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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Tb(Ni2P)2 by Materials Project

Tb(Ni2P)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Tb is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.81 Å) and four longer (2.86 Å) Tb–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.31 Å) and one longer (2.32 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Tb and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(BIr)4 by Materials Project

Tb(IrB)4 is alpha Pu-derived structured and crystallizes in the tetragonal P4_2/n space group. The structure is three-dimensional. Tb is bonded in a 4-coordinate geometry to four equivalent B atoms. All Tb–B bond lengths are 2.90 Å. Ir is bonded in a 4-coordinate geometry to four equivalent B atoms. There are a spread of Ir–B bond distances ranging from 2.10–2.18 Å. B is bonded in a 6-coordinate geometry to one Tb, four equivalent Ir, and one B atom. The B–B bond length is 1.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Glassy correlated state induced by disorder in the frustrated antiferromagnet Tb 2 Zr 2 O 7

Here, we study the low-temperature thermomagnetic properties of the polycrystalline material Tb 2 Zr 2 O 7 through ac susceptibility and specific heat measurements. This zirconate displays a defect-fluorite structure in which the magnetic Tb 3+ and nonmagnetic Zr 4+ cations sit randomly on the same metal sublattice. No long-range magnetic order is found down to 100 mK, although dominant antiferromagnetic interactions are observed and the spins remain dynamic down to the lowest temperatures investigated. We observed a frequency-dependent peak around 2.5 K which is well described by many models of a canonical spin-glass transition. In-field specific heat measurements and the recovered entropy of the system R ln(4) suggest a two doublets ground state separated by 7 K. Comparisons to the pyrochlores Tb 2 Ti 2 O 7 and Tb 2 Hf 2 O 7 reinforce the collective spin-glass-type behavior and the opening for discussions of an exotic Coulomb phase in this material.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electrically tuned hyperfine spectrum in neutral Tb( II )(Cp iPr5 ) 2 single-molecule magnet

Molecular spin qubits with long spin coherence time as well as non-invasive operation methods on such qubits are in high demand. It was shown that both molecular electronic and nuclear spin levels can be used as qubits. In solid state systems with dopants, an electric field was shown to effectively change the spacing between the nuclear spin qubit levels when the electron spin density is high at the nucleus of the dopant. Inspired by such solid-state systems, we propose that divalent lanthanide (Ln) complexes with an unusual electronic configuration of Ln 2+ have a strong interaction between the Ln nuclear spin and the electronic degrees of freedom, which renders electrical tuning of the interaction. Furthermore, as an example, we study electronic structure and hyperfine interaction of the 159 Tb nucleus in a neutral Tb(II)(Cp iPr5 ) 2 single-molecule magnet (SMM), which exhibits unusually long magnetization relaxation time, using the complete active space self-consistent field (CASSCF) method with spin–orbit interaction included within the restricted active space state interaction (RASSI). Our calculations show that the low-energy states arise from 4f 8 (6s,5d z 2 ) 1 , 4f 8 (5d x 2 -y 2 ) 1 , and 4f 8 (5d xy ) 1 configurations. We compute the hyperfine interaction parameters and the electronic–nuclear spectrum within our multiconfigurational approach. We find that the hyperfine interaction is about one order of magnitude greater than that for Tb(III)Pc 2 SMMs. This stems from the strong Fermi contact interaction between the Tb nuclear spin and the electron spin density at the nucleus that originates from the occupation of the (6s,5d) orbitals. We also uncover that the response of the Fermi contact term to electric field results in electrical tuning of the electronic–nuclear level separations. This hyperfine Stark effect may be useful for applications of molecular nuclear spins for quantum computing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Local structure study on magnetostrictive material Tb 1–x Dy x Fe 2

Tb 1–x Dy x Fe 2 system has attracted more research interest due to the large magnetostrictive effect. The crystal structures and physical properties have been well studied, but research studies on their local structures are still rare. As such, in this work, the local structure of Tb 1–x Dy x Fe 2 samples was studied using the pair distribution function and x-ray absorption spectroscopy techniques. The results demonstrate that the system owns the same local crystal symmetry with its average structure in the ferromagnetic phase, and the crystal lattice of the system is more ordered with increasing Dy content, indicating that the Dy-rich tetragonal phase is more stable than the Tb-rich rhombohedral phase. The different roles of metallic bonds in affecting the crystal lattice are presented. The weak Fe 1 –Fe 2 bonds influenced by the local environment such as local stress from randomly distributed nanodomains could originate the anomalies in the lattice, resulting in the more ordered and stable Dy-rich phase than the Tb-rich phase.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Short-range magnetic correlations in quasicrystalline i -Tb-Cd

Here, we report on elastic and inelastic neutron scattering from single-grain isotopically enriched samples to elucidate the local magnetic correlations between Tb 3+ moments in quasicrystalline i -Tb-Cd. The inelastic neutron scattering measurements of the crystalline electric field excitations demonstrated that the Tb 3+ moments are directed primarily along the local fivefold axes of the Tsai-type cluster as was found for the TbCd 6 approximant phase. Based on the inelastic measurements, we consider a simple Ising-type model for the moment configurations on a single Tb 3+ icosahedron and enumerate the lowest energy moment configurations. We then calculate the diffuse scattering from these configurations and compare with the experimental magnetic diffuse scattering measurements to identify the most likely single cluster moment configurations and find reasonable agreement between the broad features observed in our scattering simulations. We further use a heuristic glass model as well as large-scale Monte-Carlo simulations of a multicluster model to consider the role of higher-order (longer-range) intercluster correlations for magnetic frustration and the magnetic scattering.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Tb(AlSi)2 by Materials Project

TbAl2Si2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Tb is bonded to six equivalent Si atoms to form distorted TbSi6 octahedra that share corners with twelve equivalent AlSi4 tetrahedra, edges with six equivalent TbSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Tb–Si bond lengths are 2.98 Å. Al is bonded to four equivalent Si atoms to form distorted AlSi4 tetrahedra that share corners with six equivalent TbSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent TbSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–55°. There are three shorter (2.51 Å) and one longer (2.53 Å) Al–Si bond lengths. Si is bonded to three equivalent Tb and four equivalent Al atoms to form a mixture of distorted edge and corner-sharing SiTb3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(MnGe)2 by Materials Project

TbMn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tb is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Tb–Ge bond lengths are 3.08 Å. Mn is bonded to four equivalent Ge atoms to form a mixture of corner and edge-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Tb, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.60 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(AlCl4)3 by Materials Project

Tb(AlCl4)3 crystallizes in the trigonal P3_112 space group. The structure is one-dimensional and consists of one Tb(AlCl4)3 ribbon oriented in the (0, 0, 1) direction. Tb3+ is bonded in a 8-coordinate geometry to eight Cl1- atoms. There are a spread of Tb–Cl bond distances ranging from 2.75–2.93 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Cl1- atoms. There are two shorter (2.16 Å) and two longer (2.17 Å) Al–Cl bond lengths. In the second Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Cl1- atoms. There are a spread of Al–Cl bond distances ranging from 2.10–2.24 Å. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Tb3+ and one Al3+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Al3+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Al3+ atom. In the fourth Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Tb3+ and one Al3+ atom. In the fifth Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Tb3+ and one Al3+ atom. In the sixth Cl1- site, Cl1- is bonded in an L-shaped geometry to one Tb3+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(AlGe)2 by Materials Project

TbAl2Ge2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Tb is bonded to six equivalent Ge atoms to form distorted TbGe6 octahedra that share corners with twelve equivalent AlGe4 tetrahedra, edges with six equivalent TbGe6 octahedra, and edges with six equivalent AlGe4 tetrahedra. All Tb–Ge bond lengths are 3.01 Å. Al is bonded to four equivalent Ge atoms to form distorted AlGe4 tetrahedra that share corners with six equivalent TbGe6 octahedra, corners with six equivalent AlGe4 tetrahedra, edges with three equivalent TbGe6 octahedra, and edges with three equivalent AlGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–55°. There are three shorter (2.56 Å) and one longer (2.57 Å) Al–Ge bond lengths. Ge is bonded to three equivalent Tb and four equivalent Al atoms to form a mixture of distorted edge and corner-sharing GeTb3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(PO3)3 by Materials Project

Tb(PO3)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded to six O2- atoms to form TbO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Tb–O bond distances ranging from 2.25–2.33 Å. In the second Tb3+ site, Tb3+ is bonded to six O2- atoms to form TbO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Tb–O bond distances ranging from 2.25–2.32 Å. There are seven inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TbO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 29–43°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TbO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 11–19°. There is two shorter (1.50 Å) and two longer (1.60 Å) P–O bond length. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TbO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–31°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TbO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 18°. There is two shorter (1.50 Å) and two longer (1.61 Å) P–O bond length. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TbO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–42°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TbO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 10–32°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the seventh P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TbO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 26°. There is two shorter (1.50 Å) and two longer (1.60 Å) P–O bond length. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to one Tb3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a linear geometry to one Tb3+ and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tb3+ and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the seventeenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb(PO)2 by Materials Project

Tb(PO)2 crystallizes in the tetragonal I4_1/amd space group. The structure is zero-dimensional and consists of eight Tb(PO)2 clusters. Tb3+ is bonded in a linear geometry to two equivalent O2- atoms. Both Tb–O bond lengths are 2.24 Å. P+0.50+ is bonded in a single-bond geometry to one O2- atom. The P–O bond length is 1.58 Å. O2- is bonded in a water-like geometry to one Tb3+ and one P+0.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Pure- and mixed-gas transport properties of a microporous Tröger's Base polymer (PIM-EA-TB)

Polymers of intrinsic microporosity (PIMs) offer tantalizing combinations of high selectivity and permeability in initial gas permeation measurements. Here, we report characterization of pure- and mixed-gas permeation properties of a thick (~80 μm) PIM consisting of Tröger's Base (TB) and Ethanoanthracene (EA) films. The effects of feed pressure and temperature on pure-gas permeabilities of CH 4 , N 2 , O 2 , H 2 , and CO 2 were investigated. The physical aging behavior of the thick film was tracked via pure-gas O 2 , N 2 , and CH 4 permeability at 35 °C. Gas permeability decreased noticeably and selectivity increased as aging time increased. Particular attention was given to mixed-gas measurements of CO 2 and CH 4 (50/50) permeabilities at 35 °C and fugacities ranging from 2 to 18 atm to explore whether the rigid, bridged, bicyclic TB and EA units could resist CO 2 -induced plasticization. These results are presented along with pure-gas CO 2 and CH 4 results for membrane samples aged at different times. PIM-EA-TB aged for ~24 h did not show signs of plasticization across the fugacity range considered. Furthermore, dual-mode competitive sorption presumably caused the CO 2 /CH 4 mixed-gas selectivity to be slightly higher than its corresponding pure-gas selectivity. However, as aging time increased, aged films underwent progressively more rapid and extensive CO 2 -induced plasticization with increasing fugacity, suggesting a systematic relationship between physical aging and plasticization in PIMs. Consequently, physical aging caused less improvement in mixed-gas CO 2 /CH 4 selectivity than it did in pure-gas selectivity, due mainly to plasticization effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Evolution of Physical Properties of RE 3 Ni 5 Al 19 Family (RE = Y, Nd, Sm, Gd, Tb, Dy, Ho, and Er)

In this study, single crystals of RE 3 Ni 5 Al 19 series (RE = Y, Nd, Sm, Gd, Tb, Dy, Ho, and Er) are grown using the Al self-flux method. The crystal structure is examined by both single crystal and powder X-ray diffraction. Physical properties are studied for the first time for RE 3 Ni 5 Al 19 (RE = Y, Nd, Gd, Tb, Dy, Ho, and Er) by means of magnetic susceptibility, electrical resistivity, and heat capacity measurements. Complex magnetic behaviors, with up to three transitions present for RE = Sm, Gd, Tb, and Dy, are revealed. Y 3 Ni 5 Al 19 is found to be a nonmagnetic nonsuperconducting metal (above T = 1.8 K) with weak electron–phonon coupling strength.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Quaternary i-MAX Phases (Mo 2/3 RE 1/3 ) 2 AlC (RE: Dy, Tb, Er): Experimental Characterization and First-Principles Insights into their Fundamental Properties

Rare earth (RE)-based materials have unique electronic, magnetic, and optical properties, leading to the recent discovery of atomically layered solids with the chemical formula (M' 2/3 RE 1/3 ) 2 AlC, which have since garnered significant attention in the scientific community. This study aims to synthesize, characterize, and investigate the structural and thermal stability of the RE i-MAX phases. We prepared i-MAX phases using molybdenum (Mo) as M′ and RE elements as Dy, Tb, and Er, namely (Mo 2/3 Dy 1/3 ) 2 AlC, (Mo 2/3 Tb 1/3 ) 2 AlC, and (Mo 2/3 Er 1/3 ) 2 AlC. Structural characterization through x-ray diffraction (XRD) and Raman spectroscopy confirms the formation of the RE-based i-MAX phase, along with the presence of minor impurity phases in the alloys. Thermogravimetric analysis (TGA) conducted up to 1000°C under ambient conditions reveals that the i-MAX phases remain thermally stable up to approximately 450°C, beyond which oxidation leads to a noticeable weight gain in all samples. Differential scanning calorimetry (DSC) measurements during heating and cooling cycles show endothermic and exothermic peaks for (Mo 2/3 Dy 1/3 ) 2 AlC i-MAX in the 410–420°C range, indicating a temperature-induced minor atomic arrangement. In contrast, these peaks are absent in the Tb- and Er-based i-MAX phases. These findings offer valuable insights into the thermal behavior and stability of these i-MAX phases under thermal stress, contributing to a deeper understanding of their unique properties. Furthermore, first-principles density functional theory (DFT) calculations were performed to investigate the electronic and optical properties of the i-MAX phases. The results reveal their metallic nature, with pronounced contributions from Mo and RE elements near the Fermi level and within the conduction band.

Rare earth↗
DOE OSTI2025

Energy migration and scintillation kinetics in compositionally complex (Gd 1/4 Y 1/4 Tb 1/4 Lu 1/4 ) 3 Al 5 O 12 :Ce single crystal scintillator

It is well-established that compositional tuning through binary admixture can improve scintillation performance in several materials systems, including Ce-activated garnets. Although recent work on ternary or quaternary cation admixture shows promise, the impact of this increased compositional complexity on thermal stability and carrier-defect dynamics has not been addressed. Here, we investigate a compositionally complex garnet, (Gd 1/4 Y 1/4 Tb 1/4 Lu 1/4 ) 3 Al 5 O 12 :Ce (GYTLAG), grown by the Czochralski method using temperature-dependent photoluminescence (PL), PL decay, and thermoluminescence (TL). PL and PL decay measurements support a thermally activated Tb 3+ -Ce 3+ energy transfer, where Tb 3+ emission dominates below 60 K, but Ce 3+ emission increases from 20-300 K. Thermal quenching of Ce 3+ emission occurs around T 50 = 508 K, with an activation energy of 0.6 eV. TL and wavelength-resolved TL spectra from 20–500 K show that GYTLAG contains similar trap groups to LuAG but with a broader distribution of glow peaks below room temperature, possibly caused by quaternary cation mixing. A combination of dose dependence, partial cleaning and initial rise, and glow curve fitting to a first order continuous Gaussian distribution model are used to understand the contribution of electronic point defects to scintillation decay and afterglow at room temperature. Furthermore, these results inform how increased compositional complexity influences recombination dynamics in garnet scintillators.

Compositionally complex↗
DOE OSTI2023

XANES analysis of phosphate glasses melted with Tb 4 O 7 and SnO: evaluating the impact of valence states on structural, thermal, and luminescent properties

Barium phosphate glasses were prepared with 0.5 mol% Tb 4 O 7 added alongside SnO up to 5 mol% with the purpose of evaluating the resulting terbium and tin oxidation states and their impact on glass structural, thermal, and luminescent properties. In this work, following material synthesis by melt-quenching, the composition-structure–property investigation was pursued encompassing measurements by X-ray diffraction (XRD), X-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy, differential scanning calorimetry (DSC), dilatometry, and photoluminescence (PL) spectroscopy. While XRD confirmed the amorphous nature of the glasses, results from XANES indicated that terbium occurs as terbium(III) with a predisposition for tin to exist as tin(IV) which decreased at high SnO content. The structural as well as the thermal properties appeared to be mostly impacted by the presence of tin(IV). Specifically, glass depolymerization was indicated to be induced by Sn 4+ ions, and their concentration was observed to correlate with glass transition and softening temperatures. On the other hand, the tin(II) remnants were observed to exert an impact on the luminescent properties shifting light emission from the green towards the blue-green (cyan). It is indicated that Tb 4 O 7 reacting to produce Tb 2 O 3 supports the oxidation of tin(II) to tin(IV) which in turn dominates the physical properties. However, this was somewhat circumvented at the highest SnO content wherein tin(IV) appeared to be lower.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Role of element-specific damping in ultrafast, helicity-independent, all-optical switching dynamics in amorphous (Gd,Tb)Co thin films

Ultrafast control of the magnetization in ps timescales by fs laser pulses offers an attractive avenue for applications such as fast magnetic devices for logic and memory. However, ultrafast helicity-independent all-optical switching (HI-AOS) of the magnetization has thus far only been observed in Gd-based, ferrimagnetic amorphous (a-) rare earth-transition metal (a-RE-TM) systems, and a comprehensive understanding of the reversal mechanism remains elusive. Here, we report HI-AOS in ferrimagnetic a-Gd 22-x Tb x Co 78 thin films, from x=0 to 18, and elucidate the role of Gd in HI-AOS in a-RE-TM alloys and multilayers. Increasing Tb content results in increasing perpendicular magnetic anisotropy and coercivity, without modifying magnetization density, and slower remagnetization rates and higher critical fluences for switching but still shows picosecond HI-AOS. Simulations of the atomistic spin dynamics based on the two-temperature model reproduce these results qualitatively and predict that the lower damping on the RE sublattice arising from the small spin-orbit coupling of Gd (with L=0) is instrumental for the faster dynamics and lower critical fluences of the Gd-rich alloys. Annealing a-Gd 10 Tb 12 Co 78 leads to slower dynamics which we argue is due to an increase in damping. These simulations strongly indicate that accounting for element-specific damping is crucial in understanding HI-AOS phenomena. The results suggest that engineering the element-specific damping of materials can open up new classes of materials that exhibit low-energy, ultrafast HI-AOS.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗