Correlation of structural ordering with magnetic properties of pulsed laser deposited Co2FeGa Heusler alloy thin films

In the present contribution, structural and magnetic properties of Pulsed laser deposited (PLD) Co2FeGa (CFG) thin films have been studied as a function of substrate temperature. Structural investigation carried out by X-Ray Diffraction (XRD) measurement reveals mixed phase cubic structure of the films which changes from a nearly ordered to highly disordered phase with an increase in substrate temperature. Grazing Incidence X-Ray Diffraction (GIXRD) study shows the presence of disordered A2 phase similar to the bulk target. Grazing Incidence X-Ray Reflectivity (GIXR) measurement reveals the formation of bi-layer structure in the films with different density and thickness though the overall thickness remains same. Field Emission Scanning Electron Microscopy (FESEM) study shows the formation of a droplet-like morphology of the films. Extended X-ray Absorption Fine Structure (EXAFS) study serves a major role in complementing the XRD results and also shows a strong hybridization of Co with Ga maintaining the half metallicity. A novel approach in analyzing the EXAFS data additionally gives quantitative estimation of the different kinds of disorders present in the samples at the atomic level. In addition to this, magnetization result suggests that the films grown at lower substrate temperatures acts as proper ferromagnet following the well known spin wave theory with higher value of spontaneous magnetization in comparison to other samples. A lesser value of saturation magnetization in the films compared to bulk also supports the presence of antisite disorders

Role of oxygen impurity in growth and magnetic properties of Ni83Fe17 permalloy thin films

To study the influence of oxygen impurities in the sputtering atmosphere on micro structure,and the magnetic and magnetotransport properties,thin films of Ni83Fe17 were deposited under dc magnetron puttering technique into which regulated oxygen gas was introduced. The partial pressure of oxygen was varied from 2�10 7 to 3�10�6mbar.X- ray diffraction patterns indicate the reduction of grain growth ith increasing the oxygen partial pressure. The grain micro structure and the composition were confirmed through high resolution transmission electron microscopy attached with Scanning Transmission Electron Microscopy (STEM). Transition from canted to rectangular magnetic hysteresis loop was observed through magnetization measurements for samples prepared under higher oxygen partial pressure which implies the structural changes in the magnetic domain formation. These observations were further confirmed through the measurements of an isotropic magneto resistance properties

Influence of Au addition on magnetic properties of iron oxide in a silica–phosphate glass matrix

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Evolution of magnetoresistance behaviour at low temperatures in naturally oxidised specular spin valve systems

The temperature dependent magnetoresistive behaviour of field cooled naturally oxidised specular spin valve systems has been studied in the temperature range of 300–10 K. Inconsistent to the non-specular spin valve system, an anomalous behaviour was evolved with large exchange bias and higher coercivity, below 200 K. The structural investigations inferred the formation of magnetic oxides with higher density gradient in the pinned layer, and the observed anomalous behaviour at low temperatures was correlated with the antiferromagnetic ordering of these oxides in spin glass state. The uncompensated interfacial magnetism of the nano-oxide layer was further confirmed by comparing with low temperature magnetoresistive behaviour of non-magnetic oxide based specular spin valve systems

MgO based specular spin valve with reversible minor loop and higher exchange bias for futuristic linear magnetic field sensor

Specular spin valves (SVs) containing ultrathin MgO, structured as substrate/seed/AF/PL1/MgO/PL2/Cu/FL/MgO/cap, have been fabricated. Both structural and magnetic characterizations of MgO based specular spin valve (SSV) have been performed and compared them with the measured data on naturally oxidized (NO) and conventional spin valves (CSV), grown under optimised condition. Reversible minor loop characteristics, highest exchange bias of 625 G and 10% magnetoresistive (MR) ratio were important observations in MgO based system. Zero hysteresis behavior was confirmed due to the reduction of grain growth of the stacks above the fine-textured MgO layer, through X-ray diffraction measurements. Interestingly, at 10 K, above 100% enhancement in MR ratio was observed in MgO based system with marginal increase in coercivity of the order 1 G. On the other hand, NO based structure has 10% MR, minor loop hysteresis of 2 G and exchange bias of 560 G at room temperature; however at 10 K, only 75% enhancement in MR ratio with large anomalies in magnetic measurements attributes due to the AFM nature of oxide materials. The above studies reflects the superior performance of MgO based SSV over a wide range of temperature in comparison to other SV structures and may lead to futuristic linear magnetic field sensor applications