The capacitance of MgO based magnetic tunnel junctions (MTJs) has been observed to be magnetic field dependent. We propose an equivalent circuit for the MTJs with a parallel-leaky

We study the effect of strain on magnetic tunnel junctions (MTJ) induced by a diamond like carbon (DLC) film. The junction resistance as well as the tunnel magnetoresistance (TMR) reduces with the DLC film. Non-equilibrium Green's function quantum transport calculations show that the application of biaxial strain increases the conductance for both the parallel and anti-parallel configurations. However, the conductance for the minority channel and for the antiparallel configuration is significantly more sensitive to strain, which drastically increases transmission through a MgO tunnel barrier, therefore, the TMR ratio decreases with biaxial strain. a)

Based on inspiration from an inverse optimization strategy and theoretical finite-difference time-domain method simulations, an ultralow loss power coupler between two different photonic crystal waveguides was designed, fabricated and characterized. The experimental results showed that the loss was less than 1 dB for transverse electric polarized light at a wavelength of 1550 nm, which is consistent with expectations from numerical modeling. High efficiency optical couplers are critical for development of integrated optical circuit functionality.

We propose a theoretical model of magnetic field dependence of hysteretic switching in magnetic granular system. The model is based on the self-trapped electrons mechanism. Our calculations show that the switching voltage may be significantly decreased with increasing the magnetic field. The underlying mechanism is the influence of the magnetic field on electron occupation of the conduction band, which depends on the materials used in magnetic granular system, concentration of magnetic granules in the insulating matrix, applied voltage, and the charge accumulation on the granules. We support our theoretical calculations by measuring the magnetic field dependence of resistive switching behaviour in Co/Al2O3 granular multilayers. Our experimental results are in qualitative agreement with the proposed theory

We study experimentally the effect of electric field on the magnetization of Co/Al 2 O 3 granular multilayers. We observe two distinct regimes: (a) low-field regime when the net magnetization of the system changes in a reversible way with the applied electric field and (b) high-field regime when the magnetization decreases irreversibly. The former is attributed to the changes in the relative 3d-orbital occupation of the minority and majority bands in the Co granules. A theoretical model has been developed to explain the electric field induced changes in the band structure of the granular system and hence the magnetic moment. The latter result may be understood assuming the electric field induces oxygen migration from Al 2 O 3 to the Co granules, since an increase in oxidation state of the Co granules is shown, through ab-initio calculations, to give rise to a reduced magnetization of the system. 2Electric field control of magnetism has aroused significant interest for future electronics as well as energy efficient magnetic data storage 1 . The effect of electric field on several electronic systems based on magnetic thin films has been demonstrated in the past few years.Application of an external electric field in perpendicular magnetic anisotropy based CoFeB/MgO/CoFeB magnetic tunnel junction aids in lowering the current densities for spin transfer torque switching 2 and for an ultra thin Fe film, the anisotropy direction can be controlled depending on the polarity of the electric field applied across the film. 3 Several theoretical reports also suggest the possibility of changes in the spin density of states at Fe/MgO interfaces in the presence of electric field that can affect both the anisotropy and the net moment of the Fe film. 4, 5Granular magnetic films provide interesting routes for novel physics and device applications by tailoring both the individual and collective properties of the nano-magnets. 6, 7 For example, incorporation of magnetic nanoparticles in the barrier of magnetic tunnel junctions hasbeen theoretically predicted to demonstrate a very high magnetoresistance 8 and higher order tunneling effects have also been experimentally observed in similar systems. 9, 10 In terms of applications, resistive switching is an interesting phenomenon also observed in magnetic granular films. 11,12 However, along with the changes in the resistance of the granular system in the presence of an electric field, the magnetic moment of the granules will also be affected and this has not been investigated either through experiments or theoretical modeling. Another effect of the high electric field can be the migration of the oxygen atoms from the oxide matrix into the Co granules which would affect the magnetization of the granules.In this work, we investigate the effect of electric field on the magnetization of Co granules in the sputter deposited Co/Al 2 O 3 based magnetic granular system. In the low field regime we show systematic and reproducible changes in the net magnetic moment of the system 3 using in-situ ...