Search results for "Curie temperature"
showing 10 items of 68 documents
Structural, electronic, and magnetic properties of pseudomorphic CrFe nanostripes on W(110)
2007
We have grown pseudomorphic binary ${\mathrm{Cr}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}$ alloy monolayers and sequences of Cr and Fe nanostripes on W(110) by molecular-beam epitaxy in ultrahigh vacuum. By coadsorption of Cr and Fe a pseudomorphic random CrFe alloy grows on the W(110) substrate. At a substrate temperature of $700\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ the CrFe alloy forms monolayer stripes in the step flow growth mode. We have measured magnetic properties of the monolayer alloy for $0.75\ensuremath{\leqslant}x\ensuremath{\leqslant}1$ using Kerr magnetometry. At a constant relative temperature $t=T∕{T}_{C}$ the saturation value of the Kerr rotation shows a maximum at $x=0.95$ an…
Effect of zinc concentration on the microstructure and relaxation frequency of Mn–Zn ferrites synthesized by solid state reaction
2013
Abstract Mn3Zn polycrystalline ferrites with Mn1−xZnxFe2O4 stoichiometry (x=0.59, 0.61, 0.65) were prepared by solid state reaction. These ferrites were heated at different temperatures. The cubic structure with space group Fd3m (Oh7) No. 227 was confirmed by the refinement of x-ray diffraction (XRD) powders through Rietveld´s method using fullprof. Scanning electron microscopy (SEM) results revealed for all compounds a non-homogeneous grain size and shape distribution, with a mean grain size of 9 μm. The Curie temperature Tc was found to decrease as the Zn concentration increases. The magnetic domain relaxation was investigated by inductance spectroscopy (IS). The relaxation frequency fr s…
Epitaxial films of the magnetic shape memory material
2007
Abstract By DC-sputtering from a stoichiometric target onto sapphire substrates we prepared epitaxial films of Ni 2 MnGa . X-ray diffraction in two circle geometry shows only the Ni 2 MnGa peaks corresponding to a (1 1 0) oriented growth on the (1 1 0) oriented sapphire substrate. Rocking curve scans shows that the out of plane orientation has a width of only 1 . 1 ∘ . By four circle X-ray diffraction we find an in-plane aligned growth. The Curie temperature as determined by SQUID magnetometry is 368 K. On cooling down the low field magnetization drops at around 260–280 K indicating the austenite to martensite transition. The presence of two different phases at high and low temperature also…
Large magnetoresistance at room temperature in the off-stochiometric chalcogenide Cr0.92Te
2006
Abstract We present the electronic and magnetic properties of the transition chalcogenide Cr0.92Te. The compound is the hexagonal counterpart to the hypothetical half-metallic ferromagnet CrTe. The off-stochiometric phase crystallizes in the hexagonal NiAs-type structure P63/mmm. New magnetotransport results show a large magnetoresistance (MR) of 5.5% at room temperature in a magnetic field of 8 T. The remarkable MR-effect can be explained with spin-dependent scattering below the Curie temperature.
Domain wall transformations and hopping in La0.7Sr0.3MnO3nanostructures imaged with high resolution x-ray magnetic microscopy
2014
We investigate the effect of electric current pulse injection on domain walls in La(0.7)Sr(0.3)MnO(3) (LSMO) half-ring nanostructures by high resolution x-ray magnetic microscopy at room temperature. Due to the easily accessible Curie temperature of LSMO, we can employ reasonable current densities to induce the Joule heating necessary to observe effects such as hopping of the domain walls between different pinning sites and nucleation/annihilation events. Such effects are the dominant features close to the Curie temperature, while spin torque is found to play a small role close to room temperature. We are also able to observe thermally activated domain wall transformations and we find that,…
Temperature-dependent magnetic anisotropy in the layered magnetic semiconductors CrI3 and CrBr3
2018
Chromium trihalides are layered and exfoliable semiconductors and exhibit unusual magnetic properties with a surprising temperature dependence of the magnetization. By analyzing the evolution of the magnetocrystalline anisotropy with temperature in chromium iodide $\mathrm{Cr}{\mathrm{I}}_{3}$, we find it strongly changes from ${K}_{u}=300\ifmmode\pm\else\textpm\fi{}50\phantom{\rule{4pt}{0ex}}\mathrm{kJ}/{\mathrm{m}}^{3}$ at $5\phantom{\rule{4pt}{0ex}}\mathrm{K}$ to ${K}_{u}=43\ifmmode\pm\else\textpm\fi{}7\phantom{\rule{4pt}{0ex}}\mathrm{kJ}/{\mathrm{m}}^{3}$ at $60\phantom{\rule{4pt}{0ex}}\mathrm{K}$, close to the Curie temperature. We draw a direct comparison to $\mathrm{CrB}{\mathrm{r}}_…
Composition-related structural, thermal and mechanical properties of Ba1−xSrxTiO3ceramics (0 ≤x≤ 0.4)
2015
The Ba1−xSrxTiO3 (BST) ceramics were prepared by conventional ceramic method. The crystalline structure and morphology were studied by X-ray diffraction and scanning electron microscopy, respectively. Experimental results show that increase of sintering temperature leads to an uncontrolled precipitating of the phase with a lower content of Ti. The dielectric constant and specific heat as a function of composition and temperature were investigated. The increasing concentration of Sr ions leads to a shift of the Curie point below room temperature. To determine the elastic constants (the Young's modulus E, the shear modulus G and the Poisson's ratio v) of BST, a method of measurement of the lo…
Substitution Effects in Double Perovskites: How the Crystal Structure Influences the Electronic Properties
2013
We systematically studied substituted Sr2FeReO6 with respect to experimental characterization and theoretical band structure calculations. In the framework of the tight-binding approach, hole- or electron-doping of Sr2MM’O6 were performed at the M or M’ positions either by transition or main group metals. Hole-doping, rather than electron-doping, has a favorable effect to improve the half-metallicity (Curie temperature and saturation magnetization) of the parent compound. When M is substituted by another metal, the original M’ metal will serve as a redox buffer (and vice versa). Substituting M by another metal with a size similar to that of the metal at M’ position causes disorder, which ha…
Control of Oxygen Nonstoichiometry and Magnetic Property of MnCo2O4 Thin Films Grown by Atomic Layer Deposition
2010
Spinel-structured (Mn,Co)3O4 thin films were reproducibly fabricated by atomic layer deposition (ALD) using Mn(thd)3, Co(thd)2, and ozone as precursors. A full control of the cation ratio was achieved in the temperature interval 140−160 °C within which also the growth rate remained constant. Precise control of the oxygen content of as-deposited MnCo2O4+δ films was achieved through postdeposition heat treatments at prefixed temperatures in air and N2 atmospheres, as evidenced from the monotonous increases of both the unit cell volume and the Curie temperature (TC) with increasing annealing temperature/decreasing oxygen partial pressure. The TC value varied from 92 K for the as-deposited MnCo…
Crystal chemical and dielectric properties of Pb0.5(5-x)LaxNb5-xFexO15system with “tetragonal tungsten bronze” structural type
2005
The lanthanum-lead and iron-niobium coupled substitution in PbNb 2 O 6 have allowed to isolate new materials of a general formula Pb 0.5(5-x) La x Nb 5-x Fe x O 15 crystallising with the tetragonal tungsten bronze structural type. The resulting influence on the lattice parameters, the ferroelectric Curie temperature and Cole - Cole plots are presented. A typical ferroelectric - paraelectric behaviour occurs in the composition range 0 ≤ x ≤ 0.33 while, a relaxor behaviour is observed in the composition range 0.33 < x < 1.