Search results for "Coercivity"
showing 10 items of 74 documents
STRUCTURE AND MAGNETIC PROPERTIES OF COBALT FERRITE PARTICLES PRODUCED BY METHOD OF PYROLYTIC SYNTHESIS
2008
ABSTRACT Magnetic fine particles of cobalt ferrite have been prepared by method of pyrolytic synthesis. X-ray diffraction confirmed the formation of single-phase cobalt ferrite nanoparticles in the range 6–50 nm. The size of the particles varies depending on matrix dispersity and mass content in the organic precursors. A large coercivity observed to be small for smaller single-domain particles due to superparamagnetic behavior.
Metal-organic magnets with large coercivity and ordering temperatures up to 242°C.
2020
International audience; Magnets derived from inorganic materials (e.g., oxides, rare-earth–based, and intermetallic compounds) are key components of modern technological applications. Despite considerable success in a broad range of applications, these inorganic magnets suffer several drawbacks, including energetically expensive fabrication, limited availability of certain constituent elements, high density, and poor scope for chemical tunability. A promising design strategy for next-generation magnets relies on the versatile coordination chemistry of abundant metal ions and inexpensive organic ligands. Following this approach, we report the general, simple, and efficient synthesis of light…
Polarization of SrBi 2 Ta 2 O 9 ceramics at infra‐low frequencies
2009
Dielectric response in the SrBi2Ta2O9 ceramics is studied over a wide range of temperatures at fields up to Emax ≈ 18 kV/cm. Dependence of dielectric permittivity on field intensity is analyzed at different temperatures. A series of polarization loops are obtained at frequencies 0.1 Hz, 1 Hz, and 10 Hz. The hysteresis at switching polarization is displayed by the shape of polarization loops changing with the field amplitude from bi-angles to quasi-saturated loop patterns of a high degree of rectangularity. The ratio of remnant polarization to maximum polarization as function of field amplitude is presented. Thermal behaviour of the coercive field and the half-width of polarization loops is …
Impact of gadolinium on the structure and magnetic properties of nanocrystalline powders of iron oxides produced by the extraction-pyrolytic method
2020
The work has been done in frame of the TransFerr project. It has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 778070. This research was also supported by Latvian Research Council project lzp-2018/1-0214. A.I.P. appreciates support from the Estonian Research Council grant (PUT PRG619).
An unusual magnetic response in a π-stacked 66-dia net structure of [4 + 2] copper(II) cubane
2015
A phenoxo bridged antiferromagnetic copper(II) cubane features a π-stacked 66-dia net framework and creates long range ferromagnetic ordering, as evidenced from a coercivity maximum (∼2000 Oe) at 20 K with very unusual saturation magnetization.
Long‐Range Order in Layered Perovskite Salts – Structure and Magnetic Properties of [(CH 3 ) 2 CHCH 2 NH 3 ] 2 CuX 4 (X = Cl, Br)
2012
The synthesis, structure, and magnetic properties of two new layered perovskite-type copper halide salts are reported. Dominant ferromagnetic coupling is observed with J/k = 14.58(1) and 21.5(4) K for the Cl and Br salts, respectively. For [(iBA)2CuCl4] (1); (iBA = isobutylammonium): P21/c with a = 13.9481(8) A, b = 7.5061(4) A, c = 7.5133(4) A and β = 102.520(1)° with Z = 4. In this structure, planar CuCl42– ions are linked together into layers of corner-sharing distorted octahedra. Ferromagnetic ordering occurs at Tc = 6.5 K for 1 with spin canting. Hysteresis loops show a coercive field of 2 mT with rapid saturation at 2 K that persists up to T = 9 K. The bromide salt is not isomorphous …
Unusual Magnetic Behavior in the Layered Ferromagnet [Ni(C6H14N2)2]3[Fe(CN)6]2·2H2O
2002
The cyano-bridged molecular complex [Ni(C6H14N2)2]3[Fe(CN)6]2·2H2O, with a rectangular 2D structure, displays long-range ferromagnetic ordering at 14 K, and exhibits unusual magnetic properties for this type of material, as confirmed by the appearance of two different peaks in the AC magnetic susceptibility plot, and a high coercive field (2.3 kOe) and remnant magnetization (6.8 μB). (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
A Dysprosium Metallocene Single-Molecule Magnet Functioning at the Axial Limit
2017
Abstraction of a chloride ligand from the dysprosium metallocene [(Cpttt)2DyCl] (1Dy Cpttt=1,2,4‐tri(tert‐butyl)cyclopentadienide) by the triethylsilylium cation produces the first base‐free rare‐earth metallocenium cation [(Cpttt)2Dy]+ (2Dy) as a salt of the non‐coordinating [B(C6F5)4]− anion. Magnetic measurements reveal that [2Dy][B(C6F5)4] is an SMM with a record anisotropy barrier up to 1277 cm−1 (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low‐lying Kramers doub…
Spectroscopic Signature of the Superparamagnetic Transition and Surface Spin Disorder in CoFe2O4 Nanoparticles
2012
Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of CoFe(2)O(4) nanoparticles and compared our results to trends in the coercivity over the same size range and to the response of the bulk material. Remarkably, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm. A spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the magnetically disordered shell thickness, which increases from 0.4 nm i…
Giant magnetic anisotropy energy and coercivity in Fe island and atomic wire on W(110)
2012
We have directly investigated the giant magnetic anisotropy energy and coercivity of monolayer (ML) Fe islands and stripes on flat and stepped W(110) surfaces using x-ray magnetic circular dichroism. Both for islands and stripes, the magnetic anisotropy energy is $\ensuremath{\sim}$1.0 meV/atom, independent of the coverage below 0.5 ML. On the contrary, the coercive field of the islands rapidly drops from 4.3 T at 0.25 ML to 1.9 T at 0.50 ML, while that of the stripes moderately degrades from 3.5 T at 0.15 ML ($\ensuremath{\sim}$3 atom rows) to 3.0 T at 0.50 ML. We explain the contrastive behavior for the islands and stripes by different nucleation and remagnetization processes. Considering…