Jitendra Pal Singh; Sanjeev Gautam; Braj Bhusan Singh; Sujeet Chaudhary; D. Kabiraj; D. Kanjilal; K. H. Chae; R. Kotnala; Jenn-Min Lee; Jin-Ming Chen; K. Asokan
Abstract
MgO based magnetic tunnel junctions (MTJs) exhibit high tunneling magnetoresistance (TMR) and have potential applications in magnetic random access memories. This study addresses the role of interface in the Fe/MgO/Fe based MTJs. For present investigation, Fe/MgO/Fe multilayer stack on Si substrates ...
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MgO based magnetic tunnel junctions (MTJs) exhibit high tunneling magnetoresistance (TMR) and have potential applications in magnetic random access memories. This study addresses the role of interface in the Fe/MgO/Fe based MTJs. For present investigation, Fe/MgO/Fe multilayer stack on Si substrates is grown by electron beam evaporation method and has been investigated for structural, magnetic and electronic properties. All the layers in the stack were of polycrystalline in nature as evidenced from X-ray diffraction studies, and the magnetic measurements show the attributes perpendicular magnetic anisotropy. Results from near edge X-ray absorption spectra at Fe L-edges measured by total electron yield mode and X-ray reflectometry indicate the formation of FeOx at the Fe/MgO interface. These are associated with hybridization of Fe (3d)-O(2p) levels at Fe/MgO interface in the stack and thickness of layers in the stacks. Absence of magnetic de-coupling between top and bottom ferromagnetic layers has been attributed to interface roughness and oxidation at Fe/MgO interface. This study highlights the role of interface and oxidation that need to be considered for improving the TMR for devices.
Hardeep Kumar; L. Olivi;G. Aquilanti; S. Ghosh; P. Srivastava; D. Kabiraj; D. K. Avasthi
Abstract
A series of FeCo-SiO2 granular films of different FeCo atomic concentration (33-54%) have been prepared by fast atom beam sputtering technique and post-annealed in inert (Ar) and reducing (H2) gas environments. Fe and Co K-edge XANES analysis of as-deposited films indicate that both Fe and Co are present ...
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A series of FeCo-SiO2 granular films of different FeCo atomic concentration (33-54%) have been prepared by fast atom beam sputtering technique and post-annealed in inert (Ar) and reducing (H2) gas environments. Fe and Co K-edge XANES analysis of as-deposited films indicate that both Fe and Co are present mainly in their elemental (Fe 0 , Co 0 ) state. A partial oxidation of Fe and Co is observed, as the FeCo alloy content decreases (54 to 33%) due to reduced particle size. XANES/XAFS analysis shows the formation of FeCo alloy with bcc Fe structure in H2 environment annealed films. The XRD and Raman analysis of Ar environment annealed films suggest the formation of Co3O4 and CoFe2O4 phases. The Ar environment is found not to be effective reducing medium to stabilize the FeCo alloy phase, while H2 environment annealing (450-700 o C) leads to formation of bcc FeCo alloy.
Indra Sulania; Ambuj Tripathi; D. Kabiraj; Matthieu Lequeux; Devesh Avasthi
Abstract
In the present study, Indium Phosphide (InP) (100) samples with a thickness of ~ 0.5 mm have been bombarded with 1.5 keV Argon atoms for a fixed fluence of 8 × 10 16 atoms/cm 2 . The angle of incidence of the atom beam has been varied from normal incidence to 76° with respect to surface normal. ...
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In the present study, Indium Phosphide (InP) (100) samples with a thickness of ~ 0.5 mm have been bombarded with 1.5 keV Argon atoms for a fixed fluence of 8 × 10 16 atoms/cm 2 . The angle of incidence of the atom beam has been varied from normal incidence to 76° with respect to surface normal. The bombarded surface shows the nanostructures as analysed by Atomic Force Microscopy (AFM). For normal and near normal incident angles of the beam, nanodots pattern have been observed and after a critical angle of incidence, the dots begin to align and with further increase of angle, nanostructures elongate along the beam direction. At 63° incidence, a well ordered ripple pattern has been reported. The evolution of nanostructures from nanodots to nanoripples has been analysed in terms of their size, shape and roughness by means of AFM imaging.
