Search results for "Ferromagnetic"
showing 10 items of 81 documents
Synthesis, characterization and magnetism of monodispersed water soluble palladium nanoparticles
2008
Water soluble, monodispersed Pd nanoparticles with a narrow particle size distribution have been successfully synthesized by controlled reduction of [PdCl4]2−. The resulting aqueous colloids are stable over extended periods of time and can be prepared at high nanoparticle loading (20 g/L of Pd) with no agglomeration. The size of the nanoparticles can be reduced from the nanometer (ca. 3.5 nm) to the sub-nanometer size range (ca. 0.9 nm). Detailed magnetic characterization indicated that the larger, 3.5 nm nanoparticles show ferromagnetic properties at room temperature, while the sub-nanometric ones lose this magnetic behavior.
Strain-controlled domain wall injection into nanowires for sensor applications
2021
We investigate experimentally the effects of externally applied strain on the injection of 180$^\circ$ domain walls (DW) from a nucleation pad into magnetic nanowires, as typically used for DW-based sensors. In our study the strain, generated by substrate bending, induces in the material a uniaxial anisotropy due to magnetoelastic coupling. To compare the strain effects, $Co_{40}Fe_{40}B_{20}$, $Ni$ and $Ni_{82}Fe_{18}$ samples with in-plane magnetization and different magnetoelastic coupling are deposited. In these samples, we measure the magnetic field required for the injection of a DW, by imaging differential contrast in a magneto-optical Kerr microscope. We find that strain increases t…
A novel two-dimensional honeycomb-like bimetallic iron(iii)–nickel(ii) cyanide-bridged magnetic material [Ni(cyclam)]3[Fe(CN)6]2·nH2O (cyclam = 1,4,8…
1999
The 2D honeycomb-like layered iron(iii)–nickel(ii) cyanidebridged complex [Ni(cyclam)]3[Fe(CN)6]2·nH2O exhibits ferromagnetic intralayer and antiferromagnetic interlayer interactions; above 3 K the magnetic properties are typical of a metamagnet with Hc = 5000 G, whereas below 3 K a canted structure is formed, leading to a long range ferromagnetic ordering. Lloret Pastor, Francisco, Francisco.Lloret@uv.es
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…
Seed layer technique for high quality epitaxial manganite films
2016
We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening tempera…
Characterization of microscopic ferromagnetic defects in thin films using magnetic microscope based on Nitrogen-Vacancy centres
2020
In this work we present results acquired by applying magnetic field imaging technique based on Nitrogen-Vacancy centres in diamond crystal for characterization of magnetic thin films defects. We used the constructed wide-field magnetic microscope for measurements of two kinds of magnetic defects in thin films. One family of defects under study was a result of non-optimal thin film growth conditions. The magnetic field maps of several regions of the thin films created under very similar conditions to previously published research revealed microscopic impurity islands of ferromagnetic defects, that potentially could disturb the magnetic properties of the surface. The second part of the measur…
Enhancement of spin Hall conductivity in W-Ta alloy
2020
Generating pure spin currents via the spin Hall effect in heavy metals has been an active topic of research in the last decade. In order to reduce the energy required to efficiently switch neighbouring ferromagnetic layers for applications, one should not only increase the charge- to-spin conversion efficiency but also decrease the longitudinal resistivity of the heavy metal. In this work, we investigate the spin Hall conductivity in W_{1-x}Ta_{x} / CoFeB / MgO (x = 0 - 0.2) using spin torque ferromagnetic resonance measurements. Alloying W with Ta leads to a factor of two change in both the damping-like effective spin Hall angle (from - 0.15 to - 0.3) and longitudinal resistivity (60 - 120…
Gold Nanowired: A Linear (Au25)n Polymer from Au25 Molecular Clusters
2014
Au25(SR)18 has provided fundamental insights into the properties of clusters protected by monolayers of thiolated ligands (SR). Because of its ultrasmall core, 1 nm, Au25(SR)18 displays molecular behavior. We prepared a Au25 cluster capped by n-butanethiolates (SBu), obtained its structure by single-crystal X-ray crystallography, and studied its properties both experimentally and theoretically. Whereas in solution Au25(SBu)18(0) is a paramagnetic molecule, in the crystal it becomes a linear polymer of Au25 clusters connected via single Au-Au bonds and stabilized by proper orientation of clusters and interdigitation of ligands. At low temperature, [Au25(SBu)18(0)]n has a nonmagnetic ground s…
Mössbauer and magnetic studies of mixed-valence linear chain compounds: Na3Fe2S4 and Na3Fe2Se4
1986
Mossbauer and magnetic data establish the two compounds Na3Fe2X4(X=S, Se) as mixed-valence linear chain compounds with rapid valence fluctuation. The compounds exhibit 1-dimensional antiferromagnetic coupling within the chains, and below a critical temperature a 3-dimensional ferrimagnetic ordering between the chains.
Element-Specific Magnetic and Electronic Properties of Epitaxial Heusler Films
2015
X-ray magnetic circular dichroism (XMCD) provides an experimental access to element-specific electronic properties of thin epitaxial films of Heusler alloys. The combination of bulk-sensitive transmission and surface-sensitive electron yield methods reveals quantitative information on bulk and interface properties. Extreme cases of magnetically dead and life layers at interfaces illustrate the high potential of XMCD. The dependence of XMCD on disorder, structure and composition is discussed as well as dynamic properties investigated by a combination of ferromagnetic resonance and XMCD. Examples are shown where spectroscopic information provided by XMCD is exploited to discuss subtle changes…