장 높았고 급여방식 2에서 가장 낮았으며 (P < 0.001), 옥수수 기질에서 더 많이 생산되었다 (P < 0.001). 반추위액 내 acetate:propionate 비율은 사료 급여방식에 따른 효과는 없었으나 (P = 0.116), 티모시 기질이 옥수수 기질보다 더 높은 값을 나타냈다 (P < 0.001). 암모니아태 질소 (NH₃-N)는 사료 급여방식 1에서 다른 처리구보다 높았으며(P < 0.001), 티모시 기질에서 높은 수치를 보였다 (P < 0.001). 총 가스 및 메탄가스 발생량은 사료 급여방식 1에서 가장 높았고(P < 0.001), 옥수수 기질에서 더 많이 생산되었다 (P < 0.001). 메탄은 이산화탄소의 20배 이상의 지구온난화효과를 갖는 것으로 알려져 있고, 반추가축이 섭취한 에너지의 손실로 작용하고 있어 장내발효 메탄 발생량을 저감하는 것은 매우 중요한 과제라 할 수 있다. 반추가축에서 사료급여 방식에 따른 메탄 발생량 차이에 대한 결론을 얻기 위해서는 보다 다각적인 형태의 연구가 필요할 것으로 사료된다. The objective of this study was to evaluate effects of feeding methods on in vitro ruminal fermentation, total gas and methane production in Hanwoo steers. Six Hanwoo steers fitted with rumen cannula (430 ± 21 kg of body weight) were randomly assigned to one of three feeding systems: 1) feeding forage 1 hour after concentrate, 2) feeding concentrate 1 hour after forage, 3) feeding mixed ration. Rumen fluid sampled from each animals was incubated 24 hours with maize or timothy substrates in in vitro. Ruminal pH was increased in feeding method 2 or maize substrate than that of other methods or timothy substrate (P < 0.001). The production of total volatile fatty acid, acetate, propionate, butyrate, and valerate were increased when steers fed diets using feeding method 1 or rumen fluid was incubated with maize substrate (P < 0.001). Increased production of total gas and methane was observed in feeding method 1 and maize substrate compared to those of other methods or timothy substrate (P < 0.001). Due to the inconsistent results between ruminal fermentation and gas production in this study, further research is required to estimate effects of feeding method on enteric fermentation and gas production in in vivo.

Majorana fermions in the Kitaev quantum spin system α-RuCl₃

Do, Seung-Hwan,Park, Sang-Youn,Yoshitake, Junki,Nasu, Joji,Motome, Yukitoshi,Kwon, Yong ,Seung,Adroja, D. T.,Voneshen, D. J.,Kim, Kyoo,Jang, T.-H.,Park, J.-H.,Choi, Kwang-Yong,Ji, Sungdae Nature Publishing Group 2017 Nature physics Vol.13 No.11

<P>Geometrical constraints to the electronic degrees of freedom within condensed-matter systems often give rise to topological quantum states of matter such as fractional quantum Hall states, topological insulators, and Weyl semimetals(1-3). In magnetism, theoretical studies predict an entangled magnetic quantum state with topological ordering and fractionalized spin excitations, the quantum spin liquid(4). In particular, the so-called Kitaev spin model(5), consisting of a network of spins on a honeycomb lattice, is predicted to host Majorana fermions as its excitations. By means of a combination of specific heat measurements and inelastic neutron scattering experiments, we demonstrate the emergence of Majorana fermions in single crystals of alpha-RuCl3, an experimental realization of the Kitaev spin lattice. The specific heat data unveils a two-stage release of magnetic entropy that is characteristic of localized and itinerant Majorana fermions. The neutron scattering results corroborate this picture by revealing quasielastic excitations at low energies around the Brillouin zone centre and an hour-glass-like magnetic continuum at high energies. Our results confirm the presence of Majorana fermions in the Kitaev quantum spin liquid and provide an opportunity to build a unified conceptual framework for investigating fractionalized excitations in condensed matter(1,6-8).</P>