Advanced Magnetic Materials for Energy and Power Conversion Applications: Developments in Emerging Permanent Magnets
Sponsored by: TMS Functional Materials Division, TMS: Magnetic Materials Committee
Program Organizers: Richard Beddingfield, GE; Daniel Salazar, BCMaterials; Alex Leary, NASA Glenn Research Center; Huseyin Ucar, California Polytechnic University,Pomona; Yongmei Jin, Michigan Technological University; Arcady Zhukov, University of the Basque Country
Thursday 8:30 AM
March 18, 2021
Room: RM 25
Location: TMS2021 Virtual
Session Chair: Yongmei Jin, Michigan Technological University; Zachary Morgan, Oak Ridge National Laboratory
8:30 AM
Atomic Cooperation in Enhancing Magnetism: (Fe, Cu)-doped CeCo5: Durga Paudyal1; Renu Choudhary1; 1Ames Laboratory
Employing electronic-structure theory, we identify the weakly localized nature of cobalt in CeCo5, which causes high uniaxial magnetic anisotropy of ~ 10 MJ/m3. In contrast, substituted Cu delocalizes the Co’s 3d-states, resulting in lower anisotropy. Calculations show that 10% Cu can stabilize 20% Fe replaced for the Co, which significantly enhances magnetic moment in the Ce (Co, Fe, Cu)5. This prediction is in good agreement with a single-crystal experiment in which the best optimal composition was identified to be 15% of Fe and 12% Cu. The competitive Co sites preferred by Cu and Fe, a unique electronic-structure including exchange and crystal field splitting, and rigid-band shift variation are borne by 3d states of Co, Fe, and Cu around the Fermi level, all play an essential role in tuning the magnetic properties.This work is supported by CMI, an Energy Innovation Hub, funded by the USDOE, Office of EERE, AMO.
8:50 AM
Computational Modeling of Fracture in Sm-Co Magnet: Ikenna Nlebedim1; Xubo Liu1; Baozhi Cui1; Jun Cui1; 1Ames Laboratory
Samarium-cobalt (Sm-Co) magnets are the strongest magnets for high temperature (>300˚C) applications but their intrinsic brittle feature makes them susceptible to chipping and fracturing during magnet fabrication and device assembly. We will present full field micromechanics modeling targeted at improving the fracture toughness by correlating microstructure and fracture behavior. Crack initialization and growth were treated using a phase field method. Our simulated microstructure models include Sm-Co with single grain size distribution, oxide particle doped Sm-Co magnet, and laminated Sm-Co with alternating fine and coarse size layers. It was found that intragranular fracture behavior remains dominant, irrespective of the microstructure type. We will discuss the effects of grain refinement, especially due to additives, on fracture behavior. We will also show the roles of interfaces in complex laminated microstructures, including how each microstructural feature influences fracture toughness. Finally, our presentation will reveal possible routes to enhancing fracture toughness while considering magnetic performance.
9:10 AM
Effects of Lattice Distortions on Magnetic Properties of Fe16N2: First-principles Study: Yusuke Asari1; Tomohiro Tabata1; Shinya Tamura1; Matachiro Komuro1; Shohei Terada1; 1Hitachi, Ltd.
Fe16N2 phase is a promising magnetic material due to its high saturation magnetic flux density, but there have been no consensus among researchers regarding the mechanisms of the magnetism. Now we investigated the mechanisms of the magnetism of Fe16N2 by means of the first principles density functional theory within the generalized gradient approximation from a viewpoint of effects of change in the lattice volume on the saturation magnetic flux density. Our calculation shows that the saturation magnetic flux density is dependent on the unitcell volume. The change in the unitcell volume causes the change in the magnetic moments at the iron sites, because the magnetic moments depend on the interatomic distance between irons.
9:30 AM
Heterogeneous Sm-Co Sintered Magnets with Enhanced Mechanical Properties: Baozhi Cui1; Xubo Liu1; Gaoyuan Ouyang1; Cajetan Nlebedim1; Jun Cui1; 1Ames Laboratory
SmCo5 and Sm2Co17 type sintered magnets have been widely used in telecommunication, sensors, and energy conversion, especially, at elevated temperatures of 200 - 550 oC. Though Sm-Co sintered magnets possess excellent magnetic properties, they are brittle. The brittleness limits their applications and also leads to magnet production loss up to 20-30%. Improving flexural strength or fracture toughness of Sm-Co magnets is of great scientific and technical significance. This work studied the formation of novel heterogeneous grain microstructures and their strengthening mechanisms in Sm-Co sintered magnets. Flexural strength or fracture toughness values of Sm2(CoFeCuZr)17 sintered magnets were enhanced by about 50-75 % while excellent magnetic properties were maintained. The results showed that engineering grain microstructures, without changing the chemical compositions of magnets and heat treatment procedures, was an effective way to achieve an unprecedented combination of superior mechanical and magnetic properties in Sm-Co sintered magnets.
9:50 AM Invited
MnBi Thin Film Micromagnets with Tunable Anisotropy for High Temperature Applications: M. Villanueva1; E. H. Sánchez2; P. Pedraz1; P. Olleros1; P. Perna1; P. S. Normile2; C. Navío1; J. Camarero1; Jose De Toro2; A. Bollero1; 1IMDEA Nanoscience, Madrid, Spain; 2IRICA & Applied Physics Dept, University of Castilla-La Mancha, Spain
The low temperature phase (LTP) of MnBi, with hexagonal crystal structure, is receiving increasing attention due to its high magnetic anisotropy and Curie temperature, as well as to the outstanding increase in coercivity with temperature. LTP-MnBi microcrystals of different size have been prepared as (quasi-) hexagonal islands by RF-magnetron sputtering of composite targets. AFM shows crater-like shapes, which allows for a facile study of the domain configuration as a function of thickness. The microcrystals, grown at 300 K, exhibit perpendicular anisotropy with coercive fields (up to 10.7 kOe) dependent on the substrate temperature during deposition. Higher deposition temperatures (475 K) yield rods lying on the substrate displaying in-plane anisotropy with a remarkable coercivity of 20 kOe at 400 K. Thus, the magnetic anisotropy can be tuned without applied external fields. Finally, ongoing efforts on the dispersion of high saturation magnetization FeCo nanoparticles in the above material will be discussed.
10:20 AM
Role of Fe in Stabilizing Ce(Co, Fe, Cu)5 and Enhancing Its Magnetic Properties: Matthew Kramer1; Oleana Palasyuk1; Tae-Hoon Kim1; Lin Zhou1; Sergey Budko1; Paul Canfield1; Andriy Palasyuk1; 1Ames Laboratory
The Ce(Co1-xFex)4.4Cu0.6 (0 ≤ x ≤ 0.19) shows potential as a ‘gap’ magnet and provides insight into novel composition/structure relationship to coercivity. The X-ray, SEM and TEM analyses confirm this is a RETM5-type single-phase material at high temperature (RE – rare earth, and TM - transition metals Co, Cu and Fe). After heat treatment, these compounds forms dense arrays of basal plane 2:7-type stacking faults. With increasing Fe, these stacking faults segregate into various closely related 1:5 and 1:2 structural units related to RE2TM7 and RE5TM19 precipitates. The measured anisotropy energy density, Curie temperature, magnetization, remanance and coercivity all increase with increasing Fe up to x = 0.186, near the solubility limit of Fe. Fe and Cu initially stabilize CaCu5 type-structure, but with increasing Fe, the structure locally competes 2:7-like structural arrangements forming planar defects. These defects, together with the increasing anisotropy field, are crucial to greatly improved magnetic properties.
10:40 AM
Evaluation of Medium-entropy FexCoyNiz Alloys as Precursors for FeCoNi-based High Entropy Magnetic Alloys: Alex Paul1; Tanjore Jayaraman1; 1University of Michigan-Dearborn
High-entropy magnetic alloys present an excellent combination of functional and structural properties that broadens the space for developing high-performance magnetic alloys for several energy conversion applications. We evaluated the suitability of several FexCoyNiz alloy compositions, whose configurational entropy (ΔSconfig) is higher than ~9 J/mol K, as a precursor for FeCoNi-based high entropy magnetic alloys. We evaluated and compared the structure and magnetic properties of mechanically alloyed FexCoyNiz over a range of temperatures—structure by x-ray diffraction and electron microscopy, and magnetic properties by vibrating sample magnetometry. Most compositions comprised the γ phase and the rest γ + α phase. The magnetic saturation (Ms) was as high as ~150 Am2/kg and coercivity (Hc) as high as ~5 kA/m. The magnetic anisotropy (K) was on the order of 10^6 J/m3. The Ms and Hc increased at sub-ambient temperatures. With the increase in thermal-treatment temperature, the MS and Hc increased and decreased, respectively.
11:00 AM
Substitutional and Interstitial Doping in 1-5 and Its Derivative Structures for the Development of Hard Magnetic Properties: A First Principles Study: Huseyin Ucar1; Durga Paudyal2; 1California Polytechnic University, Pomona; 2Ames Laboratory
We investigate the changes in the electronic structure at the transition metal sites of the RE-TM5 structure (RE=Rare Earth, TM=Transition Metal) while doping the interstitial sites with nitrogen. LaCo5 compound is taken as the baseline compound owing to its respectable intrinsic magnetic properties such as magneto-crystalline anisotropy energy (MAE) of ≈ 5 meV/fu due to the contributions from the cobalt network. Addition of nitrogen is shown to reduce the local spin moments of the nearest TM due to the hybridization present between N-2p states and the TM-3d states. More importantly, we show how a planar anisotropy becomes a strong uniaxial anisotropy after the addition of nitrogen into LaCo2Fe3 and LaCo2Mn3, and linked this transformation to the band structure changes after nitrogenation. Similar doping mechanisms can also be performed in 2-12 or 2-17 type intermetallics that yield enhanced hard magnetic properties due to these structures being derived from the 1-5 structure.