Magnetoelectric Multiferroicity and Magnetic Anisotropy in Guanidinium Copper(II) Formate Crystal

Hybrid metal-organic compounds as relatively new and prosperous magnetoelectric multiferroics provide opportunities to improve the polarization, magnetization and magneto-electric coupling at the same time, which usually have some limitations in the common type-I and type-II multiferroics. In this work we investigate the crystal of guanidinium copper (II) formate [C(NH2)3]Cu(HCOO)3 and give novel insights concerning the structure, magnetic, electric and magneto-electric behaviour of this interesting material. Detailed analysis of crystal structure at 100 K is given. Magnetization points to the copper (II) formate spin-chain phase that becomes ordered below 4.6 K into the canted antiferromagnetic (AFM) state, as a result of super-exchange interaction over different formate bridges. The performed ab-initio colinear density functional theory (DFT) calculations confirm the AFM-like ground state as a first approximation and explain the coupling of spin-chains into the AFM ordered lattice. In versatile measurements of magnetization of a crystal, including transverse component besides the longitudinal one, very large anisotropy is found that might originate from canting of the coordination octahedra around copper (II) in cooperation with the canted AFM order. With cooling down in zero fields the generation of spontaneous polarization is observed step-wise below 270 K and 210 K and the effect of magnetic field on its value is observed also in the paramagnetic phase. Measured polarization is somewhat smaller than the DFT value in the c-direction, possibly due to twin domains present in the crystal. The considerable magneto-electric coupling below the magnetic transition temperature is measured with different orientations of the crystal in magnetic field, giving altogether the new light onto the magneto-electric effect in this material.

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Ferrimagnetic Half-Metallicity of the New Quaternary Heusler Alloy CoCrScIn: FP-LAPW Method

SPIN ◽

10.1142/s201032472150017x ◽

2021 ◽

Vol 11 (02) ◽

pp. 2150017

Author(s):

Halima Hamada ◽

Keltouma Boudia ◽

Friha Khelfaoui ◽

Kadda Amara ◽

Toufik Nouri ◽

...

Keyword(s):

Magnetic Moment ◽

Density Functional ◽

Structural Parameters ◽

Magnetic Transition ◽

Plane Waves ◽

Full Potential ◽

Half Metallicity ◽

Metallic Behavior ◽

Magnetic Transition Temperature ◽

Half Metallic

The structural, electronic, elastic and magnetic properties of CoCrScIn were investigated using first principle calculations with applying the full-potential linearized augmented plane waves (FP-LAPW) method, based totally on the density functional theory (DFT). After evaluating the results, the calculated structural parameters reveal that CoCrScIn compound is stable in its ferrimagnetic configuration of the type-III structure. The mechanical properties show its brittle and stiffer behavior. The formation energy value showed that CoCrScIn can be experimentally synthesized. Additionally, the obtained band structures and density of states (DOS) reflect the half-metallic behavior of CoCrScIn, with an indirect bandgap of 0.43[Formula: see text]eV. The total magnetic moment of 3[Formula: see text][Formula: see text] and half-metallic ferrimagnetic state are maintained in the range 5.73–6,79 Å. The magnetic moment especially issues from the Cr-[Formula: see text] and Co-[Formula: see text] spin-polarizations. Furthermore, the calculations of Curie temperature reveal that CoCrScIn has high magnetic transition temperature of 836.7[Formula: see text]K.

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MAGNETIC PROPERTIES AND MAGNETOCALORIC EFFECT OF HYDROGEN TREATED Gd-BASED BULK METALLIC GLASS

International Journal of Modern Physics B ◽

10.1142/s0217979212500415 ◽

2012 ◽

Vol 26 (05) ◽

pp. 1250041

Author(s):

Q. ZHENG ◽

H. FU ◽

M. X. WANG

Keyword(s):

Magnetic Field ◽

Metallic Glass ◽

Interatomic Distance ◽

Magnetic Transition ◽

Amorphous Structure ◽

Magnetic Entropy ◽

Magnetic Transition Temperature ◽

Entropy Changes ◽

The Magnetic Field ◽

Absorption Of Hydrogen

The metallic glass Gd 52.5 Co 18.5 Al 28 Zr 1 preserves the amorphous structure after hydrogenation at 473 K for 48 h. The absorption of hydrogen leads to the reduction of the magnetic transition temperature due to the expansion of the interatomic distance. The magnetic anisotropy is introduced and the coercivity and remanence are 352 Oe and 12.5 emu/g at 1.8 K, respectively. The maxima of magnetic entropy changes are 11.3 and 7.5 J/kg K with the magnetic field changes of 0 to 70 kOe and 0 to 50 kOe, respectively. The decline of the magnetic entropy changes can be attributed to the disappearance of the collinear ferromagnetic characteristics and the difficulty of saturation for the magnetization after hydrogenation.

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Direct imaging of magnetic field-driven transitions of skyrmion cluster states in FeGe nanodisks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1600197113 ◽

2016 ◽

Vol 113 (18) ◽

pp. 4918-4923 ◽

Cited By ~ 72

Author(s):

Xuebing Zhao ◽

Chiming Jin ◽

Chao Wang ◽

Haifeng Du ◽

Jiadong Zang ◽

...

Keyword(s):

Magnetic Field ◽

Elevated Temperatures ◽

Magnetic Transition ◽

Magnetic Nanostructures ◽

Cluster States ◽

Magnetic Transition Temperature ◽

Transmission Electron ◽

Lorentz Transmission Electron Microscopy ◽

The Magnetic Field ◽

Nontrivial Topology

Magnetic skyrmion is a nanosized magnetic whirl with nontrivial topology, which is highly relevant for applications on future memory devices. To enable the applications, theoretical efforts have been made to understand the dynamics of individual skyrmions in magnetic nanostructures. However, directly imaging the evolution of highly geometrically confined individual skyrmions is challenging. Here, we report the magnetic field-driven dynamics of individual skyrmions in FeGe nanodisks with diameters on the order of several skyrmion sizes by using Lorentz transmission electron microscopy. In contrast to the conventional skyrmion lattice in bulk, a series of skyrmion cluster states with different geometrical configurations and the field-driven cascading phase transitions are identified at temperatures far below the magnetic transition temperature. Furthermore, a dynamics, namely the intermittent jumps between the neighboring skyrmion cluster states, is found at elevated temperatures, at which the thermal energy competes with the energy barrier between the skyrmion cluster states.

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Structure in the radiation of the galactic disk

Symposium - International Astronomical Union ◽

10.1017/s0074180900101184 ◽

1967 ◽

Vol 31 ◽

pp. 355-356

Author(s):

R. D. Davies

Keyword(s):

Magnetic Field ◽

Galactic Disk ◽

Galactic Magnetic Field ◽

Measured Polarization

Observations at various frequencies between 136 and 1400 MHz indicate a considerable amount of structure in the galactic disk. This result appears consistent both with measured polarization percentages and with considerations of the strength of the galactic magnetic field.

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Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding

10.26434/chemrxiv.10316681.v1 ◽

2019 ◽

Author(s):

Andrew Rosen ◽

M. Rasel Mian ◽

Timur Islamoglu ◽

Haoyuan Chen ◽

Omar Farha ◽

...

Keyword(s):

Density Functional ◽

Metal Organic Frameworks ◽

Redox Activity ◽

Screening Methods ◽

Bridging Ligands ◽

Metal Centers ◽

Computational Screening ◽

Open Metal Sites ◽

Metal Organic ◽

Unsaturated Metal Sites

Metal−organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O2 and N2 adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering μ-Br-, μ-Cl-, μ-F-, μ-SH-, or μ-OH- groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O2 affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O2. In contrast with O2 adsorption, N2 adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V2+ open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl- ligands of M2Cl2(BBTA) (H2BBTA = 1H,5H-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH- groups would significantly enhance the strength of O2 adsorption at the open metal sites without a corresponding increase in the N2 affinity. Experimental investigation of Co2Cl2(BBTA) and Co2(OH)2(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O2 at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH- ligands and the presence of H-bonding interactions between the μ-OH- bridging ligands and the O2 adsorbate.

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A Solvent Free Synthetic Route for Cerium(IV) Metal-Organic Frame-works with UiO-66 Architecture and Their Photocatalytic Application

10.26434/chemrxiv.9199634.v1 ◽

2019 ◽

Author(s):

Matteo Campanelli ◽

Tiziana Del Giacco ◽

Filippo De Angelis ◽

Edoardo Mosconi ◽

Marco Taddei ◽

...

Keyword(s):

Density Functional ◽

Chemical Oxidation ◽

Solvent Free ◽

Cerium Ammonium Nitrate ◽

Benzylic Alcohols ◽

Near Ultraviolet ◽

Photocatalytic Application ◽

Activity Density ◽

Ultraviolet Light Irradiation ◽

Metal Organic

<div> A novel solvent-free synthesis for Ce-UiO-66 metal-organic frameworks (MOFs) is presented. The MOFs are obtained by simply grinding the reagents, cerium ammonium nitrate (CAN) and the carboxylic linkers, in a mortar for few minutes with the addition of a small amount of acetic acid (AcOH) as modulator (1.75 eq, o.1 ml). The slurry is then transferred into a 1 ml vial and heated at 120°C for 1 day. The MOFs have been characterized for their composition, crystallinity and porosity and employed as heterogenous catalysts for the photo-oxidation reaction of substituted benzylic alcohols to benzaldaldehydes under near ultraviolet light irradiation. The catalytic performances, such as yield, conversion and kinetics, exceed those of similar systems studied by chemical oxidation and using Ce-MOF as catalyst. Moreover, the MOFs were found to be reusable up to three cycles without loss of activity. Density functional theory (DFT) calculations gave an estimation of the band-gap shift due to the different nature of the linkers used and provide useful information on the catalytic activity experimentally observed. </div>

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Density Functional Investigation of the Conversion of Furfural to Furfuryl Alcohol by Reaction with i-Propanol over UiO-66 Metal–Organic Framework

Inorganic Chemistry ◽

10.1021/acs.inorgchem.0c03764 ◽

2021 ◽

Author(s):

Jarinya Sittiwong ◽

Sininat Boonmark ◽

Watinee Nunthakitgoson ◽

Thana Maihom ◽

Chularat Wattanakit ◽

...

Keyword(s):

Furfuryl Alcohol ◽

Density Functional ◽

Metal Organic Framework ◽

Metal Organic ◽

Functional Investigation ◽

Organic Framework

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Selective capture of carbon dioxide from hydrocarbons using a metal-organic framework

Nature Communications ◽

10.1038/s41467-020-20489-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Omid T. Qazvini ◽

Ravichandar Babarao ◽

Shane G. Telfer

Keyword(s):

Carbon Dioxide ◽

Density Functional ◽

Metal Organic Framework ◽

Density Functional Theory Calculations ◽

Time Lags ◽

X Ray Crystallography ◽

Metal Organic ◽

Adsorption Of Co ◽

Short Time ◽

Organic Framework

AbstractEfficient and sustainable methods for carbon dioxide capture are highly sought after. Mature technologies involve chemical reactions that absorb CO2, but they have many drawbacks. Energy-efficient alternatives may be realised by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO2. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16. This metal-organic framework captures CO2 with a high affinity in its one-dimensional channels, as determined by adsorption isotherms, X-ray crystallography and density-functional theory calculations. Its low affinity for other competing gases delivers high selectivity for the adsorption of CO2 over methane, acetylene, ethylene, ethane, propylene and propane. For equimolar mixtures of CO2/CH4 and CO2/C2H2, the selectivity is 6690 and 510, respectively. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products, including pure methane and acetylene.

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