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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Synthesis of high-density olivine LiFePO 4 from paleozoic siderite FeCO 3 and its electrochemical performance in lithium batteries

The lithium-ion cathode material olivine LiFePO 4 (LFP) has been synthesized for the first time from natural paleozoic iron carbonate (FeCO 3 ). The ferrous carbonate starting material consists of the mineral siderite at about 92 wt. % purity. Because FeCO 3 has divalent iron, the reaction with lithium dihydrogen phosphate (LiH 2 PO 4 ) provides a unique method to develop iron-(II) containing LFP in an inert atmosphere. Since siderite FeCO 3 is a common mineral that can be directly mined, it may, therefore, provide an inexpensive route for the production of LFP. After carbon-coating, the LFP yields a capacity in the range of 80–110 mAh g -1 LFP (in one chosen specimen sample), which is lower than commercially available LiFePO 4 (150–160 mAh g -1 LFP ). However, the tap density of LFP derived from siderite is noticeably high at 1.65 g cm -3 . The material is likely to be improved with powder purification, nanosized processing, and more complete carbon-coating coverage with increased optimization.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Porous FeCo Glassy Alloy as Bifunctional Support for High-Performance Zn-Air Battery

Zn-air battery (ZAB) is attracting increasing attention due to its high safety and performance. However, the practical application of ZAB relies heavily on developing durable support materials to replace conventional carbon supports which have unrecoverable corrosion issues, severely jeopardizing ZAB performance. Herein, a novel porous FeCo glassy alloy was developed as bifunctional catalytic support for ZAB. Specifically, the conducting skeleton of the porous glassy alloy was used to stabilize oxygen reduction cocatalysts, and more importantly, the FeCo served as the primary phase for oxygen evolution. To prove the concept of catalytic glassy alloy support, ultra-small Pd nanoparticles were anchored, as oxygen reduction active sites, on the porous FeCo (noted as Pd/FeCo) for ZAB. The Pd/FeCo exhibited a significantly improved electrocatalytic activity for oxygen reduction (a half-wave potential of 0.85 V) and oxygen evolution (a potential of 1.55 V to reach 10 mA cm –2 ) in the alkaline media. When used in the ZAB, the Pd/FeCo delivered an output power density of 117 mW cm –2 and outstanding cycling stability for over 200 h (400 cycles), surpassing the conventional carbon-supported Pt/C+IrO 2 catalysts. Such an integrated design of combining highly active components with porous architecture provides a new strategy to develop novel nanostructured electrocatalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCo by Materials Project

FeCo is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Fe is bonded in a body-centered cubic geometry to eight equivalent Co atoms. All Fe–Co bond lengths are 2.46 Å. Co is bonded in a body-centered cubic geometry to eight equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCo(PO4)2 by Materials Project

FeCo(PO4)2 crystallizes in the trigonal R3 space group. The structure is three-dimensional. there are three inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with six PO4 tetrahedra and a faceface with one CoO6 octahedra. There are three shorter (1.93 Å) and three longer (2.11 Å) Fe–O bond lengths. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with six PO4 tetrahedra and a faceface with one CoO6 octahedra. There are three shorter (1.93 Å) and three longer (2.10 Å) Fe–O bond lengths. In the third Fe3+ site, Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with six PO4 tetrahedra and a faceface with one CoO6 octahedra. There are three shorter (1.92 Å) and three longer (2.10 Å) Fe–O bond lengths. There are three inequivalent Co3+ sites. In the first Co3+ site, Co3+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with six PO4 tetrahedra, a faceface with one FeO6 octahedra, and a faceface with one CoO6 octahedra. There are three shorter (2.06 Å) and three longer (2.11 Å) Co–O bond lengths. In the second Co3+ site, Co3+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with six PO4 tetrahedra and a faceface with one CoO6 octahedra. There are three shorter (1.90 Å) and three longer (2.10 Å) Co–O bond lengths. In the third Co3+ site, Co3+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with six PO4 tetrahedra and faces with two FeO6 octahedra. All Co–O bond lengths are 2.08 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and corners with three CoO6 octahedra. The corner-sharing octahedra tilt angles range from 30–53°. There are a spread of P–O bond distances ranging from 1.52–1.57 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and corners with three CoO6 octahedra. The corner-sharing octahedra tilt angles range from 29–53°. There is two shorter (1.52 Å) and two longer (1.57 Å) P–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Co3+, and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Co3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Co3+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Co3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Co3+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCo(PO4)2 by Materials Project

FeCo(PO4)2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent CoO6 octahedra, corners with four PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Fe–O bond distances ranging from 1.95–2.16 Å. Co3+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with four equivalent FeO6 octahedra, corners with four PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Co–O bond distances ranging from 1.90–2.27 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CoO6 octahedra, corners with three equivalent FeO6 octahedra, and an edgeedge with one CoO6 octahedra. The corner-sharing octahedra tilt angles range from 39–56°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with three equivalent CoO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are a spread of P–O bond distances ranging from 1.51–1.59 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Fe3+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Co3+ and one P5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Co3+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe3+, one Co3+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Co3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th2(FeCo)5 by Materials Project

Th2(FeCo)5 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. there are two inequivalent Th sites. In the first Th site, Th is bonded in a 6-coordinate geometry to twelve Fe and six Co atoms. There are a spread of Th–Fe bond distances ranging from 3.20–3.23 Å. There are four shorter (2.84 Å) and two longer (2.93 Å) Th–Co bond lengths. In the second Th site, Th is bonded in a 6-coordinate geometry to eight Fe and ten Co atoms. All Th–Fe bond lengths are 3.18 Å. There are a spread of Th–Co bond distances ranging from 2.88–3.23 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to four equivalent Th, four Fe, and four equivalent Co atoms to form distorted FeTh4Fe4Co4 cuboctahedra that share corners with four equivalent CoTh4Fe4Co4 cuboctahedra, corners with twelve FeTh4Fe4Co4 cuboctahedra, edges with ten FeTh4Fe4Co4 cuboctahedra, and faces with ten FeTh4Fe4Co4 cuboctahedra. There are two shorter (2.53 Å) and two longer (2.54 Å) Fe–Fe bond lengths. All Fe–Co bond lengths are 2.45 Å. In the second Fe site, Fe is bonded to four Th, three Fe, and five Co atoms to form distorted FeTh4Fe3Co5 cuboctahedra that share corners with two equivalent CoTh4Fe4Co4 cuboctahedra, corners with fourteen FeTh4Fe4Co4 cuboctahedra, edges with two equivalent CoTh4Fe4Co4 cuboctahedra, edges with eight FeTh4Fe4Co4 cuboctahedra, faces with two equivalent CoTh4Fe4Co4 cuboctahedra, and faces with eight FeTh4Fe4Co4 cuboctahedra. There are one shorter (2.50 Å) and one longer (2.52 Å) Fe–Fe bond lengths. There are a spread of Fe–Co bond distances ranging from 2.42–2.51 Å. In the third Fe site, Fe is bonded to four Th, three Fe, and five Co atoms to form distorted FeTh4Fe3Co5 cuboctahedra that share corners with two equivalent CoTh4Fe4Co4 cuboctahedra, corners with fourteen FeTh4Fe4Co4 cuboctahedra, edges with two equivalent CoTh4Fe4Co4 cuboctahedra, edges with eight FeTh4Fe4Co4 cuboctahedra, faces with two equivalent CoTh4Fe4Co4 cuboctahedra, and faces with eight FeTh4Fe4Co4 cuboctahedra. There are three shorter (2.45 Å) and two longer (2.46 Å) Fe–Co bond lengths. There are three inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to three Th, four Fe, and two equivalent Co atoms. Both Co–Co bond lengths are 2.49 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to three Th and six Fe atoms. In the third Co site, Co is bonded to four equivalent Th, four Fe, and four equivalent Co atoms to form distorted CoTh4Fe4Co4 cuboctahedra that share corners with four equivalent CoTh4Fe4Co4 cuboctahedra, corners with twelve FeTh4Fe4Co4 cuboctahedra, edges with two equivalent CoTh4Fe4Co4 cuboctahedra, edges with eight FeTh4Fe3Co5 cuboctahedra, faces with two equivalent CoTh4Fe4Co4 cuboctahedra, and faces with eight FeTh4Fe3Co5 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCo(BiO3)2 by Materials Project

FeCo(BiO3)2 crystallizes in the tetragonal P4mm space group. The structure is three-dimensional. Fe3+ is bonded in a 5-coordinate geometry to five O2- atoms. There is one shorter (1.82 Å) and four longer (2.04 Å) Fe–O bond length. Co3+ is bonded in a 5-coordinate geometry to five O2- atoms. There is one shorter (1.76 Å) and four longer (2.03 Å) Co–O bond length. There are two inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.30 Å) and four longer (2.84 Å) Bi–O bond lengths. In the second Bi3+ site, Bi3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.30 Å) and four longer (2.85 Å) Bi–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Co3+ and four equivalent Bi3+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Fe3+ and four equivalent Bi3+ atoms. In the third O2- site, O2- is bonded to two equivalent Co3+ and two equivalent Bi3+ atoms to form a mixture of distorted corner and edge-sharing OCo2Bi2 tetrahedra. In the fourth O2- site, O2- is bonded to two equivalent Fe3+ and two equivalent Bi3+ atoms to form a mixture of distorted corner and edge-sharing OFe2Bi2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCo(NiS2)4 by Materials Project

FeCo(NiS2)4 is Spinel-derived structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Fe3+ is bonded to four equivalent S2- atoms to form FeS4 tetrahedra that share corners with twelve equivalent NiS6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Fe–S bond lengths are 2.11 Å. Co3+ is bonded to four equivalent S2- atoms to form CoS4 tetrahedra that share corners with twelve equivalent NiS6 octahedra. The corner-sharing octahedral tilt angles are 57°. All Co–S bond lengths are 2.13 Å. Ni+2.50+ is bonded to six S2- atoms to form NiS6 octahedra that share corners with three equivalent FeS4 tetrahedra, corners with three equivalent CoS4 tetrahedra, and edges with six equivalent NiS6 octahedra. There are three shorter (2.29 Å) and three longer (2.30 Å) Ni–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Co3+ and three equivalent Ni+2.50+ atoms. In the second S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Fe3+ and three equivalent Ni+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCo by Materials Project

FeCo is Tungsten-derived structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Fe is bonded in a distorted body-centered cubic geometry to four equivalent Fe and four equivalent Co atoms. All Fe–Fe bond lengths are 2.47 Å. All Fe–Co bond lengths are 2.46 Å. Co is bonded in a distorted body-centered cubic geometry to four equivalent Fe and four equivalent Co atoms. All Co–Co bond lengths are 2.47 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZrGa6(FeCo)3 by Materials Project

ZrGa6(FeCo)3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Zr is bonded to four Fe, six Co, and eight Ga atoms to form distorted ZrGa8Fe4Co6 hexagonal bipyramids that share corners with six equivalent ZrGa8Fe4Co6 hexagonal bipyramids, edges with four CoZr2Ga6Fe3Co cuboctahedra, faces with eight CoZr2Ga6Fe3Co cuboctahedra, faces with twelve FeGa6Co4 cuboctahedra, and faces with two equivalent ZrGa8Fe4Co6 hexagonal bipyramids. There are two shorter (3.23 Å) and two longer (3.25 Å) Zr–Fe bond lengths. There are a spread of Zr–Co bond distances ranging from 3.19–3.25 Å. There are a spread of Zr–Ga bond distances ranging from 2.80–2.94 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to four Co and six Ga atoms to form distorted FeGa6Co4 cuboctahedra that share corners with four equivalent CoZr2Ga6Fe3Co cuboctahedra, corners with ten FeGa6Co4 cuboctahedra, edges with two equivalent CoZr2Ga6Fe3Co cuboctahedra, edges with four FeZr2Ga6Fe2Co2 cuboctahedra, faces with four CoZr2Ga6Fe3Co cuboctahedra, and faces with four equivalent ZrGa8Fe4Co6 hexagonal bipyramids. There are two shorter (2.48 Å) and two longer (2.49 Å) Fe–Co bond lengths. There are a spread of Fe–Ga bond distances ranging from 2.50–2.60 Å. In the second Fe site, Fe is bonded to two equivalent Zr, two equivalent Fe, two equivalent Co, and six Ga atoms to form distorted FeZr2Ga6Fe2Co2 cuboctahedra that share corners with six CoZr2Ga6Fe3Co cuboctahedra, corners with ten FeGa6Co4 cuboctahedra, edges with two equivalent FeGa6Co4 cuboctahedra, edges with four CoZr2Ga6Fe3Co cuboctahedra, faces with two equivalent FeZr2Ga6Fe2Co2 cuboctahedra, faces with six CoZr2Ga6Fe3Co cuboctahedra, and faces with four equivalent ZrGa8Fe4Co6 hexagonal bipyramids. Both Fe–Fe bond lengths are 2.49 Å. Both Fe–Co bond lengths are 2.46 Å. There are a spread of Fe–Ga bond distances ranging from 2.53–2.60 Å. In the third Fe site, Fe is bonded to two equivalent Zr, two equivalent Fe, two equivalent Co, and six Ga atoms to form distorted FeZr2Ga6Fe2Co2 cuboctahedra that share corners with six CoZr2Ga6Fe3Co cuboctahedra, corners with ten FeGa6Co4 cuboctahedra, edges with two equivalent FeGa6Co4 cuboctahedra, edges with four CoZr2Ga6Fe3Co cuboctahedra, faces with two equivalent FeZr2Ga6Fe2Co2 cuboctahedra, faces with six CoZr2Ga6Fe3Co cuboctahedra, and faces with four equivalent ZrGa8Fe4Co6 hexagonal bipyramids. Both Fe–Co bond lengths are 2.48 Å. There are a spread of Fe–Ga bond distances ranging from 2.53–2.60 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to two equivalent Zr, three Fe, one Co, and six Ga atoms to form distorted CoZr2Ga6Fe3Co cuboctahedra that share corners with six FeGa6Co4 cuboctahedra, corners with eight CoZr2Ga6Fe3Co cuboctahedra, edges with three FeGa6Co4 cuboctahedra, edges with four CoZr2Ga6Fe3Co cuboctahedra, an edgeedge with one ZrGa8Fe4Co6 hexagonal bipyramid, faces with three CoZr2Ga6Fe3Co cuboctahedra, faces with five FeGa6Co4 cuboctahedra, and faces with three equivalent ZrGa8Fe4Co6 hexagonal bipyramids. The Co–Co bond length is 2.54 Å. There are a spread of Co–Ga bond distances ranging from 2.53–2.62 Å. In the second Co site, Co is bonded to two equivalent Zr, two equivalent Fe, two equivalent Co, and six Ga atoms to form distorted CoZr2Ga6Fe2Co2 cuboctahedra that share corners with four FeZr2Ga6Fe2Co2 cuboctahedra, corners with eight CoZr2Ga6Fe3Co cuboctahedra, edges with two equivalent CoZr2Ga6Fe3Co cuboctahedra, edges with four FeZr2Ga6Fe2Co2 cuboctahedra, edges with two equivalent ZrGa8Fe4Co6 hexagonal bipyramids, faces with four equivalent CoZr2Ga6Fe3Co cuboctahedra, faces with six FeGa6Co4 cuboctahedra, and faces with two equivalent ZrGa8Fe4Co6 hexagonal bipyramids. There are a spread of Co–Ga bond distances ranging from 2.50–2.55 Å. There are three inequivalent Ga sites. In the first Ga site, Ga is bonded in a 8-coordinate geometry to two equivalent Zr, three Fe, and three Co atoms. In the second Ga site, Ga is bonded in a 8-coordinate geometry to one Zr, three Fe, three Co, and one Ga atom. The Ga–Ga bond length is 2.74 Å. In the third Ga site, Ga is bonded in a 10-coordinate geometry to one Zr, three Fe, and three Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Manipulating electron redistribution to achieve electronic pyroelectricity in molecular [FeCo] crystals

Pyroelectricity plays a crucial role in modern sensors and energy conversion devices. However, obtaining materials with large and nearly constant pyroelectric coefficients over a wide temperature range for practical uses remains a formidable challenge. Attempting to discover a solution to this obstacle, we combined molecular design of labile electronic structure with the crystal engineering of the molecular orientation in lattice. This combination results in electronic pyroelectricity of purely molecular origin. Here, we report a polar crystal of an [FeCo] dinuclear complex exhibiting a peculiar pyroelectric behavior (a substantial sharp pyroelectric current peak and an unusual continuous pyroelectric current at higher temperatures) which is caused by a combination of Fe spin crossover (SCO) and electron transfer between the high-spin Fe ion and redox-active ligand, namely valence tautomerism (VT). As a result, temperature dependence of the pyroelectric behavior reported here is opposite from conventional ferroelectrics and originates from a transition between three distinct electronic structures. The obtained pyroelectric coefficient is comparable to that of polyvinylidene difluoride at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tailoring light-induced charge transfer and intersystem crossing in FeCO using time-dependent spin–orbit configuration interaction

Real-time (RT) electronic structure methods provide a natural framework for describing light–matter interactions in arbitrary time-dependent electromagnetic fields (EMF). Optically induced excited state transitions are of particular interest, which require tuned EMF to drive population transfer to and from the specific state(s) of interest. Intersystem crossing, or spin-flip, may be driven through shaped EMF or laser pulses. These transitions can result in long-lived “spin-trapped” excited states, which are especially useful for materials requiring charge separation or protracted excited state lifetimes. Time-dependent configuration interaction (TDCI) is unique among RT methods in that it may be implemented in a basis of eigenstates, allowing for rapid propagation of the time-dependent Schrödinger equation. The recent spin–orbit TDCI (TD-SOCI) enables a real-time description of spin-flip dynamics in an arbitrary EMF and, therefore, provides an ideal framework for rational pulse design. The present study explores the mechanism of multiple spin-flip pathways for a model transition metal complex, FeCO, using shaped pulses designed to drive controlled intersystem crossing and charge transfer. These results show that extremely tunable excited state dynamics can be achieved by considering the dipole transition matrix elements between the states of interest.

Chemistry↗
DOE OSTI2024

Effects of Post-sintering Annealing on (NdLa)-(FeCo)-B Magnets

A common limitation of La substitutions into (Nd, La) 2 Fe 14 B magnets is the reduction of the anisotropy field (H a ), which decreases magnet coercivity (H cj ). In this study, adding a small amount of Pr-Cu to a La-containing neo magnet may modify the grain boundary (GB), which can help recover a fraction of the degraded H cj . An optimal GB modification requires a carefully designed post-sinter heat treatment, which is the focus of this work on characterizing the effects of multi-step post-sintering annealing on the evolutions of microstructure and magnetic properties. We find that Nd and Cu concentrations at GBs and triple junctions (TJs) increase when the annealing temperatures are lowered. Annealing temperatures of 580°C and 480°C (near rare-earth-rich eutectic temperatures) enabled the development of a thick and continuous GB phase, which helps to magnetically decouple the grains, and, thus, enhance H cj . For the alloy with 25% Nd replaced by La, and with the addition of 7.5 wt.% of Pr 68 Cu 32 as GB modifier, the optimized multi-step post-sinter annealing improved the H cj from 4.8 kOe to 9 kOe.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Additive roles of antiferromagnetically coupled elements in the magnetic proximity effect in the GdFeCo/Pt system

Abstract Interfacial magnetic interactions between different elements are the origin of various spin-transport phenomena in multi-elemental magnetic systems. We investigate the coupling between the magnetic moments of the rare-earth, transition-metal, and heavy-metal elements across the interface in a GdFeCo/Pt thin film, an archetype system to investigate ferrimagnetic spintronics. The Pt magnetic moments induced by the antiferromagnetically aligned FeCo and Gd moments are measured using element-resolved x-ray measurements. It is revealed that the proximity-induced Pt magnetic moments are always aligned parallel to the FeCo magnetic moments, even below the ferrimagnetic compensation temperature where FeCo has a smaller moment than Gd. This is understood by a theoretical model showing distinct effects of the rare-earth Gd 4 f and transition-metal FeCo 3 d magnetic moments on the Pt electronic states. In particular, the Gd and FeCo work in-phase to align the Pt moment in the same direction, despite their antiferromagnetic configuration. The unexpected additive roles of the two antiferromagnetically coupled elements exemplify the importance of detailed interactions among the constituent elements in understanding magnetic and spintronic properties of thin film systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗