Two-channel anomalous Hall effect in SrRuO3

The Hall effect in SrRuO$_3$ thin-films near the thickness limit for ferromagnetism shows an extra peak in addition to the ordinary and anomalous Hall effects. This extra peak has been attributed to a topological Hall effect due to two-dimensional skyrmions in the film around the coercive field; however, the sign of the anomalous Hall effect in SrRuO$_3$ can change as a function of saturation magnetization. Here we report Hall peaks in SrRuO$_3$ in which volumetric magnetometry measurements and magnetic force microscopy indicate that the peaks result from the superposition of two anomalous Hall channels with opposite sign. These channels likely form due to thickness variations in SrRuO$_3$, creating two spatially separated magnetic regions with different saturation magnetizations and coercive fields. The results are central to the development of strongly correlated materials for spintronics.This work is supported by the EPSRC through the Core-to-Core International Network “Oxide Superspin” (EP/P026311/1) and the Doctoral Training Partnership Grant (EP/N509620/1). Additional support from the Office of Basic Energy Sciences Division of Materials Sciences and Engineering, US Department of Energy under Award numbers de-sc0018153, and the Research Center Program of IBS (Institute for Basic Science) in Korea (IBS-R009-D1)

Honeycomb oxide heterostructure: a new platform for Kitaev quantum spin liquid

Kitaev quantum spin liquid, massively quantum entangled states, is so scarce in nature that searching for new candidate systems remains a great challenge. Honeycomb heterostructure could be a promising route to realize and utilize such an exotic quantum phase by providing additional controllability of Hamiltonian and device compatibility, respectively. Here, we provide epitaxial honeycomb oxide thin film Na3Co2SbO6, a candidate of Kitaev quantum spin liquid proposed recently. We found a spin glass and antiferromagnetic ground states depending on Na stoichiometry, signifying not only the importance of Na vacancy control but also strong frustration in Na3Co2SbO6. Despite its classical ground state, the field-dependent magnetic susceptibility shows remarkable scaling collapse with a single critical exponent, which can be interpreted as evidence of quantum criticality. Its electronic ground state and derived spin Hamiltonian from spectroscopies are consistent with the predicted Kitaev model. Our work provides a unique route to the realization and utilization of Kitaev quantum spin liquid

Barrier protection via Toll-like receptor 2 signaling in porcine intestinal epithelial cells damaged by deoxynivalnol

Additional file 2. IPEC-J2 cells pretreated with TLR2 ligand maintained the expression of MCP-1, GM-CSF and TLR2 against DON exposure. IPEC-J2 cells pretreated with or without TLR2 ligand for 24 h were exposed to DON. (A) The bar graph showed the mRNA levels of porcine mcp-1, gm-csf measured using real time-PCR at 1 and 6 h after DON exposure (n = 3). (B) The mRNA levels of porcine tlr2 were measured using real-time quantitative PCR analysis at 6 h. NT represents no treatment. Expression of each mRNA was presented relative to the expression of housekeeping gene, gapdh (n = 3). *P < 0.05; **P < 0.01; ***P < 0.001, determined by one-way ANOVA with Tukey’s posttest

Tuning orbital-selective phase transitions in a two-dimensional Hund's correlated system

Hund's rule coupling ($\textit{J}$) has attracted much attention recently for its role in the description of the novel quantum phases of multi orbital materials. Depending on the orbital occupancy, $\textit{J}$ can lead to various intriguing phases. However, experimental confirmation of the orbital occupancy dependency has been difficult as controlling the orbital degrees of freedom normally accompanies chemical inhomogeneities. Here, we demonstrate a method to investigate the role of orbital occupancy in $\textit{J}$ related phenomena without inducing inhomogeneities. By growing SrRuO$_3$ monolayers on various substrates with symmetry-preserving interlayers, we gradually tune the crystal field splitting and thus the orbital degeneracy of the Ru \textit{t_2_g$}$ orbitals. It effectively varies the orbital occupancies of two-dimensional (2D) ruthenates. Via in-situ angle-resolved photoemission spectroscopy, we observe a progressive metal-insulator transition (MIT). It is found that the MIT occurs with orbital differentiation: concurrent opening of a band insulating gap in the $\textit{d$_x_y} band and a Mott gap in the \textit{d_x$$_z$$_/$$_y$$_z} bands. Our study provides an effective experimental method for investigation of orbital-selective phenomena in multi-orbital materials

Original Article

99 cases were operated while we could not use antibiotics. The author traced X-ray photos on paper and measured areas of the peeled cavities with a planimeter. Results were as follows. 1) 66 cases had increasing stage and the rates were more than 30 %. 2) Cases with good developments showed larger original areas (50〜100cm^2) and smaller increasing rates (less than 30 %). 3) Also their X-ray photos showed coinciding or almost coinciding lines of the apices of lungs and the bases of cavities, but we had to take precautions against suppuration when they showed a horizontal line several days after operation. 4) Most of too high degree of adhesion or thickning of pleura did not show good results. When we found a cord which we must manage with some procedures by pneumolysis we must attend to suppuration too. 5)We ought to resect 4th or 5th rib more than 20 cm and 5th or 4th several cm supplementary. 6) As a method of constriction we commend the INVAGI.NATION method. 7) The author noticed in a considerable number of cases that the areas of cavities increased again after they kept long balanced stages

Atherosclerosis V, Proceeding of the Fifth International Symposium, A.M. Gotto, L.C. Smith, B. Allen, Spring Verlag, 1979(BOOK REVIEW)

Antiviral effect of micafungin on three strains of human rhinoviruses. H1HeLa cells were infected with human rhinovirus type 14 (A), 21 (B), or 71 (C) (100 CCID50) and immediately treated with indicated concentrations of micafungin. Three days after compound treatment antiviral activity was determined by the reduction of cytopathic effect using MTT assay. Cell viability of DMSO-treated cells was set to 0 % and that of uninfected cells was set to 100 %. (TIF 100 kb

페로브스카이트 초박막 루테늄에서의 전자 구조에 대한 계면 제어

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 물리·천문학부(물리학전공), 2022. 8. 노태원.Quantum materials host a variety of phenomena beyond the single-electron band theory. As strongly correlated systems, transition metal oxides (TMOs) exhibit exotic features including ferromagnetism, and unconventional superconductivity. Among TMOs, 4d ruthenates have been extensively studies due to their fine balance between electronic correlations. In such systems, the energy scales of on-site Coulomb interaction (U), Hund’s rule coupling (J), and spin-orbital coupling are comparable, giving rise to a variety of functionalities. In this dissertation, we control the electronic structures of perovskite ruthentates ultrathin films by interfacial engineering. First, we investigate the orbital-selective phases in SrRuO3 (SRO) monolayers via epitaxial strain engineering. Despite vast previous theoretical studies on Hund-driven physics, experimental confirmation has been rare due to experimental difficulties. Here, we demonstrate an experimental method to systematically investigate physics in Hund’s systems. The epitaxial strains modulate tetragonal crystal field, which effectively vary the orbital occupancies. Following the ambient nature of J, we observe a drastic change in electronic sturctures; a metal-insulator transition with an orbital differentiation confirmed by in-situ angle-resolved photoemission spectroscopy. We provide a practical direction for exploring multi-orbital physics as well as device applications in Hund’s systems. Second, we discuss the ferromagnetic properties of ultrathin SRO with oxygen vacancy (VO). In TMOs, control of VO can give rise to many intriguing physical properties. However, inducing VO in SRO has been challenging due to volatility of Ru. Here, we utilize interfacial engineering for VO migration. By changing the growth pressure during the SrTiO3 (STO) capping layer deposition, the kinetic energy of ions arriving to the bottom SRO layer can be controlled. The high kinetic process of pulsed laser deposition (PLD) can overcome the migration energy barrier at STO/SRO and VO can be migrated into SRO. We observe VO in SRO and structural modification in SRO such as c-lattice expansion near the interface. Following, a continuous control of ferromagnetic coercive field of ultrathin SRO is achieved by controlling the amount of VO migration. We conclude that the large amount of VO induces enhancement of perpendicular magnetic anisotropy, resulting in increasing coercive field. Lastly, we investigate multiple anomalous Hall effect (AHE) interpretation in ultrathin SRO films by inducing different magnetic phases. We control the growth pressure during the LaAlO3 capping layer growth for control of the kinetic process during PLD. According to the growth pressure, two different magnetic phases in ultrathin SRO films are induced, and the composition between them can be systematically controlled. We find that the amplitude and sign of AHE change according to the composition of the magnetic phases. Our results indicate that the Berry curvature-driven AHE in ultrathin SRO films is strongly related to its magnetic properties.강상관계 물질은 비페르미 액체성, 초전도와 같은 독특한 현상을 가진다. 단일 전자 밴드 이론으로는 설명할 수 없는 이러한 현상들을 이해하기 위해 전자 간의 관계에 대해 활발하게 조사되어 왔다. 전이 금속 산화물은 강한 상관관계가 있는 시스템 중 하나이며 금속-절연체 전이, 강자성 및 초전도성과 같은 흥미로운 특성을 보인다. 이 중 4d 루테늄은 전자의 상관관계를 연구하기에 적합한 시스템이다. 이 시스템에서는 쿨롱 상호작용 (U), 전자 hopping (t), 그리고 훈트 법칙 커플링 (J) 의 에너지 규모가 비슷할 수 있다. 본 학위 논문에서는 페로브스카이트 초박막 루테늄 산화물의 전자 구조를 박막의 계면 제어를 통해 조사하였다. 첫번째로, 우리는 에피택셜 응력 (epitaxial strain) 제어를 통해 SrRuO3 (SRO) 하나의 층에서 훈트 법칙이 이끄는 모트 전이를 보여준다. 훈트 법칙이 이끄는 상관관계에 대한 이전의 많은 이론 연구에도 불구하고, J 값 또는 오비탈 간의 전자 분포를 실험적으로 조절하기 어려워서 실험적 확인이 거의 없었다. 여기서 우리는 J 와 결정장 (crystal field) 의 경쟁 효과를 활용하였다. 에피택셜 응력 제어는 오비탈 간의 전자 분포를 효과적으로 조절하였다. 그리고, 각도분해 광전자 분광법을 사용하여 모트 전이를 관찰하였다. 우리는 다중 오비탈 시스템에서 훈트 기반 물리를 조사하는 효과적인 방법을 제시하였다.   두번째로, 산소 결손 (oxygen vacancy) 이 있는 초박막 SRO 의 강자성 특성에 대해 논의한다. 전이 금속 산화물에서 산소 결손의 제어는 흥미로운 물리적 특성을 일으킬 수 있다. 하지만 SRO 에 산소결손을 유도하는 것은 루테늄의 높은 휘발성으로 인해 어려웠다. 여기에서 우리는 산소 결손 이동을 위해 계면 제어를 활용하였다. SrTiO3 (STO) 덮음층 증착 동안 성장 압력을 변경함으로써 밑에 SRO 층에 도달하는 이온의 운동 에너지를 제어할 수 있었다. 펄스 레이저 증착 (pulsed laser deposition) 과정 중 높은 운동 에너지는 STO/SRO 계면에서 산소결손 이동 에너지 장벽을 극복할 수 있도록 도와주었다. 우리는 SRO 의 산소결손과 그에 따른 격자 변이를 관찰하였다. 그리고 초박막 SRO 의 보자력 (coercive field) 의 지속적인 제어를 산소결손 이동량을 제어하여 달성하였다. 또한 우리는 많은 양의 산소 결손이 수직 자기 이방성을 높이는 것을 확인하였다. 마지막으로, 우리는 서로 다른 자기 상 (phase) 을 유도하여 초박막 SRO 에서 다중 비정상 홀 효과를 조사하였다. LaAlO3 덮음층 성장 동안 압력을 제어하여 운동에너지를 조절하였다. 성장 압력에 따라 SRO 필름에서 두 개의 서로 다른 자기 상이 유도되었고, 이들 사이의 비율은 체계적으로 제어할 수 있었다. 우리는 비정상 홀 효과의 크기와 부호가 자기 상의 구성에 따라 변한다는 것을 발견하였다. 이 결과는 초박막 SRO 필름의 비정상 홀 효과가 자기 특성과 밀접한 관련이 있음을 나타낸다.Contents List of Figures Abstract Chapter 1. Introduction Chapter 2. Experimental Methods Chapter 3. Orbital-selective phase transition in a two-dimensional correlated system Chapter 4. Hetero-interfacial control for oxygen vacancy migration Chapter 5. Hetero-interfacial control for two-channel anomalous Hall effect Chapter 6. Summary and Outlook List of Publication 국문 초록 (Korean Abstract)박

In-operando spectroscopic ellipsometry studies of IrO2 dynamic instabilities: Guide to in-situ growth of pyrochlore iridate thin films

The instability of iridium oxide at high temperature has long been a bottleneck for in growing pyrochlore iridate thin films in a vacuum chamber. To overcome this problem, we investigated the chemical instability of IrO2 thin films, which are the simplest form of iridate, via in-operando spectroscopic ellipsometry (SE). We observed that IrO2 thin films undergo IrO2 dissociation and IrO3 gas formation depending on the thermodynamic conditions. The chemical kinetics observations of IrO2 were confirmed by ex-situ X-ray diffraction and atomic force microscopy. SE experimental data were compared with models used to describe the evolution of the two chemical reactions. Real-time in-operando SE analysis based on the Maxwell Garnett theory yielded a precise IrO2 dissociation speed for the given thermodynamic conditions. Moreover, the real-time in-operando SE technique allowed us to observe the phase transition from solid IrO2 to gaseous IrO3. This study on the chemical instability of IrO2 at high temperature affords insights into a new method for in-situ pyrochlore iridate and other iridates thin-film growth. © 2019 Korean Physical Society. Published by Elsevier B.V. All rights reserved

Controllable Thickness Inhomogeneity and Berry Curvature Engineering of Anomalous Hall Effect in SrRuO3 Ultrathin Films

In quantum matters hosting electron−electron correlation and spin−orbit coupling, spatial inhomogeneities, arising from competing ground states, can be essential for understanding exotic topological properties. A prominent example is Hall anomalies observed in SrRuO 3 films, which were interpreted in terms of either magnetic skyrmion-induced topological Hall effect or inhomogeneous anomalous Hall effect (AHE). To clarify this ambiguity, we systematically investigated the evolution of AHE with controllable inhomogeneities in SrRuO 3 film thickness (t SRO ). By exploiting the step-flow growth of SrRuO 3 films, we induced a microscopically ordered stripe pattern with one-unit-cell differences in t SRO . The associated spatial distribution of momentum-space Berry curvatures enables a two-channel AHE with hump-like Hall anomalies, which can be continuously engineered according to non-integer t SRO . We further microscopically characterized the stripe-like ferromagnetic domains and two-step magnetic switching behavior in the inhomogeneous SrRuO 3 film. These unique features can be utilized to identify the two-channel AHE model and understand its microscopic origin. © 2020 American Chemical Society11Nsciescopu