Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session X45: Magnetic Anisotropy: Hard and Soft MaterialsFocus
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Sponsoring Units: GMAG Chair: Scooter Johnson, U.S. Naval Research Laboratory Room: 706 |
Friday, March 6, 2020 11:15AM - 11:27AM |
X45.00001: First-principles calculations on the surfaces and interfaces of SmFe12 Tomoharu Shiozawa, Yuta Ainai, Yasutomi Tatetsu, Yoshihiro Gohda Nd-Fe-B sintered magnets are currently used in a wide range in industry. However, it is seriously problematic that the coercivity of Nd-Fe-B sintered magnets significantly decreases at high temperatures. In contrast, a new magnetic compound SmFe12 has a higher magnetic anisotropy than Nd2Fe14B which is the main phase of Nd-Fe-B sintered magnets. Therefore, SmFe12-based magnets can be expected as a preferable alternative of existent magnets. The performance of magnets is strongly influenced by microstructural interfaces. However, there are few studies about interfaces including SmFe12. |
Friday, March 6, 2020 11:27AM - 11:39AM |
X45.00002: Additive manufacturing of PPS bonded NdFeB magnets to design a Halbach array for polarized neutron reflectivity experiments Tej Lamichhane Additive manufacturing (AM) is a layer by layer material printing technology which is found to be very useful in permanent magnet (PM) manufacturing. In bonded PM, the mechanical strength and the loading volume fraction of magnetic materials can be increased by mechanical extrusion of optimally magnetic particle loaded polymer composites. AM process reduces the price of magnet production by reducing the waste of magnetic materials via net-shaped printing and avoiding the cost of expensive complex molding tools needed for small scale industrial production. AM printed isotropic polyphenylene sulfide (PPS) bonded Nd-Fe-B magnets were used to design a cylindrical Halbach array for polarized neutron reflectivity measurements. We will discuss in detail about the challenges associated in developing the prototype Halbach ring magnet and validate the concept of variable magnetic contrast in neutron measurements. |
Friday, March 6, 2020 11:39AM - 11:51AM |
X45.00003: First-principles Study on Crystalline Nd-Fe alloys as Candidate Structures for Grain-Boundaries in Nd-Fe-B Sintered Magnets Yuta Ainai, Yasutomi Tatetsu, Asako Terasawa, Yoshihiro Gohda Due to technological progress in industry, the coercivity enhancement of Nd-Fe-B sintered magnets at high temperatures is highly demanded. It has been identified that the grain-boundaries (GBs) are known as Nd-Fe alloys with fcc diffraction patterns. However, the detailed atomic arrangement on the atomic scale is still unclear. Therefore, in this study, we investigated Nd-rich alloys with Fe as a candidate structures for GBs. |
Friday, March 6, 2020 11:51AM - 12:27PM |
X45.00004: Low-Dimensional Hard Magnetic Materials Invited Speaker: J Liu Ferromagnetism is a size-dependent physical phenomenon. Although the size dependence has been studied in theory for decades, nanoscale ferromagnetic materials especially hard magnetic nanostructures and materials with controllable size and shape are not available till recently. We have worked at bottom-up approaches to preparation of low-dimensional hard magnetic materials including nanoparticles and nanowires/nanorods. By adopting newly developed “salt-matrix annealing”, “surfactant-assisted milling” and improved chemical solution techniques, we have successfully synthesized monodisperse hard magnetic FePt and SmCo nanoparticles as well as FeCo, CoNi, CoCx and Co based nanowires/nanorods. These first-ever-available nanoscale ferromagnets display various hard and soft magnetic properties at room temperature which are found to be strongly size and shape dependent. A systematic study on size dependent Curie temperature of the L10 structured FePt ferromagnetic nanoparticles with size from 2 to 15 nanometers reveals the finite size effect in the tiny ferromagnets. In case of the Co nanowires with controlled diameter and length, coercivity up to the theoretical limit has been achieved that renewed our understanding of the Brown’s Paradox. The ferromagnetic nanocrystals can be used as building blocks for advanced bulk and thin film magnets, and can be also applied in biomedicine and ferrofluid technologies. |
Friday, March 6, 2020 12:27PM - 12:39PM |
X45.00005: High-throughput search for rare-earth free permanent magnets Alena Vishina, Olga Vekilova, Heike Herper, Olle Eriksson High performance permanent magnets are needed for a large number of applications, such as electric motors, wind mills. At the same time most high performance magnets contain rare-earth (RE) materials which makes them expensive. |
Friday, March 6, 2020 12:39PM - 12:51PM |
X45.00006: Development of magnetic hardness in melt-spun Mn50Bi50-xMx alloys (M = Mg, In, Sn, Sb, Bi) subjected to magnetic-field annealing Alexander Gabay, George C Hadjipanayis The theoretical maximum energy product (BH)m of the MnBi compound, 20 MGOe, perfectly fits the "gap" between the inexpensive hard ferrites and the supply-critical rare-earth magnets. Decades of R&D efforts focused on consolidation of fine MnBi single crystals could only produce MnBi magnets exhibiting (BH)m of 5–8 MGOe. A different approach relying on a melt-spinning, followed by compaction and magnetic-field annealing avoids the highly reactive single crystals, but it does not develop coercivity Hc in the binary MnBi alloys. Here, we report how alloying with M = Mg, In, Sn and Sb affects the phases, the texture and the hard magnetic properties of field-annealed magnets prepared from the melt-spun Mn50Bi50-xMx alloys. Sn delays the formation of the MnBi phase while further decreases the already low Hc. 1.5 at.% In decreases the solidus temperature and slightly increases the Hc. In melt-spun alloys modified with 1.5 at.% Sb, a transient metastable phase ensures a submicron size of MnBi grains and leads to a Hc >7 kOe, but suppression of the texture limits the (BH)m to 5.4 MGOe. Alloying with Mg increases the Hc without undermining the texture; a breakthrough (BH)m of 9.8 MGOe was realized in the Mn50Bi47Mg3 magnet. |
Friday, March 6, 2020 12:51PM - 1:03PM |
X45.00007: Tuning of spin reorientation temperature of SmFeO3: Role of exchange interaction between 4f & 3d electrons AZAM KHAN, Anju Ahlawat, Srinibas satapathy, Ak Karnal Emergent technologies based on spintronics demand the unprecedented control on magnetic anisotropy. Here we present the control on magnetic anisotropy of SmFeO3 by the means of Tm3+doping at Sm3+site. A series of nano particles of Sm1-xTmxFeO3 (X=0, 0.3, 0.5, 0.7, 1) orthoferrite have been synthesized by sol-gel auto-combustion method and phase purity was confirmed by the X-ray diffraction pattern. The crystallographic information obtained from Rietveld refinement and Raman spectroscopy confirmed the changes in oxygen octahedra with the change in doping percentage of Tm3+ ion in SmFeO3. Temperature dependent dc magnetization measurement implies the tuning of spin reorientation temperature from 480 K to 80 K as a function of Tm3+ ion doping concentration. The room temperature magnetic isotherm confirms the canted antiferromagnetic character of nano particles. Sm0.7Tm0.3FeO3 shows the spin reorientation at room temperature which might be used in room temperature spintronics devices. |
Friday, March 6, 2020 1:03PM - 1:15PM |
X45.00008: Self-biased nanocrystalline barium hexaferrite thick films formed by aerosol deposition for microwave devices Scooter Johnson, Dong-Soo Park, Sanghoon Shin, Syed B Qadri, Pavel Kabos, kevin coakley, Edward P Gorzkowski High-frequency devices utilizing magnetic materials such as barium hexaferrite (BaFe12O19, BaM) are critical for many electronics. One promising route to forming these materials is aerosol deposition (AD), a process that creates thick 95% dense films by room-temperature impact consolidation*. AD utilizes high-velocity impact to fracture and mechanically and chemically bonds solid particles together. |
Friday, March 6, 2020 1:15PM - 1:27PM |
X45.00009: Investigation of fabrication method of L10-FeCo multilayer film Hisaaki Ito, Takuya Miyashita, Takuya Kumagai, Toshio Miyamachi, Fumio Komori, Tomoyuki Koganezawa, Takuo Ohkochi, Masato Kotsugi The L10-type FeCo ordered phase exhibits large magnetic anisotropy, large magnetic moment, and high Curie temperature. Since L10-FeCo does not contain rare-earth elements, it is a potential candidate as a high-performance magnetic material [1]. On the other hand, the L10-FeCo system is at a non-equilibrium state, and its fabrication has been a challenge so far [2]. To overcome the problem, we inserted periodic buffer layers between the FeCo layers to maintain the L10 (fcc) structure [3]. For establishing the fabrication method of L10-FeCo, we here investigated the growth temperature (Ts) dependence of (7 ML-FeCo/3 ML-Ni buffer)3 films fabricated by pulsed laser deposition. |
Friday, March 6, 2020 1:27PM - 1:39PM |
X45.00010: Influence of W thickness on Perpendicular Magneto-crystalline Anisotropy of Pt/Co/W(111) Superlattices Huynh Thi Ho, Sanghoon Kim, Sonny H. Rhim, Soon Cheol Hong Tri-layer superlattice with reflection asymmetry in the spirit of Rashba effect has been |
Friday, March 6, 2020 1:39PM - 1:51PM |
X45.00011: An efficient model for modelling Barkhausen noise in PMA thin films Audun Skaugen, Lasse Laurson The motion of domain walls in thin films with perpendicular magnetic |
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