Spin Reorientations Induced by Morphology Changes in Fe/Ag(001)

By means of magneto-optical Kerr effect we observe spin reorientations from in-plane to out-of-plane and vice versa upon annealing thin Fe films on Ag(001) at increasing temperatures. Scanning tunneling microscopy images of the different Fe films are used to quantify the surface roughness. The observed spin reorientations can be explained with the experimentally acquired roughness parameters by taking into account the effect of roughness on both the magnetic dipolar and the magnetocrystalline anisotropy.Comment: 4 pages with 3 EPS figure

Multistate current-induced magnetization switching in Au/Fe/MgO(001) epitaxial heterostructures

Magnetization switching using in-plane charge current recently has been widely investigated in heavy metal/ferromagnet bilayers with the switching mechanism usually attributed to the action of the spin-orbit coupling. Here we study in-plane current induced magnetization switching in model epitaxial bilayers that consist of Au(001) and Fe(001) grown on MgO(001). We use the planar Hall effect combined with magnetooptical Kerr effect (MOKE) microscopy to investigate magnetic properties of the bilayers and current-induced switching. We show that a current density beyond 1.4×107 A/cm can be employed for reproducible electrical switching of the magnetization between multiple stable states that correspond to different arrangements of magnetic domains with magnetization direction along one of the in-plane easy magnetization axes of the Fe(001) film. Lower current densities result in stable intermediate transversal resistances which are interpreted based on MOKE-microscopy investigations as resulting from the current-induced magnetic domain structure that is formed in the area of the Hall cross. We find that the physical mechanism of the current-induced magnetization switching of the Au/Fe/MgO(001) system at room temperature can be fully explained by the Oersted field, which is generated by the charge current flowing mostly through the Au layer

Multistate Current-Induced Magnetization Switching in Au/Fe/MgO(001) Epitaxial Heterostructures

Magnetization switching using in-plane charge current recently has been widely investigated in heavy metal/ferromagnet bilayers with the switching mechanism usually attributed to the action of the spin-orbit coupling. Here we study in-plane current induced magnetization switching in model epitaxial bilayers that consist of Au(001) and Fe(001) grown on MgO(001). We use the planar Hall effect combined with magnetooptical Kerr effect (MOKE) microscopy to investigate magnetic properties of the bilayers and current-induced switching. We show that a current density beyond 1.4×107 A/cm2 can be employed for reproducible electrical switching of the magnetization between multiple stable states that correspond to different arrangements of magnetic domains with magnetization direction along one of the in-plane easy magnetization axes of the Fe(001) film. Lower current densities result in stable intermediate transversal resistances which are interpreted based on MOKE-microscopy investigations as resulting from the current-induced magnetic domain structure that is formed in the area of the Hall cross. We find that the physical mechanism of the current-induced magnetization switching of the Au/Fe/MgO(001) system at room temperature can be fully explained by the Oersted field, which is generated by the charge current flowing mostly through the Au layer. © 2021 authors. Published by the American Physical Society

Diesel injector dynamic modelling and estimation of injection parameters from impact response Part 1: modelling and analysis of injector impacts

Part 1 of this paper presents the development and validation of a detailed dynamic model for the needle motion of a common hole‐type diesel fuel injector as used in a direct injection diesel engine. The injector needle motion is described as a two‐mass piece‐wise linear vibro‐impact system, unlike the conventional modelling techniques which use a single‐mass approach. The use of two masses permits analysis of both the needle impact behaviour and of the more general dynamics of the fuel injection process. Model parameters are derived from a combination of measurement and estimation, and the subsequent model is evaluated via direct measurement of the spring seat displacement. The opening and closing needle impact behaviour is shown to exhibit close correlation with key injection parameters, including fuel injection pressure, fuelling rate and timing. The model revealed that the impact of the needle when opening is found to exhibit lower amplitude but more high‐frequency components than the impact associated with the closing. The measurement of the injector body vibration response to these impacts is shown to enable non‐intrusive estimation of injection parameters, alleviating the problems associated with conventional intrusive needle‐lift measurement. Table 1 caption: Injector specifications Fig. 1 caption: Schematic and dynamic model of an injector valve Fig. 2 caption: Comparison between measurement and predicted needle lift Fig. 3 caption: Injection speed behaviours at a fuelling of 35 mm3/injection Fig. 4 caption: Injection fuel behaviours at a speed of setting 1.0 m/s Fig. 5 caption: Impact/speed correlation at a fuelling of 35 mm3/injection Fig. 6 caption: Time‐frequency analysis of injector impacts Fig. 7 caption: Correlation between fuel injection parameters and impacts Fig. 8 caption: Influence of needle mass on fuel injectio

Iron silicide formation at different layers of (Fe/Si)3 multilayered structures determined by conversion electron Mössbauer spectroscopy

Under the terms of the Creative Commons Attribution 3.0 Unported License to their work.The morphology and the quantitative composition of the Fe-Si interface layer forming at each Fe layer of a (Fe/Si)3 multilayer have been determined by means of conversion electron Mössbauer spectroscopy (CEMS) and high-resolution transmission electron microscopy (HRTEM). For the CEMS measurements, each layer was selected by depositing the Mössbauer active 57Fe isotope with 95% enrichment. Samples with Fe layers of nominal thickness dFe  = 2.6 nm and Si spacers of dSi  = 1.5 nm were prepared by thermal evaporation onto a GaAs(001) substrate with an intermediate Ag(001) buffer layer. HRTEM images showed that Si layers grow amorphous and the epitaxial growth of the Fe is good only for the first deposited layer. The CEMS spectra show that at all Fe/Si and Si/Fe interfaces a paramagnetic c-Fe1− x Si phase is formed, which contains 16% of the nominal Fe deposited in the Fe layer. The bottom Fe layer, which is in contact with the Ag buffer, also contains α-Fe and an Fe1− x Si x alloy that cannot be attributed to a single phase. In contrast, the other two layers only comprise an Fe1− x Si x alloy with a Si concentration of ≃0.15, but no α-Fe.The financial support of the Spanish MINECO MAT2011- 23791, the Aragonese DGA-IMANA E34 (co-funded by Fondo Social Europeo) and that received from the European Union FEDER funds is acknowledged. L.B.-R. acknowledges the Spanish MINECO FPU 2010 grant.Peer Reviewe

Tunneling in epitaxial Fe/Si/Fe structures with strong antiferromagnetic interlayer coupling

Fe(5 nm)/Si(0.8-2 nm)/Fe(5 nm) structures are grown by molecular-beam epitaxy on Ag(001) buffered GaAs substrates. Ferromagnetic tunneling junctions with crossed electrodes and junction areas ranging from 22 to 225 mum(2) are patterned using photolithography. Antiparallel alignment of the magnetizations due to antiferromagnetic interlayer coupling, which is confirmed by longitudinal magneto-optical Kerr effect hysteresis loops, exists for the whole range of spacer thicknesses. Transport properties in current perpendicular to the sample plane geometry are examined by the four-point method in the temperature range from 4 K to room temperature. As a function of spacer thickness, the junctions show a strong increase of the resistance times area product from approximate to1 Omega mum(2) to more than 10 kOmega mum(2). The dI/dV-V curves are parabolic and asymmetric and thus characteristic for trapezoidal tunneling barriers. The mean barrier heights derived from Brinkman fits range from 0.3 to 0.8 eV. The zero-bias resistance of the tunneling junctions moderately decreases with temperature by less than 10% over the whole measured temperature range. All these transport properties fulfill the necessary and sufficient criteria for elastic tunneling. (C) 2003 American Institute of Physics