Search results for "Magnetization"
showing 10 items of 550 documents
Spin-orbit torques and tunable Dzyaloshinskii-Moriya interaction in Co/Cu/Co trilayers
2017
We study the spin-orbit torques (SOTs) in Co/Cu/Co magnetic trilayers based on first-principles density-functional theory calculations in the case where the applied electric field lies in-plane, i.e., parallel to the interfaces. We assume that the bottom Co layer has a fixed in-plane magnetization, while the top Co layer can be switched. We find that the SOT on the top ferromagnet can be controlled by the bottom ferromagnet because of the nonlocal character of the SOT in this system. As a consequence the SOT is anisotropic, i.e., its magnitude varies with the direction of the applied electric field. We show that the Dzyaloshinskii-Moriya interaction (DMI) in the top layer is anisotropic as …
Magnetic properties of the TbMn2 single crystals
1999
Abstract Single crystals of TbMn 2 were grown by the Czochralski method from a levitated melt. Results of electrical resistivity, magnetization in strong magnetic fields along the principal crystallographic directions, AC and DC magnetic susceptibility and the temperature dependence of the lattice parameter are presented.
Local structure and magnetization of ferromagnetic Cu-doped ZnO films: No magnetism at the dopant?
2016
Abstract Relationship between magnetism and structure of Cu-doped ZnO was investigated at macroscopic and microscopic levels. Thin Zn1−xCuxO films (x = 0.02, 0.04, 0.07 and 0.10) were prepared by a pulsed laser deposition and characterized via superconducting quantum interference device (SQUID) magnetometry, high-resolution x-ray diffraction, and Cu K-edge and Zn K-edge x-ray absorption, x-ray linear dichroism and x-ray circular magnetic dichroism spectroscopy. Even though the samples exhibit room-temperature ferromagnetism with magnetization that increases with Cu concentration, we did not detect signatures of local magnetic moments associated with Cu atoms, as evidenced by the lack of any…
Magnetization relaxation in the flux-creep annealing regime across the second magnetization peak of disordered YBa2Cu3O7− crystals
2001
Abstract The relaxation of the irreversible magnetization of disordered YBa 2 Cu 3 O 7− x crystals measured in the “flux-creep annealing” regime reveals that across the second magnetization peak (SMP) the barriers against flux motion remain finite at low current densities, which supports the existence of a crossover to a dissipation process involving the plastic deformation of the vortex system. In our experiments, the vortex creep process appears to be exclusively controlled by collective pinning barriers (diverging at low current densities) only below the onset of the SMP, where the vortex system is stable against dislocation formation. The (elastic) collective pinning barriers observed f…
Field-induced slow relaxation of magnetisation in an anionic heterotetranuclear [ZnIIReIV3] system
2019
The compound (NBu4)4[ZnII{ReIVCl4(μ-ox)}3] (1) [NBu4+ = tetra-n-butylammonium cation and ox2− = oxalate dianion] is the first example of an oxalato-bridged ZnII system coordinated to a 5d metal ion that exhibits slow relaxation of magnetisation.
Spontaneous Magnetization in Heterometallic NiFe-MOF-74 Microporous Magnets by Controlled Iron Doping
2017
We report the direct synthesis of mixed-metal NiFe-MOF-74 solids that display combination of porosity with ferrimagnetic ordering. Compared to the undoped Ni phase, controlled doping with Fe enables to modify intra and interchain magnetic interactions for the onset of spontaneous magnetization at temperatures fixed by the doping level. Synthesis of porous magnets remains somewhat elusive due to the difficulties in isolating foreseeable metal-organic architectures that combine small bridging linkers, for strong magnetic coupling, with polyaromatic connectors responsible for porosity. In turn, we demonstrate that metal doping is better fitted to modify the magnetism of Metal-Organic Framework…
An Ising ferromagnet with an antiferromagnetic surface layer: A simple model for magnetic surface reconstruction
1985
Simple cubic Ising lattices are studied by Monte Carlo simulation, using a thin film geometry (usually 40 atomic layers thick), with nearest neighbour ferromagnetic exchange J in the bulk and nearest neighbour antiferromagnetic interaction Js between surface spins. Applying a technique of preferential sampling in the surface layers, we investigate the ordering for a variety of values of JsJ and for various temperatures. For JsAF < Js < − 0.25J (where JsAF ≈ − 2.01J) ferromagnetic ordering occurs at a higher temperature than the antiferromagnetic surface ordering, while for − 0.25J < Js no antiferromagnetic long range order is possible. For Js < JsAF the surface transition occurs at a higher…
Electronic, structural, and magnetic properties of the half-metallic ferromagnetic quaternary Heusler compounds CoFeMnZ(Z=Al, Ga, Si, Ge)
2011
The quaternary intermetallic Heusler compounds CoFeMn$Z$ ($Z=\text{Al}$, Ga, Si, or Ge) with $1:1:1:1$ stoichiometry were predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations. The compounds were synthesized using an arc-melting technique and the crystal structures were analyzed using x-ray powder diffraction. The electronic properties were investigated using hard x-ray photoelectron spectroscopy. The low-temperature magnetic moments, as determined from magnetization measurements, follow the Slater-Pauling rule, confirming the proposed high spin polarizations. All compounds have high Curie temperatures, allowing for applications at room temperature…
Torsion oscillation magnetometry (TOM) of Fe films on Ni(111)/W(110) substrates
1999
Abstract Fe films 2–20 atomic monolayers (ML) thick have been deposited on Ni(1 1 1) films (4–60 ML) prepared on W(1 1 0) under UHV conditions. The Ni(1 1 1) films grow in a Nishijama–Wassermann orientation with a 3.6% lattice expansion along Ni[2 1 1] (‖ W[1 1 0]). On top of these slightly distorted Ni films iron is observed to grow preferentially in two mirror orientations. The saturation magnetization of these Fe films and the anisotropies of Fe/Ni bilayers have been studied using torsion oscillation magnetometry. The magnetization of the Fe films of 2.13 μB per atom is close to the bulk value of Fe. The out-of-plane surface (interface) anisotropy constant KFeNis=(−0.65±0.15) mJ/m2 of th…
Analysis of magnetization relaxation in MgB2 bulk samples obtained by electric-field assisted sintering
2008
Abstract The relaxation of the irreversible magnetization of MgB2 bulk samples obtained by electric-field assisted sintering was investigated using the SQUID magnetometry for a magnetic field H up to 50 kOe applied in zero-field-cooling conditions. We observed a crossover plastic creep at high temperatures T-elastic creep at low T, described by H ∝ T−2 in the low T range, which appears to be caused by the macroscopic currents induced in the sample during magnetization measurements. By decreasing T below this line the determined creep exponent rapidly overcomes the widely accepted theoretical values for elastic (collective) pinning. This behaviour can easily be explained through the occurren…