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Claas Abert - One of the best experts on this subject based on the ideXlab platform.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    Applied Physics Letters, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in magnetic random access memory cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. In this paper, it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use of a dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and another layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    arXiv: Computational Physics, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in MRAM cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. Within this paper it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use a of dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and a second layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

Dieter Suess - One of the best experts on this subject based on the ideXlab platform.

  • Effective uniaxial Anisotropy in easy-plane materials through nanostructuring
    Applied Physics Letters, 2017
    Co-Authors: Johann Fischbacher, Dieter Suess, Alexander Kovacs, Harald Oezelt, Markus Gusenbauer, Thomas Schrefl
    Abstract:

    Permanent magnet materials require a high uniaxial magneto-Crystalline Anisotropy. Exchange coupling between small crystallites with easy-plane Anisotropy induces an effective uniaxial Anisotropy if arranged accordingly. Nanostructuring of materials with easy-plane Anisotropy is an alternative way to create hard-magnetic materials. The coercivity increases with decreasing feature size. The resulting coercive field is about 12 percent of the Anisotropy field for a crystal size of 3.4 times the Bloch parameter.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    Applied Physics Letters, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in magnetic random access memory cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. In this paper, it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use of a dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and another layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    arXiv: Computational Physics, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in MRAM cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. Within this paper it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use a of dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and a second layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

Farshid Sadeghi - One of the best experts on this subject based on the ideXlab platform.

  • a method to model Crystalline Anisotropy in contact using semi analytical method
    Tribology International, 2020
    Co-Authors: Thibault Beyer, Farshid Sadeghi, Thibaut Chaise, Julien Leroux, Daniel Nelias
    Abstract:

    Abstract In this paper, the contact problem between a cylinder and a half-space with a Crystalline anisotropic behavior is solved. The model is based on semi-analytical methods to solve a three dimensional contact problem. A numerical technique based on a Voronoi tessellation is implemented using the Eshelby's equivalent inclusion method to account for the effect of the material microstructure on the contact pressure distribution and subsurface stresses. Fast Fourier Transforms (3D and 2D) are used to reduce the computation cost of the simulations. An application of this method to compute the scatter in fatigue life of rolling element bearings is also presented. Three different critical stresses are used in the Lundberg-Palmgren equation and results are compared in term of Weibull plot slope.

  • A continuum damage mechanics framework for modeling the effect of Crystalline Anisotropy on rolling contact fatigue
    Tribology International, 2019
    Co-Authors: Akhil Vijay, Farshid Sadeghi
    Abstract:

    Abstract Rolling contact fatigue (RCF) is the primary mode of fatigue failure in well-lubricated rolling element bearings. Typical fatigue failures in bearings are characterized by microcrack formation (initiation phase), which then coalesce to a large crack that grows to the surface (propagation phase). Hence, RCF is a micromechanical phenomenon driven by microstructural inhomogeneity. This paper presents a coupled damage mechanics - cohesive element method (DM-CEM) to model crack initiation and propagation in polyCrystalline material aggregates subject to RCF loading. The material microstructural topology is represented using Voronoi tessellations. The grain boundaries are modeled using cohesive elements. Each grain is composed of cubic anisotropic material and is randomly oriented in material space. A quasi-static Hertzian pressure profile is passed over the surface to simulate a bearing race under dynamic loading. Damage is initiated at the grain boundaries by degradation of the cohesive elements and the rate of damage/degradation is used to characterize the fatigue life evolution. The resulting final spall patterns and fatigue life scatter corroborate well with existing results from open literature. The model was extended and used to demonstrate the feasibility of the Fatemi - Socie criterion as a possible approach for estimating RCF life.

  • a 3d finite element modelling of Crystalline Anisotropy in rolling contact fatigue
    International Journal of Fatigue, 2018
    Co-Authors: Akhil Vijay, Neil R Paulson, Farshid Sadeghi
    Abstract:

    Abstract Rolling contact fatigue (RCF) is one of the primary modes of failure in bearings and in this study it is hypothesized and demonstrated that RCF is strongly influenced by inhomogeneity in polyCrystalline material microstructure. This paper presents a three-dimensional modeling approach to include the effects of microstructure topology and material Anisotropy in a polyCrystalline microstructural bearing steel subject to RCF loading. A randomly generated 3D Voronoi tessellation is used to represent the microstructural topology of the material. A cubic material definition with random spatial orientation is specified for the material grains to simulate the polyCrystalline Anisotropy. The size of the RVE was chosen such that it represented the macroscopic linear elastic material properties of a polyCrystalline aggregate. The semi-infinite domain is then subjected to a moving Hertzian pressure to simulate a load cycle. Due to inhomogeneity in the polyCrystalline material local stress risers occur at the grain boundaries, however, in general, the locations of the maximum shear stresses compare well to the experimental RCF results readily available in literature. Elemental shear stresses averaging scheme was employed to illustrate that the finite element model is mesh independent. The estimated fatigue life scatter obtained from the inhomogeneous polyCrystalline material model corroborates well with the fatigue life scatter obtained from the RCF experiments.

Christoph Vogler - One of the best experts on this subject based on the ideXlab platform.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    Applied Physics Letters, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in magnetic random access memory cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. In this paper, it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use of a dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and another layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    arXiv: Computational Physics, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in MRAM cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. Within this paper it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use a of dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and a second layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

Florian Bruckner - One of the best experts on this subject based on the ideXlab platform.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    Applied Physics Letters, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in magnetic random access memory cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. In this paper, it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use of a dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and another layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.

  • significant reduction of critical currents in mram designs using dual free layer with perpendicular and in plane Anisotropy
    arXiv: Computational Physics, 2017
    Co-Authors: Dieter Suess, Christoph Vogler, Florian Bruckner, H Sepehriamin, Claas Abert
    Abstract:

    One essential feature in MRAM cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. Within this paper it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use a of dual free layer device, which consists of one layer with perpendicular Crystalline Anisotropy and a second layer with in-plane Crystalline Anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.