Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session Y41: Magnetic Materials, Not OxidesFocus
|
Hide Abstracts |
Sponsoring Units: GMAG DMP Chair: Patrick Quarterman, National Institute of Standards and Technology Room: BCEC 209 |
(Author Not Attending)
|
Y41.00001: Exploring the Magnetic Properties of the Iron-Nitrogen System Todd Monson, Tyler Stevens, Stan Atcitty, Baolong Zheng, Yizhang Zhou, Enrique Lavernia The magnetic properties of the iron-nitrogen system have only been explored on a very limited basis. Theoretical predictions of the magnetic behavior of the different phases of iron nitride are limited and experimental data is quite sparse. By employing several different techniques which include solution based nanoparticle nitridation, electrochemical methods, and metathesis based reactions we have synthesized several different phases of iron nitride: FeN, Fe2N, Fe3N, Fe4N, and Fe24N10. Additionally, we have demonstrated a path for consolidating raw powders of iron nitride into bulk material, enabling additional characterization and application in macroscopic devices. Our difficulties and successes in synthesizing and processing these different phases of iron nitride will be described. Additionally, the magnetic properties of these seldom explored iron-nitrogen compounds will be summarized. |
Friday, March 8, 2019 11:27AM - 11:39AM |
Y41.00002: Mn-based Heusler Compounds with Low Magnetization Wenyong Zhnag, Balamurugan Balasubramanian, Rabindra Pahari, Ahsan Ullah, Shah Valloppilly, Ralph Skomski, David Sellmyer Heusler compounds with small or zero magnetization are of interest for spintronics applications, because they cause little or no fringing fields and may exhibit ultrafast dynamics and high spin polarization [1-3]. We find virtually zero room-temperature magnetizations in stoichiometric Ru2MnSn and Pt2MnGa Heusler alloys fabricated by rapid quenching from the melt. X-ray diffraction patterns show the formation of a L21 structures with a = 6.22 Å and a tetragonal structure with a = 4.02 Å and c = 7.24 Å in Ru2MnSn and Pt2MnGa, respectively. Both systems show nearly linear M(H) curves for intermediate field strengths of several T, and the slopes dM/dH are used to characterize the spin structure. In Pt2MnGa, which shows a helical spins structure with an ordering temperature of about 350 K [4], dM/dH increases with decreasing spiral wave vector q. The complex spin structures of Ru2MnSn and Pt2MnGa are used to explain the electron-transport properties of the alloys. |
Friday, March 8, 2019 11:39AM - 11:51AM |
Y41.00003: ABSTRACT WITHDRAWN
|
Friday, March 8, 2019 11:51AM - 12:03PM |
Y41.00004: Disorder and electron correlation effects in the ground state of Ni-Co-Mn-Sn alloys with Heusler structures Aki Pulkkinen, Bernardo Barbiellini, Johannes Nokelainen, Vladimir Sokolovskiy, Vasiliy D. Buchelnikov, Mikhail Zagrebin, Katariina Pussi, Erkki Lahderanta, Alexander Granovsky
|
Friday, March 8, 2019 12:03PM - 12:15PM |
Y41.00005: ABSTRACT WITHDRAWN
|
Friday, March 8, 2019 12:15PM - 12:27PM |
Y41.00006: Tuning the magnetic properties of NiBr2 with cobalt doping Hasitha Suriya Arachchige, Binod Rai, Ganesh Pokharel, Andrew May, Adam Aczel, Travis J Williams, Matthias D Frontzek, Cristian Batista, David George Mandrus, Andrew D Christianson The compound NiBr2 crystallizes in the trigonal space group R-3m. Below TN= 44 K, NiBr2 exhibits antiferromagnetic order characterized by antiferromagnetically stacked sheets of ferromagnetically aligned Ni spins. A transition to a helical magnetic structure occurs below TIC=22.8 K with a propagation vector of at 4.2 K. Here we use neutron diffraction to study the tuning of the magnetic properties with cobalt substitution in single crystals for several compositions of Ni1-xCoxBr2, where x = 0, 0.2, 0.25, 0.3, and 0.45. Our measurements show that the TN decreases with doping while changes in TIC are more subtle. The neutron scattering studies further reveal that the 6 incommensurate spots in the parent compound give way to a ring of magnetic scattering reminiscent of that observed previously for Ni0.92Zn0.08Br2. |
Friday, March 8, 2019 12:27PM - 12:39PM |
Y41.00007: Eu-Si nanowires formation on Si(100) studied by scanning tunneling microscopy and spectroscopy Aaron Wang, Te-Yu Chien By depositing Eu onto a cleaned Si(100) surface at 400 oC, patterned nanowires are formed and visualized by scanning tunneling microscopy(STM). The nanowires are measured to be ~1.5 nm in diameter, ~1 Å in height and hundreds of nm or more in length. The spacing between the nanowires are found to be mostly 2.2 nm, 2.8 nm and 3.4nm, i.e. with 0.6 nm increment. Interestingly, the topography images taken at positive and negative bias show single-wire and double-wire morphologies, respectively. Same observations are made in the dI/dV mapping with positive and negative bias. Furthermore, dI/dV spectra taken at the double-wire features (found while scanning at negative bias) exhibit peak-valley features in the valence band - a peak at -3.2 V and valley at -3.4 V. Similar peak-valley dI/dV spectra were reported for the Pt/Si nanowires, which showed signs of strong Rashba spin splitting [1]. Further studies are underway in determining the possibility of strong Rashba effect in this Eu/Si nanowire systems. |
Friday, March 8, 2019 12:39PM - 12:51PM |
Y41.00008: Effect of Bi addition on the magnetic and structural properties of chemically synthesized Fe-Pt-Ni alloy Vimal Deepchand, Frank M Abel, Vasileios Tzitzios, George C Hadjipanayis L10 FePt has been chosen as the ideal candidate for heat assisted magnetic recording media due to its high magnetocrystalline anisotropy of ~70 Merg/cc, and thermal stability down to 3 nm [1]. Producing L10 alloys with high thermal stability, while reducing the Curie temperature is critical for the development of heat assisted magnetic recording media, and has led to the exploration of third element doping into the L10 FePt [2]. In this work, we studied the effect of bismuth addition on chemically synthesized FePt1-xNix alloys, with x=0.2 – 0.4. The as-made particles showed an fcc structure, but after annealing at 700oC for 30 minutes a transformation to the L10 phase occurred. The addition of Bi appears to enhance the ordering of the L10 alloy relative to the ternary Fe-Pt-Ni but leads to the formation of a secondary phase. Thermomagnetic measurements show a reduction in Curie temperature compared to the Fe-Pt-Ni ternary alloy in the x=0.3 case, which suggests that Bi enters the structure of the L10 alloy. Current efforts are focused on varying the Bi content to optimize the magnetic and structural properties of Fe-Pt-Ni. |
Friday, March 8, 2019 12:51PM - 1:03PM |
Y41.00009: Concentration tuned tetragonal strain in alloys: application to magnetic anisotropy of FeNi1-xCox Alex Wysocki, Manh Cuong Nguyen, Andrey Postnikov, Vladimir Antropov We explore an opportunity to induce and control tetragonal distortion in materials using the ideas of Bain transformation path for multiatomic systems with body– and face-centered symmetries. The concept is illustrated in the case of FeNi1-xCox magnetic alloy formed by substitutional doping of the L10 FeNi magnet with Co. Using electronic structure calculations we demonstrate that the tetragonal strain in this system can be controlled by concentration and it reaches maximum around x = 0.5. This finding is then applied to create a large magnetocrystalline anisotropy in FeNi1-xCox system. We demonstrate that this anisotropy can be significantly improved by delicate tuning the tetragonal distortion, electronic concentration and chemical anisotropy. We discuss possible experimental ways to create such magnet. |
Friday, March 8, 2019 1:03PM - 1:15PM |
Y41.00010: Magnetic and Structural Properties of Melt-Spun Co-Ge Ribbons Onur Tosun, Frank M Abel, Balamurugan Balasubramanian, Ralph Skomski, David Sellmyer, George C Hadjipanayis The Co-Ge materials is a key subsystem of Heusler alloys and have attracted much interest because they play an important role in the field of integrated circuits [1, 2]. In this work, we have investigated the magnetic and structural properties of Co-Ge melt-spun ribbons in an attempt to understand better the behavior of our Co2Ge nanoparticles prepared by the cluster-beam deposition technique. Melt-spun ribbons with different compositions and different wheel speeds were prepared. Our data showed that small variations in the Co content and wheel speed lead to different structures and magnetic properties. The ribbons with 65% Co composition are ferromagnetic at room temperature with Curie temperatures larger than 800 K in contrast to previous reports that claimed to be ferromagnetic at cryogenic temperatures [3]. The contradiction with the literature could be attributed to the difference in grain size in the ribbons and can explain the effect of size on the magnetic properties of our nanoparticles. |
Friday, March 8, 2019 1:15PM - 1:27PM |
Y41.00011: Studying static and dynamic magnetic properties of individual 22.6-nm superparamagnetic nanoparticles using diamond magnetic microscopy Abdelghani Laraoui, Ilja Fescenko, Janis Smits, Nazanin Mosavian, Pauli Kehayias, Andrey Jarmola, Victor Acosta Nitrogen-vacancy Centers (NVC) in diamond are presently being investigated as sensitive probes of the magnetic properties of materials at the nanometer scale. This is facilitated by their unique properties, including the sub-ms spin coherence time and superb photostability at room temperature. We developed a new strategy based on NVC for high throughput, high spatio-temporal resolution characterization of individual magnetic nanoparticles (MNPs) for biomedical imaging. We doped a diamond chip with a near-surface layer of NVC and used it to perform wide-field microscopy by optically detecting the NV magnetic resonance frequencies. We measured the static and dynamic magnetic properties of individual 22.6-nm superparamagnetic nanoparticles and correlated them with their morphology determined from atomic force microscopy. The static magnetic images reveal magnetic dipole field patterns from small clusters as well as weaker signatures (~4 uT) from individual MNPs. The dynamic properties, dominated by Néel relaxation, show a variation of relaxation times, explained by size variation (~5%). This study provides first step to understand the effect of size and surface structure on MNP magnetic properties. |
Friday, March 8, 2019 1:27PM - 1:39PM |
Y41.00012: Quantitative size-structure-magnetic property relationships in thoroughly-characterized metallic Ni nanoparticle assemblies Joseph Batley, My Nguyen, Ishita Kamboj, Eray S. Aydil, Chris Leighton Recent advances in colloidal synthesis and other approaches have realized nanoparticles(NPs) with controlled structure, size, functionalization, and self-assembly. In magnetism, the focus on hard ferromagnetic(FM) NPs and oxides has left relatively little research on metallic soft FM NPs. Here, Ni NPs have been synthesized via injection of a Ni-oleylamine(OAm) complex into 200°C trioctylphosphine(TOP). Size control was obtained by varying TOP/OAm ratio, reaction time, and by differential centrifugation. Characterization was performed with X-ray diffraction, transmission electron microscopy, Raman and Fourier-transform infrared spectroscopy, and SQUID magnetometry. Polycrystalline FCC NPs are obtained, with mean diameter, <D>, tunable from 4—22 nm, and dispersion, σ/<D> = 10-30%. Superparamagnetic blocking can thus be tuned between 15 and >300 K. Size distributions and inter-particle interactions are explicitly accounted for, quantitatively reconciling differences between the true mean blocking temperature, <TB>, and the zero field cooled magnetization peak. The resulting <TB>vs.<D> yields an effective anisotropy surprisingly close to that of bulk Ni. Reduced saturation magnetization is observed, but is consistent with a NixPy or spin-canted shell ~1 nm thick. |
Friday, March 8, 2019 1:39PM - 1:51PM |
Y41.00013: Magneto-Controlled Biocatalytic Cascades with Logically Processed Input Signals – Substrate Channeling versus Free Diffusion Yaroslav Filipov, Andrey Zakharchenko, Sergiy Minko, Evgeny Katz Magnetic nanoparticles (MNPs) functionalized with various enzymes (amyloglucosidase, glucose oxidase and horseradish peroxidase) were used to perform biocatalytic cascades in two different states, solute suspension or aggregated, produced in the absence or presence of an external magnetic field. The biocatalytic reactions proceeded through bulk solution diffusion of intermediate substrates or substrate channeling, when the systems were dispersed or aggregated, respectively. The both pathways have shown very similar kinetics, unless the intermediate substrate was consumed by an additional biocatalytic process called “filter” for brevity. In the presence of the “filter” process, the diffusional process in the bulk solution was significantly inhibited, while the process based on the substrate channeling was still active. The systems were switched reversibly between the inhibited dispersed state and the active aggregated state by removing and applying the external magnetic field, respectively. The signal-controlled biocatalytic cascades were considered as Boolean logic circuits with the inputs consisting of biomolecules and the magnetic filed on-off. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700