Search results for "Magnetization"
showing 10 items of 550 documents
Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field
2015
AbstractThe reversal of the magnetization under the influence of a field pulse has been previously predicted to be an incoherent process with several competing phenomena such as domain wall relaxation, spin wave-mediated instability regions and vortex-core mediated reversal dynamics. However, there has been no study on the direct observation of the switching process with the aid of a microwave signal input. We report a time-resolved imaging study of magnetization reversal in patterned magnetic structures under the influence of a field pulse with microwave assistance. The microwave frequency is varied to demonstrate the effect of resonant microwave-assisted switching. We observe that the swi…
Surface hysteresis curves of Fe(110) and Fe(100) crystals in ultrahigh vacuum — evidence of adsorbate influences
1992
Abstract We have investigated hysteresis curves of silicon-stabilized Fe(100) and Fe(110) crystals using Polarized Secondary Electron Emission (PSEE) for surface magnetization processes and Magneto-Optical Kerr Effect (MOKE) for bulk hysteresis curves. In particular, the influence of adsorbates (oxygen and sulphur) and surface roughness on the magnetization reversal has been studied. For surface hysteresis curves we found adsorbate-induced reductions of coercive force of up to 50%; the bulk hysteresis curves showed significantly smaller deviations. Similar changes were caused by surface disorder on an atomic scale induced by ion bombardment. The results agree qualitatively with a previous e…
Microscopic origin of magnetic anisotropy in martensitic Ni2MnGa
2011
The microscopic origin of magnetic anisotropy in the shape memory alloy Ni${}_{2}$MnGa is investigated by means of x-ray magnetic circular dichroism in transmission mode. Field- and angle-dependent dichroism spectra of epitaxial Ni${}_{2}$MnGa(101)/MgO(001) films reveal pronounced differences for magnetization aligned parallel and perpendicular to the film plane. These differences are related to an anisotropy of the orbital magnetic moment in agreement with the observed out-of-plane magnetocrystalline anisotropy. The spectral variation of the x-ray absorption originates from changes in the spin-projected density of states when the magnetization vector is rotated from the easy to the hard ma…
Properties of Co/sub 2/YZ Heusler compounds
2005
Heusler compounds of Co/sub 2/XY composition (Co/sub 2/Cr/sub 0.6/Fe/sub 0.4/Al, Co/sub 2/FeSi) offer a variety of half-metallic ferromagnetic materials. These were prepared by arc melting and comprehensively characterized by means of X-ray diffraction ( XRD), Mossbauer spectroscopy, magnetic X-ray circular dichroism spectroscopy (MXCD), superconducting quantum interference device (SQUID) magnetometry, electron spectroscopy for chemical analysis (ESCA), extended X-ray absorption fine structure (EXAFS) and Auger electron spectroscopy (AES) depth profiling. Structural disorder phenomena, magnetic hysteresis, magnetic moments, magnetic transition temperatures and Curie temperature were obtaine…
The Peculiar Physical Properties of Nanosized Ferroics (Nanoferroics)
2013
This Chapter contains the experimental facts about size effects in nanoferroics. They include ferroelectric, ferroelastic, magnetic and multiferroic nanostructured materials. The main peculiar feature of nanoferroics is the geometric confinement originating from their surfaces and interfaces. This is in contrast to the ordinary bulk ferroics, where the sample surface plays a minor role. In particular, in nanoferroics, the surface generates the physical properties gradients in the normal (to the surface) direction. This fact yields strong size effects and spatial inhomogeneity of the nanoferroics properties, which should be taken into account to get their adequate physical description. We re…
Magnetization states in ultrathin films with laterally modulated anisotropies
1998
Abstract Micromagnetic theory has been applied to a model system for ultrathin films with laterally modulated anisotropies, consisting of a periodic array of stripes with alternating uniaxial anisotropies. Despite of the discontinuous change of anisotropy, the magnetization direction only changes on a lateral scale given by the exchange length. If the width of one of the two alternating stripes is reduced below a critical value, the magnetization will switch into a uniform state. The variation of the critical width with period, anisotropy constants, exchange constant, and film thickness has been determined using an analytic approach. Non-uniform magnetization states and the magnetization re…
Magnetic Coupling in Y3Fe5O12/Gd3Fe5O12 Heterostructures
2021
Ferrimagnetic ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ (YIG) is the prototypical material for studying magnonic properties due to its exceptionally low damping. By substituting the yttrium with rare earth elements that have a net magnetic moment, we can introduce an additional spin degree of freedom. Here, we study the magnetic coupling in epitaxial ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$/${\mathrm{Gd}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ (YIG/GIG) heterostructures grown by pulsed laser deposition. From bulk sensitive magnetometry and surface sensitive spin Seebeck effect and spin Hall magnetoresistance measurements, we determine the alignment of the heterostruct…
Multiferroic BiFeO<inf>3</inf> for conductance control at the LaAlO<inf>3</inf>/SrTiO<inf>3</inf>-interface
2015
Multiferroic materials possessing both magnetic and ferroelectric order enable in principle to switch order parameters using not the direct reciprocal field, e.g. to switch the magnetization by an electric field or the electric polarization by a magnetic field. A recent breakthrough was achieved by the demonstration of the ferromagnetic switching of a Co layer with an electric field employing the multiferroic BiFeO 3 [1]. The latter material is a perovskite based oxide that shows stable ferro-electricity as well as an antiferromagnetic order at room temperature [2,3]. Due to a Dzyaloshinskii-Moriya interaction induced by rotation of oxygen octahedra leading to noncollinear Fe-O-Fe bonds a s…
Magnetic quantum criticality in quasi-one-dimensional Heisenberg antiferromagnet Cu (C4H4N2)( NO 3)2
2016
We analyze exciting recent measurements [Phys. Rev. Lett. 114 (2015) 037202] of the magnetization, differential susceptibility and specific heat on one dimensional Heisenberg antiferromagnet Cu(C4H4N2)(NO3)2 (CuPzN) subjected to strong magnetic fields. Using the mapping between magnons (bosons) in CuPzN and fermions, we demonstrate that magnetic field tunes the insulator towards quantum critical point related to so-called fermion condensation quantum phase transition (FCQPT) at which the resulting fermion effective mass diverges kinematically. We show that the FCQPT concept permits to reveal the scaling behavior of thermodynamic characteristics, describe the experimental results quantitativ…
Rational design of a new class of heterobimetallic molecule-based magnets: Synthesis, crystal structures, and magnetic properties of oxamato-bridged …
2008
Abstract Two new series of oxamato-bridged heterobimetallic coordination networks of general formula Li5[Li3M2(mpba)3(H2O)6] · 31H2O [M = NiII (1a) and CoII (1b)] and Li2[Mn3M2(mpba)3(H2O)6] · 22H2O [M = NiII (2a) and CoII (2b)] have been prepared from the metal-mediated self-assembly of the hexakis(bidentate), triple-stranded dinickel(II) and dicobalt(II) complexes [M2(mpba)3]8− [mpba = meta-phenylenebis(oxamato)] with either monovalent lithium(I) or divalent manganese(II) ions respectively, in water. X-ray structural analyses of 1a and 1b show an anionic three-dimensional network formed by an infinite parallel array of oxamato-bridged Li 3 I M 2 II (M = Ni and Co) hexagonal layers, which …