R. K. Rakshit

Origin of ‘in-plane’ and ‘out-of-plane’ magnetic anisotropies in as-deposited and annealed CoFeB ferromagnetic thin films

A detailed comparative Ferromagnetic resonance study of pulsed laser deposited Co40Fe40B20 thin films, before and after annealing, was under taken. The dependence of resonance field (Hres) and peak-to-peak linewidth (ΔHpp) on film thickness, annealing temperature, and magnetic field orientation is examined. ‘In-plane’ (IP) and ‘out-of-plane’ (OP) angular dependence of the resonance fields, (IP:Hres(ψ); OP:Hres(α)), were measured at T = 150 and 295 K for the as deposited (as-) to annealed (an-) thin film samples to determine IP (HK∥) and OP (HK⊥) uniaxial anisotropy fields. Variation of Hres(ψ) and Hres(α) on sample geometry demonstrate that the uniaxial magnetic anisotropy is present in as- and an-thin films of Co40Fe40B20. The effective magnetic anisotropy (Kueff) increases after nanocrystallization in CoFeB films indicates that the exchange interactions are unable to average out the local-magnetocrystalline anisotropy of the nanocrystalline grains and thereby lead to magnetic hardening in the early stag...

Effect of thermal annealing on Boron diffusion, micro-structural, electrical and magnetic properties of laser ablated CoFeB thin films

We report on Boron diffusion and subsequent crystallization of Co40Fe40B20 (CoFeB) thin films on SiO2/Si(001) substrate using pulsed laser deposition. Secondary ion mass spectroscopy reveals Boron diffusion at the interface in both amorphous and crystalline phase of CoFeB. High-resolution transmission electron microscopy reveals a small fraction of nano-crystallites embedded in the amorphous matrix of CoFeB. However, annealing at 400°C results in crystallization of CoFe with bcc structure along (110) orientation. As-deposited films are non-metallic in nature with the coercivity (Hc) of 5Oe while the films annealed at 400°C are metallic with a Hc of 135Oe.

Correlation of current–voltage–temperature analysis with deep level defects in epitaxial GaN films

The effect of temperature on the nature of metal-semiconductor system in a Au contact deposited on c-plane and a-plane GaN film was investigated by current–voltage (I–V) measurements. The I–V measurements have been obtained systematically at different temperatures ranging from room temperature (300 K) to low temperature (78 K). Photoluminescence measurements were obtained to investigate correlation between the growth conditions, the substrate used for the growth of GaN film, and the presence of deep level defects therein by equating with the yellow band luminescence. The resistance–voltage–temperature analysis indicates that a gradual shift of the nature of contact towards Schottky behavior takes place while moving from room temperature to low temperature. Additionally, memory effect like aberration is present at low temperature, which can be attributed to the presence of deep-level defects and carrier recombination therein.

Tunneling current in magnetic-ferroelectric-superconducting heterostructures

We report the tunneling current behavior of magnetic-ferroelectric-superconducting heterostructures for multistates non-volatile random access memory (NVRAM) elements. A heterostructure of La 0.67 Sr 0.33 MnO 3 (LSMO) (50 nm)/PbZr 0.52 Ti 0.48 O 3 (PZT) (5 nm)/Bi-Sr-Ca-Cu 2 -O X (BSCCO) (100 nm)/LaAlO 3 (LAO) architecture was fabricated by pulsed laser deposition technique. The tunneling effects were investigated well above and below the superconducting phase transition temperature of the BSCCO bottom electrode. A divergent current and conductance paths were observed for polarization up and down direction above the coercive field of the ferroelectric tunnel barrier. This behaviour was significant below T s where the moderate effect of the external magnetic field was also observed on the tunneling current. The dynamic conductance G ( V ) data fitted well with Brinkmans model for both polarizations up and polarization down states which suggest the presence of large tunnel electro-resistance.

Resistance minimum and electrical conduction mechanism in polycrystalline CoFeB thin films

The temperature dependent resistance

Dual anisotropic character in Fe/Pt multilayer grown on (001) MgO substrate

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Structural and electrical transport studies on CrN(001) thin films

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High yield strength bulk Ti based bimodal ultrafine eutectic composites with enhanced plasticity

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Wet chemical etching induced stress relaxed nanostructures on polar & non-polar epitaxial GaN films

) of polycrystalline ferromagnetic CoFeB thin films of varying thickness are analyzed considering various electrical scattering processes. We observe a resistance minimum in

Griffiths phase and critical behavior in layered Sr

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