Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session K55: Nanomagnetic Core Shell Structures and Antiferromagnetic Systems |
Hide Abstracts |
Sponsoring Units: GMAG DMP Chair: Abdelghani Laraoui, University of Nebraska - Lincoln Room: Room 305 |
Tuesday, March 7, 2023 3:00PM - 3:12PM |
K55.00001: Conditions for the symmetry-compensated magnets to show altermagnetic properties Igor I Mazin, Andriy Smolyanuk, Olivia Taiwo Discovered in ~2019 phenomenon of spin-split nonrelativistic bands in a compensate antiferromagnet created a unique situation where an entire class of materials that would’ve been classified as antiferromagnets (AFM) exhibits most of the ferromagnetic signatures: anomalous Hall effect, MOKE, etc. Since this discovery was made independently and concurrently by at least four groups, they were alternatively called “spin-split AFM”, “Anti-Kramers AFM”, and “Altermagnets (AM)”. Here we adapt the latter term, suggested by the Mainz spintronics group. One of the urgent challenges is creating a simple tool that would allow experimentalists quickly test, knowing the structure and magnetic pattern, whether a newly synthesized, or revisited, material is AF or AM. To this end, we prove three theorems that allowed us to encode a simple protocol for immediate determination of the AF/AM status. The required input is: (1) the space group # and (2) the list of Wyckoff positions (WP) occupied by magnetic species (usually just one) and, for a multiplicity >2, the up-down spin partitioning. They are: |
Tuesday, March 7, 2023 3:12PM - 3:24PM |
K55.00002: Experimental and Theoretical Studies of CdSe/CdMnS core/shell nanaoplatelets in variable magnetic fields James M Pientka, Arinjoy Bhattacharya, Peiyao Zhang, Savas Delikanli, Furkan Isik, Hilmi Volkan Demir, Xiang Zhang, Athos Petrou We performed time-resolved photoluminescence (PL) studies of colloidal nanoplatelets (NPL) samples at temperatures (T=5,10 K) in the presence of a magnetic field B that is perpendicular to the NPL planes. We performed the experiments on two NPL samples, samples A and B. Samples (A/B) have a CdSe core (5ML/5ML) surrounded by a CdMnS(2ML/2ML) and CdS (4ML/8ML) shell. The band-edge emission time evolution cn be described by two-time constants for both samples. A fast recombination time which is excitonic and a slow recombination that involves electrons with holes localized at the CdSe/CdMnS interfaces. Both time constants depend on the externally applied magnetic field. A theoretical model was developed to interpret these results. [1] J.R. Murphy et al., Appl. Phys. Lett. 2016, 108, 242406 |
Tuesday, March 7, 2023 3:24PM - 3:36PM |
K55.00003: Syntheses, magnetic and structural properties of core-shell FePc and FePr nanoparticles annealed by oxygen and nitrogen at different temperatures Armen Kocharian, Franco Iglesias, Calixto Alvarado, Armond Khodagulyan, Oscar Bernal, Jeffrey Shallenberger, Nicole Wonderling In recent years there is a growing interest in synthesizing of novel iron-based nanoparticles and nanocomposites with high efficiency of thermal energy transfer suitable for use in magnetic fluid hyperthermia. Oxygen and nitrogen annealed phthalocyanine and porphyrin (graphene) can significantly influence magnetic properties as compared with those of pyrolysis of iron based graphene. We investigate structural and magnetic properties of synthesized by a one-step process of thermal decomposition (Pyrolysis) of iron phthalocyanine (FePc) and iron porphyrin (FePr) nanoparticles of “core-shell” structure with the high magnetic moment of core (such as Fe), and the shell consists of a biocompatible material (e.g. iron oxide, iron nitride or carbide). We conducted investigations of structural and magnetic properties of these materials annealed by oxygen and nitrogen at different temperatures using X-ray diffraction (XRD), measurements of XPS spectra, high resolution SEM/STEM images, magnetometry PPMS measurements. The oxygen and nitrogen content and structures are directly achieved from the XPS analysis. The measured magnetization of magnetic saturation and coercivity as well as the specific absorption rate (SAR) show that these materials attractive for magnetic hyperthermia medical applications. Hysteresis loop of the (Fe-Fe3C)@C and (Fe-Fe3O4)@C nanocomposites are of special interest because of high Mr/Ms ratio. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K55.00004: Preparation of nanoengineered ZVI@CIT core-shell with ultra-high magnetic saturation and tunable magnetic properties as candidates for treatment water, biomedical, and energy applications Yohannes W Getahun, Debabrata Das, Chintalapalle V Ramana, Ahmed A El Gendy Crystalline zero-valent iron (cZVI) has generated a great deal of interest in recent years due to its potential in water treatment, biomedical and energy applications with enhanced performance at lower magnetic field gradients. To find out candidates for water treatment, hyperthermia, and in energy applications as anode materials in lithium-ion batteries, as catalysts in oxygen evolution reactions, and for oil purification, the present study demonstrates synthesis and elucidation of ZVI) based core-shell nano-systems prepared at various temperatures, concentrations of the core metal, ligand and reducing agent. We found out that, at optimal metal concentrations, magnetic saturation increases with an increase in concentrations of capping and reducing agents but decreases as the temperature of the reaction increases. Particles have an average size (DSEM = 39±13 nm) with a spherical shape. Ultra-high magnetic saturation (241 emu/g) observed in response to low reaction temperature is associated with the relaxation of magnetization behavior. Hence, we demonstrate the tunability of magnetization in ZVI@CIT core-shell nanoparticle systems. This work uncovers essential information on tuning magnetization and crystal properties of nano-scale core-shell particles for the purpose of using them in various applications. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K55.00005: Magneto-Electric Effects in Core-Shell Nanofibers of Nickel Zinc Ferrite and PZT Gopalan Srinivasan, Bingfeng Ge, Jiahui Liu, Jitao Zhang The nature of mechanical strain mediated magneto-electric (ME) interactions is investigated in coaxial nanofibers of nickel zinc ferrite and PZT synthesized by electrospinning. Fibers of core diameter 100-200 nm and shell thickness of 100-250 nm with (1-x) Ni xZn Fe2O4 (x = 0.5-0.9) (NZFO) and PZT were made from sols of the ferrite and PZT. For comparison of ME properties, we also synthesized composite fibers with ferrite and PZT by mixing the two sols. Fibers annealed at 700-900 C were found to be free of impurity phases and electron and scanning probe microscopy revealed core-shell structure for the coaxial fibers. Ferroic order parameters for the core-shell and composite fibers were an order of magnitude smaller than for bulk materials. The strength of ME interactions were measured in disks of fibers by magnetic field H induced change in polarization P and by low-frequency ME voltage coefficient (MEVC). The fractional change in P for H=7 kOe in core-shell fibers ranged from 3% to 82% with disks of Ni-Zn ferrite with x=0.3 showing the maximum value and were much higher than for composite fibers. The maximum MEVC for core-shell fibers was 17 mV/cm Oe and was an order of magnitude higher than for composite fibers. The coaxial fibers are of importance for use as magnetic sensors and in energy harvesting applications. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K55.00006: Microscopic mechanism for intrinsic nonlinear Hall conductivity in noncollinear antiferromagnetic metals Akimitsu Kirikoshi, Satoru Hayami Nonlinear responses in magnetic materials have recently been attracted, since they are induced by the interplay between magnetism and topology. In particular, we focus on the second-order electric conductivity in the antiferromagnetic (AFM) metals with space-time symmetry, where two contributions, the Drude and intrinsic terms, are important. The former is induced by an antisymmetric band modulation resulting from the effective coupling between magnetic ordering and antisymmetric spin-orbit interaction (ASOI), while the microscopic mechanism for the latter has not been fully elucidated. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K55.00007: Observation of antiferromagnetism in Nickel monosilicide Pousali Ghosh, Deepak K Singh, Jiasen Guo, Tom Heitmann, Feng Yi, George Yumnam, Kelley Steven, Vitalii Dugaev, Arthur Ernst Over the past decades, discoveries of unconventional properties of antiferromagnets, such as in Mn3Si, FeGe, etc., have made them very interesting candidates for spin-based technologies and applications. Nickel monosilicide, an important intermetallic system, significantly used as interconnects in nanoelectronic devices, has never been reported to have magnetic order despite the presence of Ni. Non-trivial temperature dependences of both nuclear positions as well as odd reciprocal lattice positions have been observed from elastic neutron diffraction measurements on our home-grown NiSi sample, indicating the existence of an uncompensated antiferromagnetic order with an onset temperature of 700K, in the system. On applying magnetic field perpendicular to the direction of the non-compensated moments, hysteresis behavior is observed with a one-step switching characteristic at a very small critical field of H ~ 900 Oe. This abrupt transition observed both at T = 350K and T =20K, accounts for switching between two distinct minimum energy ferromagnetic spin configurations. The evidence of the uncompensated antiferromagnetism is also observed in the non-zero hall resistance at H = 0T, along with magneto-electronic hysteresis for both longitudinal and Hall resistances at high temperatures indicating a complex behavior that has been explored for the very first time in this system. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K55.00008: Magnetocrystalline anisotropy of epitaxial MnPt thin-films David D Nelson, Mara Mishner, Ilya N Krivorotov Antiferromagnetic (AFM) spintronics is a promising path towards ultrafast scalable information storage and processing technologies. Yet quantitative knowledge of key material parameters for many AFMs is lacking due to the difficulty of controlling the AFM order parameter. Here we demonstrate that measurements of the angular dependence of ferromagnetic resonance (FMR) in MnPt/ Ni80Fe20 bilayers allow us to probe magnetocrystalline anisotropy of the MnPt AFM. For this study, epitaxial L10-Mn50Pt50 films in the thickness range from 6 nm to 22 nm were grown onto a MgAl2O3 (100) substrates, followed by deposition of polycrystalline Ni80Fe20 as the ferromagnetic (FM) coupling layer. FMR measurements reveal a 4-fold in-plane anisotropy in Ni80Fe20 imparted from the MnPt layer by the interlayer exchange coupling. An analytical model of exchange coupling in FM/AFM bilayers was used to show that the observed anisotropy in the FM layer directly relates to magnetocrystalline anisotropy in the coupled AFM. Analysis of the dependence of the induced 4-fold anisotropy on the AFM layer thickness allows us to quantify the magnetocrystalline anisotropy of MnPt. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K55.00009: Magnetic instability and frustration controlled with competing spin and exchange parameters in compositionally complex correlated oxides Zac Ward, Alessandro R Mazza, Elbio R Dagotto, Matthew Brahlek Exchange and spin disorder provide access to quantum criticality, frustration, and spin dynamics, but broad tunability and a deeper understanding of strong limit disorder is lacking. A range of single crystal high entropy oxide La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 films are synthesized to probe the role of site-to-site spin and exchange interaction variances in stabilizing magnetic responses. The complexity of the system provides tunability and functionality not present in any of the ternary or half-doped quaternary parents or as a sum of parent properties. Neutron diffraction and magnetometry show that the compositionally disordered systems can paradoxically host long-range magnetic order, while manipulation of the S and J parameters through cation ratio permits continuous control of magnetic phase from antiferromagnetism (AFM), to degenerate, to ferromagnetism (FM). Tuning of the coexisting magnetic phase composition allows design of exchange bias behaviors in monolithic single crystal films, which have, until now, only been observable in AFM-FM bilayer heterojunctions or 2D layered bulk systems. The effects of hole doping on the A-site sublattice and “exchange interaction” doping the B-site sublattice will be discussed. |
Tuesday, March 7, 2023 4:48PM - 5:00PM |
K55.00010: Competing Magnetic Anisotropies in the Antiferromagnet Thin Film Alloy Ni1-xMnxF2 Ryan T Van Haren, Vanessa Hald, David Lederman NiF2 and MnF2 both have a rutile crystal structure and antiferromagnetic (AF) order at low temperature, but NiF2 has an easy-plane plane anisotropy with an effective Dzyaloshinskii-Moriya interaction, while MnF2 is an easy axis uniaxial anisotropy. Bulk NiF2 orders at 73 K and prefers to orient the AF spins along the [100] or [010] directions, while bulk MnF2 orders at 67 K with an easy axis anisotropy that orients the spins along the [001] direction. The close structural similarity and relatively small lattice mismatch between the NiF2 and MnF2 crystals makes them good candidates for a mixed thin film alloy system with competing AF anisotropies. I will present our work growing and characterizing thin film Ni1-xMnxF2 alloys, a system which to date has not been studied. These alloys represent a system with competing single-ion AF anisotropies without frustration due to the exchange interaction. Thin films of varying stoichiometries were grown via MBE and characterized with x ray diffraction (XRD), which showed that the alloys grow epitaxially and single phase along the [110] direction. XRD measurements also show a smooth change of the lattice constants as the stoichiometry is changed and strain due to epitaxial growth on the MgF2 (110) substrate. The magnetic moment of these samples was measured and used to determine the magnetic anisotropy of the alloys, demonstrating that the easy axis flips near x = 0.7, and the effect of strain on transition temperature. |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K55.00011: Electronic transport of Mn2-xZnxSb Md Rafique Un Nabi, Rabindra Basnet, Gokul Acharya, Dinesh Upreti, Santosh Karki Chhetri, Jin Hu Mn2Sb and MnZnSb are characterized in a Cu2Sb-type tetragonal layered structure but exhibit different magnetic and transport properties. Mn2Sb displays a ferrimagnetic order below Tc ∼ 550K with magnetic moments aligned collinearly along the c-axis. It undergoes another phase transition around 240K characterized by a spin rotation toward the ab plane. We successfully grew Mn2-xZnxSb (0≤X≤1) single crystals and characterized their magnetic and electronic transport properties. We found interesting evolution of electronic transport with varying the Zn content: The Zn-rich samples display a non-metallic behavior, whereas metallic transport is observed in Zn-less samples. Such unusual evolution is likely attributed to the coupling between transport and magnetism, which possibly enables opportunities for exotic phenomena and new spintronic devices. |
Tuesday, March 7, 2023 5:12PM - 5:24PM |
K55.00012: Strain effect on magnetocrystalline anisotropy of Fe2As from first principles Junehu Park, Andre Schleife There has been emerging interest in metallic antiferromagnets since the potential for electrical switching was shown for CuMnAs and Mn2Au. Magnetocrystalline anisotropy (MCA) is essential to understand spin dynamics and spin switching, and strain can be utilized to modify the anisotropy energy. We used first-principles density functional theory to compute the strain dependence of MCA for Fe2As, which has the same magnetic structure as CuMnAs. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K55.00013: Antiferromagnetic artificial neuron modeling of biological neural networks Hannah Bradley, Lily Quach, Steven Louis, Vasyl S Tyberkevych Replicating neural responses observed in biological systems using artificial neural networks has applications in both medicine and engineering. Here, we use an artificial neuron model based on antiferromagnetic (AFM) spin Hall oscillators [1] to model the biological withdrawal reflex responsible for the preservation of self from a harmful stimulus. The withdrawal reflex responds to sensory stimuli by flexing agonist muscles and relaxing the opposing antagonist muscles in the same limb [2]. We build an artificial neural network from AFM neurons that simulates the biological neural network responsible for this reflex. The unique features of AFM neurons, such as inhibition that stems from an effective AFM inertia, allow for the creation of biologically realistic neural network components, like the interneurons in the spinal cord. The effectiveness of AFM neuron modeling is proven by simulating various scenarios that define the withdrawal reflex, such as the reaction to a weak or strong stimulus and voluntary suppression of the reflex. |
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