The Experts below are selected from a list of 32346 Experts worldwide ranked by ideXlab platform
D S Schmool - One of the best experts on this subject based on the ideXlab platform.
-
spin configurations in Hard soft coupled biLayer systems transitions from rigid magnet to exchange spring
2010Co-Authors: N De Sousa, A Apolinario, F Vernay, Pedro Monteiro, F Albertini, F Casoli, H Kachkachi, D S SchmoolAbstract:We investigate equilibrium properties of an exchange-spring magnetic system constituted of a soft Layer (e.g., Fe) of a given thickness on top of a Hard magnetic Layer (e.g., FePt). The magnetization profile $M(z)$ as a function of the atomic position ranging from the bottom of the Hard Layer to the top of the soft Layer is obtained in two cases with regard to the Hard Layer: (i) in the case of a rigid interface (the FePt Layer is a single Layer), the profile is obtained analytically as the exact solution of a sine-Gordon equation with Cauchy's boundary conditions. Additional numerical simulations also confirm this result. Asymptotic expressions of $M(z)$ show a linear behavior near the bottom and the top of the soft Layer. In addition, a critical value of the number of atomic planes in the soft Layer, that is necessary for the onset of spin deviations, is obtained in terms of the anisotropy and exchange coupling between the adjacent plane in the soft Layer. (ii) In the case of a relaxed interface (the FePt Layer is a multiLayer), the magnetization profile is obtained numerically for various Fe and FePt films thicknesses and applied field.
-
magnetization dynamics in exchange coupled spring systems with perpendicular anisotropy
2010Co-Authors: Pedro Monteiro, D S SchmoolAbstract:Magnetization dynamics in exchange spring magnets have been studied using simulations of the FePt/Fe biLayer system. The FePt Hard Layer exhibits strong perpendicular magnetocrystalline anisotropy while the soft (Fe) Layer has negligible magnetocrystalline anisotropy. The variation in the local spin orientation in the Fe Layer is determined by the competition of the exchange coupling interaction with the Hard Layer and the magnetostatic energy which favors in-plane magnetization. Dynamics were studied by monitoring the response of the Fe Layer magnetization after the abrupt application of a magnetic field which causes the systems to realign via precessional motion. This precessional motion allows us to obtain the frequency spectrum and hence examine the dynamical magnetization motion. Since the rotation of the spins in the soft Layer does not have a well-defined magnetic anisotropy, the system does not present the usual frequency field characteristics for a thin film. Additionally we obtain multipeaked resonance spectra for the application of magnetic fields perpendicular to the film plane, though we discount the existence of spin-wave modes and propose that this arises due to variations in the local effective field across the Fe Layer. The dynamic response is only considered in the Fe Layer, with the FePt Layer held fixed in the perpendicular orientation.
F Casoli - One of the best experts on this subject based on the ideXlab platform.
-
spin configurations in Hard soft coupled biLayer systems transitions from rigid magnet to exchange spring
2010Co-Authors: N De Sousa, A Apolinario, F Vernay, Pedro Monteiro, F Albertini, F Casoli, H Kachkachi, D S SchmoolAbstract:We investigate equilibrium properties of an exchange-spring magnetic system constituted of a soft Layer (e.g., Fe) of a given thickness on top of a Hard magnetic Layer (e.g., FePt). The magnetization profile $M(z)$ as a function of the atomic position ranging from the bottom of the Hard Layer to the top of the soft Layer is obtained in two cases with regard to the Hard Layer: (i) in the case of a rigid interface (the FePt Layer is a single Layer), the profile is obtained analytically as the exact solution of a sine-Gordon equation with Cauchy's boundary conditions. Additional numerical simulations also confirm this result. Asymptotic expressions of $M(z)$ show a linear behavior near the bottom and the top of the soft Layer. In addition, a critical value of the number of atomic planes in the soft Layer, that is necessary for the onset of spin deviations, is obtained in terms of the anisotropy and exchange coupling between the adjacent plane in the soft Layer. (ii) In the case of a relaxed interface (the FePt Layer is a multiLayer), the magnetization profile is obtained numerically for various Fe and FePt films thicknesses and applied field.
-
strong coercivity reduction in perpendicular fept fe biLayers due to Hard soft coupling
2008Co-Authors: F Casoli, F Albertini, L Nasi, S Fabbrici, Riccardo Cabassi, F Bolzoni, C BocchiAbstract:We have prepared perpendicular Hard/soft biLayers made of a 10nm L10-FePt Layer, which has been epitaxially grown on MgO(100) and a Fe Layer with thicknesses of 2 and 3.5nm. The control of the interface morphology allows to modify the magnetic regime at fixed Fe thickness (from rigid magnet to exchange-spring magnet), due to the nanoscale structure effect on the Hard/soft coupling and to tailor the hysteresis loop characteristics. Despite the small thickness of the soft Layer, the coercivity is strongly reduced compared to the Hard Layer value, indicating that high anisotropy perpendicular systems with moderate coercivity can be easily obtained.
Jun Wang - One of the best experts on this subject based on the ideXlab platform.
-
thermal stability of low temperature carburized austenitic stainless steel
2017Co-Authors: Jun Wang, Zhen Li, Danqi Wang, F ErnstAbstract:Abstract To study the thermal stability of the “case” (Hard Layer) that forms on AISI-316L austenitic stainless steel by low-temperature carburization, we exposed carburized specimens to temperatures between 573 K and 648 K (300 and 375 °C) in air for 20.7 Ms (8 months). In spite of a colossal supersaturation with carbon, the austenite does not precipitate carbides. No carbon is lost to the ambient. Carbon diffuses deeper into the alloy, resulting in a flatter carbon-fraction–depth profile. This is realistically simulated assuming temperature- and concentration-dependent carbon diffusion. Exposing to 648 K for 20.7 Ms about doubles the average carbon depth. The near-surface carbon fraction decreases only moderately, particularly as the material appears to assimilate carbon from the ambient. Accordingly, the beneficial effects of low-temperature carburization on mechanical properties and corrosion resistance are retained throughout such long-term heat exposure, implying corresponding service life of low-temperature-carburized parts at temperatures below 650 K.
Pedro Monteiro - One of the best experts on this subject based on the ideXlab platform.
-
spin configurations in Hard soft coupled biLayer systems transitions from rigid magnet to exchange spring
2010Co-Authors: N De Sousa, A Apolinario, F Vernay, Pedro Monteiro, F Albertini, F Casoli, H Kachkachi, D S SchmoolAbstract:We investigate equilibrium properties of an exchange-spring magnetic system constituted of a soft Layer (e.g., Fe) of a given thickness on top of a Hard magnetic Layer (e.g., FePt). The magnetization profile $M(z)$ as a function of the atomic position ranging from the bottom of the Hard Layer to the top of the soft Layer is obtained in two cases with regard to the Hard Layer: (i) in the case of a rigid interface (the FePt Layer is a single Layer), the profile is obtained analytically as the exact solution of a sine-Gordon equation with Cauchy's boundary conditions. Additional numerical simulations also confirm this result. Asymptotic expressions of $M(z)$ show a linear behavior near the bottom and the top of the soft Layer. In addition, a critical value of the number of atomic planes in the soft Layer, that is necessary for the onset of spin deviations, is obtained in terms of the anisotropy and exchange coupling between the adjacent plane in the soft Layer. (ii) In the case of a relaxed interface (the FePt Layer is a multiLayer), the magnetization profile is obtained numerically for various Fe and FePt films thicknesses and applied field.
-
magnetization dynamics in exchange coupled spring systems with perpendicular anisotropy
2010Co-Authors: Pedro Monteiro, D S SchmoolAbstract:Magnetization dynamics in exchange spring magnets have been studied using simulations of the FePt/Fe biLayer system. The FePt Hard Layer exhibits strong perpendicular magnetocrystalline anisotropy while the soft (Fe) Layer has negligible magnetocrystalline anisotropy. The variation in the local spin orientation in the Fe Layer is determined by the competition of the exchange coupling interaction with the Hard Layer and the magnetostatic energy which favors in-plane magnetization. Dynamics were studied by monitoring the response of the Fe Layer magnetization after the abrupt application of a magnetic field which causes the systems to realign via precessional motion. This precessional motion allows us to obtain the frequency spectrum and hence examine the dynamical magnetization motion. Since the rotation of the spins in the soft Layer does not have a well-defined magnetic anisotropy, the system does not present the usual frequency field characteristics for a thin film. Additionally we obtain multipeaked resonance spectra for the application of magnetic fields perpendicular to the film plane, though we discount the existence of spin-wave modes and propose that this arises due to variations in the local effective field across the Fe Layer. The dynamic response is only considered in the Fe Layer, with the FePt Layer held fixed in the perpendicular orientation.
Kai Liu - One of the best experts on this subject based on the ideXlab platform.
-
anisotropy dependence of irreversible switching in fe smco and feni fept exchange spring magnet films
2005Co-Authors: J E Davies, Olav Hellwig, Eric E Fullerton, J S Jiang, S D Bader, Gergely T Zimanyi, Kai LiuAbstract:Magnetization reversal in exchange-spring magnet films has been investigated by a first-order reversal curve sFORCd technique and vector magnetometry. In Fe/epitaxial-SmCo films, the reversal proceeds by a reversible rotation of the Fe soft Layer, followed by an irreversible switching of the SmCo Hard Layer. The switching fields are clearly manifested by separate steps in both longitudinal and transverse hysteresis loops, as well as sharp boundaries in the FORC distribution. In FeNi/ polycrystalline-FePt films, particularly with thin FeNi, the switching fields are masked by the smooth and step-free major loop. However, the FORC diagram still displays a distinct onset of irreversible switching and transverse hysteresis loops exhibit a pair of peaks, whose amplitude is larger than the maximum possible contribution from the FeNi Layer alone. This suggests that the FeNi and FePt Layers reverse in a continuous process via a vertical spiral. The successive versus continuous rotation of the soft/Hard Layer system is primarily due to the different crystal structure of the Hard Layer, which results in different anisotropies. © 2005 American Institute of Physics . fDOI: 10.1063/1.1954898g
-
anisotropy dependence of irreversible switching in fe smco and feni fept exchange spring magnet films
2005Co-Authors: J E Davies, Olav Hellwig, Eric E Fullerton, J S Jiang, S D Bader, Gergely T Zimanyi, Kai LiuAbstract:Magnetization reversal in exchange-spring magnet films has been investigated by a First Order Reversal Curve (FORC) technique and vector magnetometry. In Fe/epitaxial-SmCo films, the reversal proceeds by a reversible rotation of the Fe soft Layer, followed by an irreversible switching of the SmCo Hard Layer. The switching fields are clearly manifested by separate steps in both longitudinal and transverse hysteresis loops, as well as sharp boundaries in the FORC distribution. In FeNi/polycrystalline-FePt films, particularly with thin FeNi, the switching fields are masked by the smooth and step-free major loop. However, the FORC diagram still displays a distinct onset of irreversible switching and transverse hysteresis loops exhibit a pair of peaks, whose amplitude is larger than the maximum possible contribution from the FeNi Layer alone. This suggests that the FeNi and FePt Layers reverse in a continuous process via a vertical spiral. The successive vs. continuous rotation of the soft/Hard Layer system is primarily due to the different crystal structure of the Hard Layer, which results in different anisotropies.
