Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q53: Magnetism in Correlated Electron Systems II: Experiment & TheoryRecordings Available
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Sponsoring Units: GMAG DCMP Chair: Saikat Banerjee, Los Alamos National Laboratory Room: McCormick Place W-475B |
Wednesday, March 16, 2022 3:00PM - 3:12PM |
Q53.00001: RKKY coupled local-moment magnetism in NaFe1-xCuxAs Yizhou Xin, Ingrid Stolt, Zhai Gan, William P Halperin, Yu Song, Pengcheng Dai, Chongde Cao Using high resolution 23Na NMR measurements on lightly Cu-doped metallic single crystals of NaFe1-xCuxAs (x ≈ 0.01) and numerical simulation, we present direct evidence of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in this pnictide system. The magnetic Cu2+ impurities are polarized by external field, inducing a spin polarization of the conduction electrons. Aided by computer simulation, we identify the 23Na NMR satellite resonances with the RKKY oscillations of this spin polarization coupled to loal moments at Fe sites via exchange interaction. Our 23Na spin-lattice and spin-spin relaxation data exhibits signature of an itinerant and inhomogeneous AFM phase in this system. Our NMR results indicate coexistence of local and itinerant magnetism in lightly Cu-doped NaFe1-xCuxAs. |
Wednesday, March 16, 2022 3:12PM - 3:24PM |
Q53.00002: Magnetic and transport properties of RMn6Sn6 (R=Er, Ho) kagome magnet Jacob Casey, Randall Filippone, Narayan Poudel, Madhab Neupane, Krzysztof Gofryk, Pietro Manfrinetti, Arjun K Pathak Materials that possess interplays between magnetism, correlation, and band topology often result in various exotic topological phenomena, such as giant anomalous Hall effect, Dirac fermions with large magnetic field tunability, magnetic Weyl semimetal state, and Chern gapped Dirac fermions. Rare earth intermetallic compound, RMn6Sn6, is among the most interesting kagome systems to study intrinsic quantum behavior. In this presentation, we will discuss the phase transition, and effect of external stimuli such as temperature, magnetic field, and pressure on magnetic, thermal and transport properties for RMn6Sn6 (R=Er, Ho). Compared with HoMn6Sn6, ErMn6Sn6 shows an anomalously large Hall effect and complex magnetism. In addition, the experimental results show that RMn6Sn6 is extremely sensitive to applied physical pressure. We will compare the magnetic and transport behaviors for Er and Ho-based kagome magnets. |
Wednesday, March 16, 2022 3:24PM - 3:36PM |
Q53.00003: Moment un-freezing in iridium substituted Sr2RuO4 Zachary Porter, Stephen D Wilson We report data suggestive of a J-freezing metallic quantum critical point in paramagnetic Sr2IrxRu1-xO4. Electron doping from the d4 compound Sr2RuO4 though a transition near x=18% yields an abrupt increase in the static effective moment magnitude as well as the antiferromagnetic fluctuations. We present thermodynamic measurements of high-quality floating-zone-synthesized single crystal samples. Our findings may indicate a novel critical point neighboring the nonmagnetic ground state of the correlated metal Sr2RuO4. |
Wednesday, March 16, 2022 3:36PM - 3:48PM |
Q53.00004: Robust antiferromagnetism in NaOsO3 under pressure Prasun Boyal NaOsO3 is known to be an insulator with a small band gap of 0.2 eV, favoring a G-type antiferromagnetic state below 410 K. It is believed to be an example of a Slater insulator [1], with spin-orbit interactions playing a significant role here in modifying the electronic structure[2]. The unusually high antiferromagnetic temperature has been explained as emerging from the half-filling of the t2g state [3]. We have examined the pressure dependence of the electronic structure, as well its evolution under pressure both in the presence and absence of spin-orbit interactions within ab-initio electronic structure calculations. Mapping the Hamiltonian to a tight-binding model, we use pressure as a parameter to tune the interaction strengths and bring it to the point where magnetic order just sets in. This allows us to throw light on the mechanism of magnetism. |
Wednesday, March 16, 2022 3:48PM - 4:00PM |
Q53.00005: First-principles studies of the role of stoichiometry on electronic structure of BaBi1-xPbxO3 Sijia Ke, Jonah B Haber, Jeffrey B Neaton BaBi1-xPbxO3 has been extensively studied for decades for its intriguing electronic properties including superconductivity, charge density waves, large topological gaps, and metal-to-insulator transitions. However, a thorough investigation of Bi and Pb site energetics and local structure, and associated electronic structure, of this compound for different x is lacking. Using density functional theory-based methods, we compute the electronic structure and spin-dependent properties of low-energy arrangements of Bi and Pb, relating local distortions, nominal oxidation state, and presence of disproportionation to the nature of the band structure and the orbital character near the Fermi energy. We discuss the implications of our calculations on how the concentration, arrangement, and nature of the Bi and Pb sites affect BaBi1-xPbxO3 transport properties. |
Wednesday, March 16, 2022 4:00PM - 4:12PM |
Q53.00006: Origin of Insulating Ferromagnetism in Iron Oxychalcogenide Ce2O2FeSe2 Ling-Fang Lin, Yang Zhang, Gonzalo Alvarez, Adriana Moreo, Elbio R Dagotto The mechanism of magnetic exchange in transition metal compounds continues attracting the attention of the condensed matter community. An insulating ferromagnetic (FM) phase exists in the quasi-one-dimensional iron oxychalcogenide Ce2O2FeSe2, but its origin is unknown [1]. To understand the FM mechanism, here a systematic investigation of this material is provided, analyzing the competition between ferromagnetic and antiferromagnetic tendencies and the interplay of hoppings, Coulomb interactions, Hund’s coupling, and crystal-field splittings. Our intuitive analysis based on density functional theory (DFT) calculations and second-order perturbation theory show that large entanglements between doubly occupied and half-filled orbitals play a key role in stabilizing the FM order in Ce2O2FeSe2. In addition, via density matrix renormalization group (DMRG) computational techniques applied to a multiorbital Hubbard model, the phase diagram confirms the proposed FM mechanism [2]. |
Wednesday, March 16, 2022 4:12PM - 4:24PM |
Q53.00007: Existence of La-site antisite defects in LaMO3 (M=Mn, Fe, Co, and Ni) predicted with many-body diffusion quantum Monte Carlo Tom Ichibha, Kayahan Saritas, Jaron T Krogel, Ye Luo, Paul Kent, Fernando A Reboredo The properties of LaMO3 (M: 3d transition metal) perovskite crystals are significantly dependent on point defects. The most studied defects in La perovskites are the oxygen vacancies and doping impurities on the La and M sites. Based on results of an accurate many-body and ab initio theoretical approach, here we suggest that another intrinsic antisite defect, the replacement of lanthanum by the transition metal, M, can be formed under certain growth conditions. Fixed-node diffusion Monte Carlo (FNDMC) calculations of LaMO3 (M=Mn, Fe, Co, and Ni) find that such antisite defects can have low or negative formation energies and are magnetized. Complementary density functional theory (DFT) based calculations show that these antisite defects improve the p-type electronic conductivity. Our bulk validation studies establish that FNDMC reproduces the antiferromagnetic (AFM) state of LaMnO3, while DFT with PBE and SCAN functionals and LDA+U method all favor ferromagnetic (FM) states, in variance with experiment. For LaNiO3, the experiments have reported the antiferromagnetic (AFM) or non-magnetic (NM) ground state. Our FNDMC predict that R-type AFM state and FM state (1 bohr/f.u.) are equally stable: E(FM)-E(AFM)=-0.036(26) eV/f.u. |
Wednesday, March 16, 2022 4:24PM - 4:36PM |
Q53.00008: Mechanism of ferro-octupolar interaction in Osmium double-perovskites Derek Churchill, Hae-Young Kee In 5d2 Mott insulators with strong spin-orbit coupling, the lowest pseudospin states form a non-Kramers doublet which carries quadrupolar and octupolar moments. A family of double-perovskites, where the magnetic ions form a face-centered cubic (FCC) lattice, was suggested to unveil an octupolar order offering a rare example in d-orbital systems. The proposed order requires a ferromagnetic (FM) octupolar interaction, since the antiferromagnetic (AFM) Ising model is highly frustrated on the FCC lattice. Here we study a microscopic mechanism to generate a FM octupolar interaction. We find that the interference of two intra-orbital exchanges generates a FM octupolar interaction and higher order exchange processes connecting the non-Kramers doublet to an excited triplet further enhances the FM octupolar interaction. Applying the strong-coupling expansion results together with tight binding parameters obtained by density functional theory, we present the exchange interactions for several Osmium double-perovskites and discuss implications of our theory to experimental results. |
Wednesday, March 16, 2022 4:36PM - 4:48PM |
Q53.00009: Theory of itinerant magnetism in the infinite U Hubbard model Kyung-Su Kim, Chaitanya Murthy We develop a perturbation theory in the strong coupling limit of Hubbard model in one dimension and derive effective magnetic interactions. Importantly, this theory works for any electron density away from 0. The derived magnetic interaction is ferromagnetic or antiferromagnetic depending on the signs of the hopping integrals. In the former case, this shows the robustness of Nagaoka ferromagnetism for a finite density of doped holes—we believe this to be the first demonstration of its relevance in the thermodynamic limit. We also present the magnetic phase diagram obtained from density matrix renormalization group calculations, which corroborates our conclusions. Finally, we comment on higher dimensional generalizations. |
Wednesday, March 16, 2022 4:48PM - 5:00PM |
Q53.00010: Unconventional magnetic order emerging from competing energy scales in the new RRh3Si7 intermetallics (R = Gd-Yb) Long Qian, Shiming Lei, Binod K. Rai, Chien-Lung Huang, Alannah M. Hallas, Greogory T. McCandless, Julia Y. Chan, Emilia Morosan The competition between Ruderman-Kittel-Kasuya-Yosida (RKKY), crystal electric field (CEF), and Kondo energy scales is known to give rise to complex magnetism in many rare earth-based intermetallics. In this talk I will focus on the hard axis magnetic ordering, where the magnetic moment orders along the hard CEF axis, in the RRh3Si7 series of compounds (R = Gd - Yb). We compare the influence of each energy scale on the magnetic order, by studying the members with only RKKY interactions (R = Gd), both RKKY and CEF effects (R = Tb-Tm), and with all three interactions (R = Yb). Beyond the RRh3Si7 series , we extended the comparison to other isostructural Kondo systems, YbIr3Si7 [1] and YbIr3Ge7 [2], where the hard axis magnetic order is also observed. We find that the non-Kondo RRh3Si7 compounds do not show the hard axis magnetic order, while this does occur in all three Kondo systems YbRh3Si7, YbIr3Si7 and YbIr3Ge7, suggesting the crucial role of Kondo effect in hard axis magnetic ordering. Aside from Kondo effect, the CEF-RKKY competition causes complex magnetic ground states, showing entangled magnetic and electronic degrees of freedom in all compounds of the family. |
Wednesday, March 16, 2022 5:00PM - 5:12PM |
Q53.00011: Strain induced electronic structure, and magnetic and structural properties in quaternary Heusler alloys ZrRhTiZ (Z?=?Al, In) Ram B Ray, Gopi C Kaphle, Raj K Rai, Dinesh K Yadav, Ramesh Paudel, Durga Paudyal Electronic structure, and magnetic and structural properties of quaternary Heusler alloys ZrRhTiZ (Z?=?Al, In) have been analyzed from first principles calculations. The ferromagnetic ground state and thermodynamical stability of these compounds are supported by relative total energies, and by derived formation and cohesive energies, respectively. The investigated Curie temperatures of the compounds exceed room temperature indicating that these compounds are promising candidates for beyond room temperature spintronics and magneto-electronics applications. Both compounds follow the Slater-Pauling 18 electron rule and exhibit half-metallic ferromagnetic behavior with magnetic moments of 2 μB with 100% spin polarization in one spin channel at the Fermi-level. The effect of uniform strain on half-metallicity of these compounds inverts the band gap from one spin channel to another spin channel with a mixed spin (magnetic moment) regime that can be mapped to an exchange bias like effect observed in some of the magnetic Heusler compounds. The half metallic ferromagnetic behavior is retained within −2 to 2% strain contrasting with the anomalous spin flip in −1% and 1% strain in ZrRhTiZ (Z?=?Al, In). |
Wednesday, March 16, 2022 5:12PM - 5:24PM |
Q53.00012: Re-examining the giant magnetization density in α′′-Fe16N2 with the SCAN +U formalism Assa Aravindh Sasikala Devi, Johannes S Nokelainen, Bernardo Barbiellini, Murali Devaraj, Arun Bansil, Matti Alatalo
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Wednesday, March 16, 2022 5:24PM - 5:36PM |
Q53.00013: Understanding the complex magentism in Ce2Fe17 from ab initio methods Heike C Herper, Alena Vishina, Olle Eriksson The high magnetization and the low costs have made the intermetallic Ce2Fe17 an attractive candidate for permanent magnets. Its low Curie temperature (TC) and basal plane magnetocrystalline anisotropy can be cured by doping with light elements. Despite this no full understanding of the magnetism of Ce2Fe17 has been achieved so far. Though a large number of partially seemingly contradicting findings exist theoretical studies are sparse and do not capture the experimental findings. We have performed a comprehensive study of the magnetism of Ce2Fe17 investigating carefully the best theoretical treatment of the system e.g. by applying various approaches for the exchange-correlation functional. To account for the mixed valent nature of Ce2Fe17 several approximations were tested including an analysis of the hybridization function as proposed in [1]. We used a combination of ab initio codes to obtain structural and magnetic data including magnetic exchange parameters. The later were used in Monte Carlo simulations [4] to determine TC. |
Wednesday, March 16, 2022 5:36PM - 5:48PM |
Q53.00014: A first principles based investigation of magnetism and Mott transition in correlated Ba2Fe1- pXpMoO6 (X=Mn,Ni,Cu,Zn) double perovskites Suman Mondal, Krishnaraj Kundavu, Amrita Bhattacharya Oxide double perovskites have been extensively studied for a wide range of applications ranging from spintronics to semiconducting devices. In d-group oxide double perovskites the correlated nature of electrons may give rise to metal to insulator transitions which may exhibit exotic properties like Giant and Colossal magnetoresistance (CMR and GMR). In this study, we explore the structural, electronic and magnetic properties of the double perovskites Ba2Fe1- pXpMoO6 (X=Mn,Ni,Cu,Zn). A systematic investigation is performed within the GGA+U approximation of Density Functional Theory (DFT), which shows the compositionally controlled metal to insulator transition with alloying in Fe-Mn and and Fe-Zn double perovskites. More precisely, a Mott transition is observed in the case of Fe-Mn alloys, while for the Fe-Zn system a complete insulating behaviour is observed above 50% Zn substitution. On the other hand, for the Fe-Cu and Fe-Ni systems, a half-metallic behavior is observed throughout the compositional space. We analyse the magnetic ordering of these phases in details. Ba2Fe0.5Mn0.5MoO6 is predicted to be a ferromagnetic insulator in our study suggesting its use in spintronic applications. |
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