Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session L44: Novel Correlated Electron Magnetism |
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Sponsoring Units: DCMP Chair: Ryan Baumbach, Natl High Magnetic Field Lab Room: LACC 504 |
Wednesday, March 7, 2018 11:15AM - 11:27AM |
L44.00001: Near Ferromagnetism in MnP-Type CoAs Daniel Campbell, Limin Wang, Chris Eckberg, David Graf, Halyna Hodovanets, Johnpierre Paglione We report the low temperature electrical and magnetic properties of single crystal CoAs. This material is isostructural with compounds like MnP, CrAs, and FeAs, which show intriguing superconducting and magnetic states as a function of temperature, magnetic field, and applied pressure. While there is no experimental evidence for magnetic ordering in CoAs, we have performed density functional theory calculations that favor a ferromagnetic ground state. Additionally, heat capacity and magnetization measurements suggest a ferromagnetic instability at low temperatures. De Haas-van Alphen oscillations observed at high fields support the calculated paramagnetic Fermi surface and give a measure of correlation strength. This talk will review the properties of CoAs in the light of other similar transition metal-pnictide binary materials. |
Wednesday, March 7, 2018 11:27AM - 11:39AM |
L44.00002: Magnetic Ordering at Anomalously High Temperatures in Nd and Dy at Extreme Pressures: What about Pr and Yb? Jing Song, Wenli Bi, Daniel Haskel, James Schilling Under sufficiently high pressure one anticipates that the 4f state of a given lanthanide becomes unstable, leading to highly correlated electron effects and exotic physics. Recent four-point resistivity measurements on Nd metal to 2 Mbar pressure reveal that its magnetic ordering temperature To soars to anomalously high values, in analogy with earlier results on the lanthanide Dy. In addition, giant superconducting pair-breaking and resistivity minima are observed in the dilute magnetic alloy Y(Nd) revealing the presence of exotic Kondo effect phenomena that may be responsible for the anomalously high values of To in Nd metal. |
Wednesday, March 7, 2018 11:39AM - 11:51AM |
L44.00003: Nano-manipulation of photo-induced ferromagnetism in an epitaxial manganite Alexander McLeod, Jingdi Zhang, Gufeng Zhang, Kirk Post, Wenbin Wu, Richard Averitt, Dimitri Basov The ground state properties of correlated electron systems can be extraordinarily sensitive to external stimuli, such as temperature, strain, and electromagnetic fields. Such pliancy offers abundant platforms for functionally reconfigurable materials. In this work we present a metastable and reversible photo-induced insulator-metal transition in strained films of the doped manganite La2/3Ca1/3MnO3. Using a novel combination of cryogenic scanning near-field optical microscopy, magnetic force microscopy, and ultrafast laser excitation, we demonstrate both “writing” and “erasing” of a metastable ferromagnetic metal phase with nano-scale finesse. By tracking optical conductivity and magnetism at the nano-scale, we demonstrate cooperativity and stability of the photo-induced over a wide range of temperatures. Comparison of our observations with first-principles electronic structure calculations reveals the key role of lattice strain, which can stabilize nearly degenerate charge-ordered insulator and ferromagnetic metal ground states by way of epitaxial engineering. Informed by these findings, we propose a simple Landau theory capturing the rich interplay of strain, charge order, and magnetism to guide ongoing functional engineering of epitaxial manganites and related materials. |
Wednesday, March 7, 2018 11:51AM - 12:03PM |
L44.00004: Cascade of Metamagnetic Transitions in Heavy Fermion CePtPb Alex Fang, Jeff Sonier, Eundeok Mun, Sarah Dunsiger, Kolawole Akintola, Anand Pal CePtPb crystallizes into a hexagonal ZrNiAl-type structure, where the magnetic Ce-ions form a quasi-Kagome lattice. Other heavy-fermion compounds with this structure, such as CePdAl and YbAgGe, have been shown to have a complicated H-T phase diagram with multiple magnetic phases. Both CePdAl and YbAgGe show a region of strange-metallic behavior near the quantum critical point. In this talk, I will present magnetic-field dependent measurements of resistivity, heat capacity and muon spin relaxation that lead to the construction of a magnetic-field-temperature phase diagram for this compound. The constructed phase diagram and physical properties of CePtPb will be compared to CePdAl and YbAgGe. |
Wednesday, March 7, 2018 12:03PM - 12:15PM |
L44.00005: High Pressure Investigations on the Semi-Heusler Compound CuMnSb Pallavi Malavi, Jing Song, Wenli Bi, Alexander Regnat, Andreas Bauer, Anatoliy Senyshyn, Christian Pfleiderer, James Schilling Half metallic Heusler alloys in which charge carriers are in spin polarized states form an intensively studied class of magnetic materials. CuMnSb is a rare example of an AFM Mn-based member among the semi-Heusler compounds with a relatively low Néel temperature near 50K. We investigated polycrystalline CuMnSb under high pressure by four-point electrical resistivity measurements in the temperature range 5-295K to 50GPa as well as synchrotron x-ray diffraction at ambient temperature to 30GPa. Up to 7GPa, pressure is found to enhance the Néel temperature. Above this pressure the temperature dependence of the resistivity shows a dramatic change associated with a first-order structural transition from cubic to a lower symmetry structure. The diffraction peaks of the high pressure phase are significantly broadened, suggesting its metastable nature. In a second x-ray experiment the diamond-anvil-cell was heated resistively to 350oC to complete the phase transition. Our study highlights the importance of pressure as a tool to explore novel electronic and structural phases in this interesting magnetic material. |
Wednesday, March 7, 2018 12:15PM - 12:27PM |
L44.00006: Tuning Competing Ground States in LuFe4Ge2 Using External Pressure Ajeesh Mukkattu Omanakuttan, Shanu Dengre, Rajib Sarkar, Philipp Materne, Katharina Weber, Ricardo dos Reis, Rustem Khasanov, Sergey Medvedev, Vadim Ksenofontov, Hans-Henning Klauss, Christoph Geibel, Michael Nicklas Exotic phenomena and unconventional phases occur at regions of competing energy scales in correlated materials, especially in systems with magnetic frustration. Here, we investigate LuFe4Ge2 under external pressure in order to better understand the interplay between competing ground states. LuFe4Ge2 is a frustrated, itinerant magnetic system with antiferromagnetic (AFM) ordering accompanied by a structural transition at 36 K. The pressure dependence of the magneto-elastic transition in LuFe4Ge2 has been investigated using electrical transport, ac magnetic susceptibility, X-ray diffraction, Mössbauer, and muon-spin resonance (μSR) measurements under external pressure. External pressure suppresses the first-order magnetic transition (AFM1) at around 1.8 GPa, while the structural transition is largely unaffected by pressure. A new pressure-induced magnetic phase is confirmed by Mössbauer and μSR experiments. Mössbauer investigations indicate that the high pressure phase is also antiferromagnetically ordered (AFM2), with a different size of the ordered moment and/or a different magnetic structure. Further studies to understand the pressure-induced phase and the interplay between magnetic and structural phase transitions are under way. |
Wednesday, March 7, 2018 12:27PM - 12:39PM |
L44.00007: Orbital ordering in the iron-ladder material BaFe2S3 studied by elastoresistance measurements Suguru Hosoi, Kousuke Ishida, Yuta Mizukami, Satoshi Imaizumi, Kazuki Hashizume, Takuya Aoyama, Yoshinori Imai, Kenya Ohgushi, Takasada Shibauchi BaFe2S3 is one of the most attractive materials in that superconductivity appears in the vicinity of bandwidth-control type Mott transition under high pressure. At ambient pressure, BaFe2S3 is a semiconductor with antiferromagnetic ordering at TN ~ 110 K and another transition at around T* ~ 200 K characterized by a small anomaly in resistivity. One of the speculations is that orbital degrees of freedoms play an important role in this unidentified transition, and there is a suggestion of a possible orbital order similar to the nematic order in iron-based superconductors with Fe square lattice. Elastoresistance under uniaxial strain is a powerful tool to elucidate the nature of orbital ordering through the evaluation of its nematic fluctuations. Here we apply this elastoresistance technique to BaFe2S3 and investigate temperature dependence of putative orbital fluctuations. Our elastoresistance measurements reveal a clear anomaly at T* consistent with resistivity measurements, indicating the presence of electronic phase transition. |
Wednesday, March 7, 2018 12:39PM - 12:51PM |
L44.00008: Abstract Withdrawn
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Wednesday, March 7, 2018 12:51PM - 1:03PM |
L44.00009: Multiple Magnetic Orders in the Three-dimensional Phase Diagram of CeAuSb2 under Magnetic Field and Pressure Soonbeom Seo, Sean Thomas, Filip Ronning, Eric Bauer, Joe Thompson, Priscila Rosa CeAuSb2 is a heavy-fermion antiferromagnet in which the antiferromagnetic transition temperature TN is suppressed by a modest c-axis magnetic field. With pressure, however, new magnetic phases emerge hindering the appearance of a pressure-induced quantum critical point. At ambient pressure, two metamagnetic transitions are observed at Hc1 ~ 2.8 T and Hc2 ~ 5.6 T. A recent neutron scattering study shows that the transition of magnetic structure occurs at Hc1 from a striped to a woven spin density wave. We report the magnetic field-pressure-temperature phase diagram of CeAuSb2 derived from the temperature and field dependence of electrical resistivity under pressure. Above 2.24 GPa, TN splits into two transitions which are connected to the metamagnetic transitions in the temperature-field phase diagram. We will discuss these multiple magnetic orders and critical points in the three-dimensional phase diagram. |
Wednesday, March 7, 2018 1:03PM - 1:15PM |
L44.00010: Giant magnetoresistive effects in antiferomagnetic semiconductors BaMn2Pn2 (Pn = As, Sb, Bi) Khuong Huynh, Takuma Ogasawara, Keita Kitahara, Takuya Aoyama, Kenya Ohgushi, Taimu Tahara, Takanori Kida, Masayuki Hagiwara, Katsumi Tanigaki In this talk, we report the intriguing giant negative magnetoresistive effects observed in BaMn2Pn2 compounds, in which Pn stands for the pnictogens As, Sb, and Bi. These materials adopts identical (122) crystallographic and G-type antiferromagnetic structures and can be very interesting from the view point of symmetry. Here the magnetic point group 4’/m’mm’ directly suggests the existence of a diagonal dissipative magnetoelectric effect confined in the ab plane of the crystals. Importantly, by changing the Pn elements, both spin-orbit coupling and pd hybridization can be tuned without disturbing the symmetry. |
Wednesday, March 7, 2018 1:15PM - 1:27PM |
L44.00011: Anomalous Hall Effect in a Noncentrosymmetric Antiferromagnet CoNb3S6 Nirmal Ghimire, Antia Botana, Junjie Zhang, Yu-Sheng Chen, J Jiang, John Mitchell An ordinary Hall effect in a conductor arises due to the Lorentz force acting on the charge carriers. In ferromagnets, an additional contribution to the Hall effect, which is proportional to the magnetization, appears and is termed as the Anomalous Hall effect (AHE). Such an anomalous Hall effect is not seen in a collinear anitferromagnet with zero net magnetization. However, recently it has been shown that intrinsic part of the AHE can be non-zero in non-collinear antiferromagnets as well as in topological materials hosting Weyl nodes near the Fermi energy. We have recently found a large anomalous Hall effect with Hall conductivity of 30 Ω-1 cm-1 in a collinear antiferromagnet CoNb3S6 with a non-centrosymmetric crystal structure. It orders below 27.5 K with the moments lying in the ab-plane. Magnetization measurement shows the presence of a small ferromagnetic component (0.0013 Bohr magnetons) along c-axis. The large AHE, observed only for H || c, is difficult to reconcile in light of the small ferromagnetic component. Here I will discuss potential alternative explanations of the AHE in CoNb3S6 framed in terms of topological band structure features or spin texture. |
Wednesday, March 7, 2018 1:27PM - 1:39PM |
L44.00012: Electronic band structure study of binary MnP-type CoAs under pressure Limin Wang, Daniel Campbell, Johnpierre Paglione The transition metal-pnictide binary materials such as CrAs and RhAs have attracted theoretical and experimental interest due to their intriguing magnetic and superconducting states at low temperatures and high pressures. The metallic binary pnictide FeAs exhibits an intriguing incomensurate spin-density wave ordered state below 70 K that remains to be explained, while its related cousin CoAs is paramagnetic and metallic. We will present full structure optimization calculations under as a function of pressure to investigate the ground state stability of CoAs and its relation to experimental results on single-crystal specimens of FeAs, CoAs and related binary pnictides. |
Wednesday, March 7, 2018 1:39PM - 1:51PM |
L44.00013: Healing of defects in random antiferromagnetic spin chains Romain Vasseur, Arash Roshani, Stephan Haas, Hubert Saleur We study the effects of a weakened link in random antiferromagnetic spin chains. We show that healing occurs, and that homogeneity is restored at low energy, in a way that is qualitatively similar to the fate of impurities in clean ferromagnetic spin chains, or in Luttinger liquids with attractive interactions. Healing in the random case occurs even without interactions, and is characteristic of the random singlet phase. Using real space renormalization group and exact diagonalization methods, we characterize this universal healing crossover by studying the entanglement across the weak link. We identify a crossover healing length L* that separates a regime where the system is cut in half by the weak link from a fixed point where the spin chain is healed. Our results open the way to the study of impurity physics in disordered spin chains. |
Wednesday, March 7, 2018 1:51PM - 2:03PM |
L44.00014: Dualities and Ground State Phase Diagrams for Quantum Spin-s XYZ Models Qian-Qian Shi Dualities and ground state phase diagrams are discussed for quantum XYZ chains with arbitrary spin s. It is shown that dualities reproduce the ground state phase diagrams for quantum half-integer spin XYZ chains, such as spin s=1/2, 3/2, but not for quantum integer spin XYZ chains, such as spin s=1, 2, in which the so-called symmetry protected topological phase--Haldane phase occurs. Dualities discussed for the one-dimensional quantum XYZ chains with aritrary spin s may be extended to quantum XYZ models with arbitrary spin s on a bipartite lattice in any spatial dimensions, such as square and honeycomb lattices. |
Wednesday, March 7, 2018 2:03PM - 2:15PM |
L44.00015: Electronic Structure and Magnetic Character of Antiferromagnetic Compound NpPt2In7 Agnieszka Kozub, Klimczuk Tomasz, Alexander Shick A very important class of materials, the AnMmIn3n+2m family, where M is a group 9 transition metal and A=Ce, U, Np or Pu, offers to explore the relationship between unconventional superconductivity and magnetism. In this work, we present a theoretical study of a Np-based member of this family, an antiferromagnetic compound NpPt2In7, analogue of heavy-fermion superconductor under pressure CePt2In7. We focus on its electronic structure and determine computationally the magnetic character. Calculations were performed in the framework of the relativistic density functional theory (including the spin-orbit coupling) plus Coulomb-U (DFT+SOC+U) using a full-potential linearized augmented plane-wave (FP-LAPW) basis. DFT(+SOC) yields the correct antiferromagnetic (AF) ordering, but fails to reproduce the experimentally observable 2.53 µB magnetic moment on Np. The correlated method DFT+SOC+U(AMF) improves the Np-atom magnetic moment over DFT. Also, the calculations produce the AF ground state in agreement with experiment. It indicates fairly localized character of the Np-f-shell in NpPt2In7. |
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