Browse
Submit Data
Databases
API
Help

Dataset Information

15 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

High Blocking Temperature of Magnetization and Giant Coercivity in the Azafullerene Tb2 @C79 N with a Single-Electron Terbium-Terbium Bond.

ABSTRACT: The azafullerene Tb2 @C79 N is found to be a single-molecule magnet with a high 100-s blocking temperature of magnetization of 24?K and large coercivity. Tb magnetic moments with an easy-axis single-ion magnetic anisotropy are strongly coupled by the unpaired spin of the single-electron Tb-Tb bond. Relaxation of magnetization in Tb2 @C79 N below 15?K proceeds via quantum tunneling of magnetization with the characteristic time ?QTM =16?462±1230?s. At higher temperature, relaxation follows the Orbach mechanism with a barrier of 757±4?K, corresponding to the excited states, in which one of the Tb spins is flipped.

SUBMITTER: Velkos G

PROVIDER: S-EPMC6519270 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

High Blocking Temperature of Magnetization and Giant Coercivity in the Azafullerene Tb2 @C79 N with a Single-Electron Terbium-Terbium Bond.

Velkos Georgios G Krylov Denis S DS Kirkpatrick Kyle K Spree Lukas L Dubrovin Vasilii V Büchner Bernd B Avdoshenko Stanislav M SM Bezmelnitsyn Valeriy V Davis Sean S Faust Paul P Duchamp James J Dorn Harry C HC Popov Alexey A AA

Angewandte Chemie (International ed. in English) 20190327 18

The azafullerene Tb2 @C79 N is found to be a single-molecule magnet with a high 100-s blocking temperature of magnetization of 24 K and large coercivity. Tb magnetic moments with an easy-axis single-ion magnetic anisotropy are strongly coupled by the unpaired spin of the single-electron Tb-Tb bond. Relaxation of magnetization in Tb2 @C79 N below 15 K proceeds via quantum tunneling of magnetization with the characteristic time τQTM =16 462±12 ...[more]

PMID: 30786125

Similar Datasets

Giant exchange coupling and field-induced slow relaxation of magnetization in Gd2@C79N with a single-electron Gd-Gd bond.

Project description:Magnetic properties of the azafullerene Gd2@C79N are studied by SQUID magnetometry. The effective exchange coupling constant jGd,e between the Gd spins and the spin of unpaired electron residing on the single-electron Gd-Gd bond is determined to be 170 ± 10 cm-1. Low temperature AC measurements revealed field-induced millisecond-long relaxation of magnetization.

| S-EPMC5885278 | biostudies-literature

Giant coercivity and high magnetic blocking temperatures for N23- radical-bridged dilanthanide complexes upon ligand dissociation.

Project description:Increasing the operating temperatures of single-molecule magnets-molecules that can retain magnetic polarization in the absence of an applied field-has potential implications toward information storage and computing, and may also inform the development of new bulk magnets. Progress toward these goals relies upon the development of synthetic chemistry enabling enhancement of the thermal barrier to reversal of the magnetic moment, while suppressing alternative relaxation processes. Herein, we show that pairing the axial magnetic anisotropy enforced by tetramethylcyclopentadienyl (CpMe4H) capping ligands with strong magnetic exchange coupling provided by an N23- radical bridging ligand results in a series of dilanthanide complexes exhibiting exceptionally large magnetic hysteresis loops that persist to high temperatures. Significantly, reducing the coordination number of the metal centers appears to increase axial magnetic anisotropy, giving rise to larger magnetic relaxation barriers and 100-s magnetic blocking temperatures of up to 20?K, as observed for the complex [K(crypt-222)][(CpMe4H2Tb)2(?-[Formula: see text])].

| S-EPMC5732206 | biostudies-literature

Transformation of Amorphous Terbium Metal-Organic Framework on Terbium Oxide TbOx(111) Thin Film on Pt(111) Substrate: Structure of TbxOy Film.

Project description:The present study is focused on the synthesis and structural properties of amorphous terbium metal-organic framework thin film (TbMOF-TF) and its transformation to terbium oxide by pyrolysis at 450 °C in the air. The crystalline (cTbMOF) and amorphous (aTbMOF) films were prepared by solvothermal synthesis using different amounts (0.4 and 0.7 mmol) of the modulator (sodium acetate), respectively. The powders were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM). The varied chemical composition of the surface of TbMOFs and TbxOy was investigated by X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aTbMOF had been fully transformed to a Tb4O7 phase with a cubic crystal structure at 450 °C. The amorphous aTbMOF-TF film was prepared by dropping a colloidal solution of amorphous precursor nanocrystals on the SiO2/Si substrates covered with Pt as an interlayer. XPS confirmed the presence of Tb in two states, Tb3+ and Tb4+. The amorphous film has a rough, porous microstructure and is composed of large clusters of worm-like particles, while terbium oxide film consists of fine crystallites of cubic fluorite cF-TbOx, c-Tb4O7, and c-Tb2O3 phases. The surface topography was investigated by a combination of confocal (CM) and atomic force microscopy (AFM). The amorphous film is porous and rough, which is contrast to the crystalline terbium oxide film.

| S-EPMC9412416 | biostudies-literature

Penta-terbium lithium tris-tannide, Tb(5)LiSn(3).

Project description:The new ternary phase penta-terbium lithium tris-tannide, Tb(5)LiSn(3), crystallizes in the hexa-gonal Hf(5)CuSn(3) structure type, which is a 'filled' version of the binary RE(5)Sn(3) phases (Mn(5)Si(3)-type) (RE is rare earth). The asymmetric unit contains two Tb sites (site symmetries 3.2 and m2m), one Li site (site symmetry [Formula: see text].m) and one Sn site (site symmetry m2m). The 14-vertex Frank-Kasper polyhedra are typical for Li and Tb atoms. The environment of the Sn atom is a pseudo-Frank-Kasper polyhedron with a coordination number of 13 for the tin atom. One of the Tb atoms is enclosed in a 17-vertex polyhedron. The metallic type of bonding was indicated by an analysis of the inter-atomic distances.

| S-EPMC3246906 | biostudies-other

High coercivity SmCo5 synthesized with assistance of colloidal SiO2.

Project description:SmCo5 is one of the most promising candidates for achieving a hard magnet with a high coercivity. Usually, composition, morphology, and size determine the coercivity of a magnet, however, it is challenging to synthesize phase pure SmCo5 with optimal size and high coercivity. In this paper, we report on the successful synthesis of phase pure SmCo5 with spherical/prolate spheroids shape. Size control is obtained by utilizing colloidal SiO2 as a template preventing aggregation and growth of the precursor. The amount of SiO2 nanoparticles (NPs) in the precursor tunes the average particle size (APS) of the synthesized SmCo5 with particle dimension from 740 to 504 nm. As-prepared pure SmCo5 fine powder obtained from using 2 ml SiO2 suspension possesses an APS of 625 nm and exhibits an excellent coercivity of 2986 kA m-1 (37.5 kOe) without alignment of the particles prior to magnetisation measurements. Comparing with a reference sample prepared without adding any SiO2 NPs, an enhancement of 35% of the coercivity was achieved. The improvement is due to phase purity, stable single-domain (SSD) size, and shape anisotropy originating from the prolate spheroid particles.

| S-EPMC7907374 | biostudies-literature

A Simple Analytical Model for Magnetization and Coercivity of Hard/Soft Nanocomposite Magnets.

Project description:We present a simple analytical model to estimate the magnetization (σ s) and intrinsic coercivity (H ci) of a hard/soft nanocomposite magnet using the mass fraction. Previously proposed models are based on the volume fraction of the hard phase of the composite. However, it is difficult to measure the volume of the hard or soft phase material of a composite. We synthesized Sm2Co7/Fe-Co, MnAl/Fe-Co, MnBi/Fe-Co, and BaFe12O19/Fe-Co composites for characterization of their σ s and H ci. The experimental results are in good agreement with the present model. Therefore, this analytical model can be extended to predict the maximum energy product (BH)max of hard/soft composite.

| S-EPMC5504001 | biostudies-other

Highly efficient self-powered perovskite photodiode with an electron-blocking hole-transport NiOx layer.

Project description:Hybrid organic-inorganic perovskite materials provide noteworthy compact systems that could offer ground-breaking architectures for dynamic operations and advanced engineering in high-performance energy-harvesting optoelectronic devices. Here, we demonstrate a highly effective self-powered perovskite-based photodiode with an electron-blocking hole-transport layer (NiOx). A high value of responsivity (R = 360 mA W-1) with good detectivity (D = 2.1 × 1011 Jones) and external quantum efficiency (EQE = 76.5%) is achieved due to the excellent interface quality and suppression of the dark current at zero bias voltage owing to the NiOx layer, providing outcomes one order of magnitude higher than values currently in the literature. Meanwhile, the value of R is progressively increased to 428 mA W-1 with D = 3.6 × 1011 Jones and EQE = 77% at a bias voltage of - 1.0 V. With a diode model, we also attained a high value of the built-in potential with the NiOx layer, which is a direct signature of the improvement of the charge-selecting characteristics of the NiOx layer. We also observed fast rise and decay times of approximately 0.9 and 1.8 ms, respectively, at zero bias voltage. Hence, these astonishing results based on the perovskite active layer together with the charge-selective NiOx layer provide a platform on which to realise high-performance self-powered photodiode as well as energy-harvesting devices in the field of optoelectronics.

| S-EPMC7794468 | biostudies-literature

Single-shot all-optical switching of magnetization in Tb/Co multilayer-based electrodes.

Project description:Ever since the first observation of all-optical switching of magnetization in the ferrimagnetic alloy GdFeCo using femtosecond laser pulses, there has been significant interest in exploiting this process for data-recording applications. In particular, the ultrafast speed of the magnetic reversal can enable the writing speeds associated with magnetic memory devices to be potentially pushed towards THz frequencies. This work reports the development of perpendicular magnetic tunnel junctions incorporating a stack of Tb/Co nanolayers whose magnetization can be all-optically controlled via helicity-independent single-shot switching. Toggling of the magnetization of the Tb/Co electrode was achieved using either 60 femtosecond-long or 5 picosecond-long laser pulses, with incident fluences down to 3.5 mJ/cm2, for Co-rich compositions of the stack either in isolation or coupled to a CoFeB-electrode/MgO-barrier tunnel-junction stack. Successful switching of the CoFeB-[Tb/Co] electrodes was obtained even after annealing at 250?°C. After integration of the [Tb/Co]-based electrodes within perpendicular magnetic tunnel junctions yielded a maximum tunneling magnetoresistance signal of 41% and RxA value of 150 ??m2 with current-in-plane measurements and ratios between 28% and 38% in nanopatterned pillars. These results represent a breakthrough for the development of perpendicular magnetic tunnel junctions controllable using single laser pulses, and offer a technologically-viable path towards the realization of hybrid spintronic-photonic systems featuring THz switching speeds.

| S-EPMC7089968 | biostudies-literature

Coercivity Mechanism of (Nd0.8Ce0.2)2.4Fe12Co?B Ribbons with Ferromagnetic Grain Boundary Phase.

Project description:Understanding the coercivity mechanism has had a substantial impact on developing economically more attractive RE-based (RE = rare earth) permanent materials because of price volatility of key RE metals (i.e., Nd and Dy) in recent years. In this work, we investigated the microstructure and magnetic properties of melt-spun (Nd0.8Ce0.2)2.4Fe12Co?B ribbons and annealed samples at 773 K for 15 min with 1 Tesla (T) magnetic field to better understand the coercivity mechanism. We found hard magnetic grains were surrounded by thin and continuous layers along the grain boundaries (GBs) with a high concentration of ferromagnetic elements (Fe + Co >74 at%). The obvious positive peak in the ?M plot and the interaction domain structure observed by Lorentz magnetic microscopy indicate that there is strong exchange coupling interaction through the ferromagnetic GB phase between hard magnetic grains. The annealing in an applied magnetic field of 1 T increases the remanence by enhancing the exchange coupling interaction, leading to a maximum product energy ((BH)max) which is 16% higher than that of melt-spun ribbons. We also studied the temperature dependence of the coercivity in a temperature range of 300-500 K, and proposed that the coercivity of melt-spun (Nd0.8Ce0.2)2.4Fe12Co?B ribbons with ferromagnetic GB phase at room temperature was from the combination of strong domain-wall pinning and nucleation. The same mechanism works in the annealed ribbons.

| S-EPMC5615716 | biostudies-literature

[Si(O2 C6 F4 )2 ]14 : Self-Assembly of a Giant Perfluorinated Macrocyclic Host by Low-Barrier Si-O Bond Metathesis.

Project description:The dynamic covalent self-assembly of 14 units of bis(perfluorocatecholato)silane leads to [Si(O2 C6 F4 )2 ]14 -the first giant perfluorinated macrocycle. The oligomerization process is monitored spectroscopically, and the macrocycle analyzed by single-crystal X-ray diffraction. The molecule forms a rigid cavity that can host two o-closo-dodecacarboranes. Computations rationalize the consistent and reproducible formation of the 14mer and disclose a non-catalyzed Si-O/ Si-O σ-bond metathesis with an exceptionally low energetic barrier. For the first time, the most prevalent linker in our geosphere-SiO4 -is disposed to construct a shape-defined crystalline macromolecule.

| S-EPMC7756369 | biostudies-literature