Search results for "Magnetization"
showing 10 items of 550 documents
A [Cr2Ni] coordination polymer: slow relaxation of magnetization in quasi-one-dimensional ferromagnetic chains
2018
The reaction of [Cr3IIIO(OAc)6(H2O)3]NO3·AcOH with 2-hydroxynaphthaldehyde, 2-amino-isobutyric acid and NiCl2·6H2O in MeOH, under basic and solvothermal conditions, led to the formation of the quasi-1D coordination polymer {[CrIII2NiII(L)4(MeOH)2]}n (where L = the dianion of the Schiff base between 2-hydroxynaphthaldehyde and 2-amino-isobutyric acid), which behaves as a ferromagnetic chain, displaying slow relaxation of magnetization.
Ferromagnetic and paramagnetic magnetization of implanted GaN:Ho,Tb,Sm,Tm films
2015
The SQUID magnetic measurements were performed on the GaN films prepared by metal-organic vapour phase epitaxy and implanted by Tb3+, Tm3+, Sm3+, and Ho3+ ions. The sapphire substrate was checked by the electron paramagnetic resonance method which showed a content of Cr3+ and Fe3+ impurities. The samples 5 × 5 mm2 were positioned in the classical straws and within an estimated accuracy of 10−6 emu, no ferromagnetic moment was detected in the temperature region of 2–300 K. The paramagnetic magnetization was studied for parallel and perpendicular orientation. In the case of GaN:Tb sample, at T = 2 K, a pronounced anisotropy with the easy axis perpendicular to the film was observed which can b…
Ferromagnetic exchange interaction in a new Ir(iv)-Cu(ii) chain based on the hexachloroiridate(iv) anion.
2019
The iridium(IV) complex (NBu4)2[IrCl6] (1) has been synthetised, characterised and used as a precursor to prepare the new chloro-bridged heterobimetallic IrIV–CuII chain of formula {IrCl5(μ-Cl)Cu(viim)4}n (2) [viim = 1-vinylimidazole]. The crystal structure and magnetic properties of 1 and 2 have been investigated. Both compounds crystallise in the monoclinic system with space group C2/c. Each IrIV ion in both 1 and 2 is six-coordinate and bonded to six chloride ions in a regular octahedral geometry. In compound 2, the CuII ion exhibits an axially elongated octahedron with four N atoms, from four monodentate viim ligands, that form the equatorial plane, and two chloride ions that occupy the…
Magnetic resonance study of bulk and thin film EuTiO3
2017
Magnetic resonance spectra of EuTiO3 in both bulk and thin film form were taken at temperatures from 3-350 K and microwave frequencies from 9.2-9.8 and 34 GHz. In the paramagnetic phase, magnetic resonance spectra are determined by magnetic dipole and exchange interactions between Eu2+ spins. In the film, a large contribution arises from the demagnetization field. From detailed analysis of the linewidth and its temperature dependence, the parameters of spin-spin interactions were determined: the exchange frequency is 15-15.5 GHz and the estimated critical exponent of the spin correlation length is ~ 0.5. In the bulk samples, the spectra exhibited a distinct minimum in the linewidth at the N…
Charge and spin photocurrents in the Rashba model
2017
In metallic noncentrosymmetric crystals and at surfaces the response of spin currents and charge currents to applied electric fields contains contributions that are second order in the electric field, which are forbidden by symmetry in centrosymmetric systems. Thereby, photocurrents and spin photocurrents can be generated in inversion asymmetric metals by the application of femtosecond laser pulses. We study the laser-induced charge current in the ferromagnetic Rashba model with in-plane magnetization and find that this \textit{magnetic photogalvanic effect} can be tuned to be comparable in size to the laser-induced photocurrents measured experimentally in magnetic bilayer systems such as C…
Relaxation of remnant magnetisation in YBa2Cu3O7−δ films
2007
Abstract The relaxation of the remnant magnetisation in optimally doped disk-shaped YBa2Cu3O7−δ films with the initially applied magnetic field H oriented along the c axis was measured using dc SQUID magnetometry. The temperature (T) dependence of the experimentally observed normalised magnetisation relaxation rate S exhibits three distinct regions. At high T, S(T) increases with increasing T, which can be explained in terms of plastic vortex creep. The well known plateau in the S(T) variation at intermediate T appears to be caused by collective (elastic) creep in a dynamically ordered vortex system. At low T, where S increases again with increasing T, the magnetisation relaxation is not in…
Electrical and Magnetic Properties of Graphene Films with Ni Nanoparticles
2015
Electrical properties and magnetic properties of graphene oxide and reduced graphene oxide films with addition of Ni nanoparticles were investigated. It is found that reduction of GO by Hydrazine hydrate (HH) and subsequent mixing with Ni NPs yields a higher current (10(-5)A) compared to the samples where GO is first mixed with Ni NPs and further reduced (10(-6)A). At the same time, GO sample prepared by addition of Ni NPs to GO with subsequent reduction by HH presents the largest hysteresis with Mr as high as 11.8emu/g. Moreover, mixing of Ni NPs with HH before addition to GO or addition of Ni NPs to already reduced GO yields smaller values of the magnetization. Thus, the optimal procedure…
Slow Magnetization Relaxation in a 1-D Double-Chain Coordination Polymer Composed of {Dy<sup>III</sup> <sub>4</sub>} Repeatin…
2013
The "unsuccessful" synthesis of the non-commercially available 'Dy(O2CPh)3' precursor from the stoichiomet- ric reaction of Dy(NO3)3·5H2O with 3 equivalents of NaO2CPh in MeCN/H2O has led instead to the "successful" isolation and structural characterization of the 1-D coordination polymer (Dy4(O2CPh)12(H2O)8)n·2n(PhCO2H)·n(MeCN) (1·2n(PhCO2H)·n(MeCN)) in excellent yields (~90%). The one-dimensional double-chain structure of 1 was resulted from the linkage of two parallel chains by syn,anti-� 1 :� 1 :μ PhCO2 - groups. The lattice structure of 1 is further extended to a 2-D network through hydrogen bonding and - stacking interactions. The observation of out-of-phase (� �� M) ac susceptibility…
Photo-switching in a hybrid material made of magnetic layered double hydroxides intercalated with azobenzene molecules.
2014
Financial support from the EU (Projects HINTS FP7-263104-2 and SpinMol Advanced Grant ERC-2009-AdG-20090325), the Spanish Ministerio de Economia y Competitividad (Projects with FEDER cofinancing MAT 2009-14528-C02-01, MAT2011-22785, MAT2012-38567-C02-01, CTQ-2011-26507, Consolider-Ingenio in Molecular Nanoscience CSD2007-00010, Consolider-Ingenio 2010-Multicat CSD2009-00050, and Severo Ochoa Program SEV-2012-0267), Generalitat Valenciana (PROMETEO and ISIC-Nano programs), and VLC/Campus Microcluster "Functional Nanomaterials and Nanodevices" is gratefully acknowledged. C. M. G. thanks the Spanish MINECO for a Ramon y Cajal Fellowship (RYC-2012-10894). We also acknowledge P. Atienzar and J. …
The surface chemistry of iron oxide nanocrystals: surface reduction of γ-Fe2O3 to Fe3O4 by redox-active catechol surface ligands
2018
The effect of surface functionalization on the structural and magnetic properties of catechol-functionalized iron oxide magnetic (γ-Fe2O3) nanocrystals was investigated. γ-Fe2O3 nanocrystals (NCs) were synthesized from iron acetyl acetonate in phenyl ether with 1,2-tetradecanediol, oleic acid, and oleylamine. X-ray powder diffraction in combination with Mossbauer spectroscopy revealed the presence of γ-Fe2O3 (maghemite) particles only. Replacement of oleic acid (OA) with catechol-type 3,4-dihydroxyhydrocinnamic acid (DHCA) or polydentate polydopamine acrylate (PDAm) surface ligands leads to a pronounced change of the magnetic behavior of the γ-Fe2O3 nanocrystals and separated them into two …