sankar anandakumar - Academia.edu (original) (raw)

Papers by sankar anandakumar

Sensors and Actuators A: Physical, 2012

Please cite this article in press as: B. Sinha, et al., Micro-magnetometry for susceptibility mea... more Please cite this article in press as: B. Sinha, et al., Micro-magnetometry for susceptibility measurement of superparamagnetic single bead, Sens. Actuators A: Phys. (2012), http://dx.

Thin Solid Films, 2010

We present the observation of double shifted hysteresis loops in IrMn/NiFe bilayer structures. Th... more We present the observation of double shifted hysteresis loops in IrMn/NiFe bilayer structures. The bilayer structures were fabricated using high vacuum DC magnetron sputtering system. The hysteresis loops of the as deposited samples show the double shifted loops at NiFe layer thicknesses 5 nm and 6 nm, whereas the IrMn layer thickness was kept constant at 15 nm. The results were interpreted as the contribution of both positive and negative exchange bias fields. We suppose that this phenomenon is occurring due to the ferromagnetic (FM) layer exchange coupled with the antiferromagnetic (AFM) layer in two different magnetization directions. The ferromagnetic coupling of the interface spins in some regions of the film generates the hysteresis loop shift toward negative fields and antiferromagnetic coupling toward positive fields in the other regions. The double shifted hysteresis loops disappeared after magnetic field annealing of the samples above Neel temperature of the AFM layer. The X-ray diffraction patterns of the sample show the IrMn (111) crystalline growth necessary for the development of exchange bias field in this system. The correlation between the Magnetic Force Microscopy (MFM) domain structures of the as deposited sample and the magnetization reversal process of the double shifted hysteresis loops were discussed. The results suggest that the larger multidomain formation in the AFM layer with different magnetization directions was responsible for the positive and negative exchange bias fields in IrMn/NiFe bilayer samples.

Japanese Journal of Applied Physics, 2011

In this study, we have investigated real-time decoding feasibility of magnetic micro-barcodes in ... more In this study, we have investigated real-time decoding feasibility of magnetic micro-barcodes in a microfluidic channel by using numerical analysis of magnetic field distribution of the micro-barcodes. The vector potential model based on a molecular current has been used to obtain magnetic stray field distribution of ferromagnetic bars which consisting of the micro-barcodes. It reveals that the stray field distribution of the micro-barcodes strongly depends on the geometries of the ferromagnetic bar. Interestingly enough, we have found that one can avoide the miniaturization process of a magnetic sensor device needed to increase the sensitivity by optimizing the geometries of micro-barcodes. We also estimate a magnetic sensor response depending on flying height and lateral misalignment of the micro-barcodes over the sensor position and found that control of the flying height is crucial factor to enhance the detection sensitivity and reproducibility of a magnetic sensor signal in the suspension assay technology. #

IEEE Transactions on Magnetics, 2000

An array of CoNiP magnetic nanowires were grown in polycarbonate membrane using potentiostatic el... more An array of CoNiP magnetic nanowires were grown in polycarbonate membrane using potentiostatic electrodeposition technique under three electrodes configuration. The commercially available track etched polycarbonate membranes of thickness 6 m with pore size of 50 nm diameter were used in these experiments. The electrolyte bath consists of NiCl 2 -6.81 g/l, CoCl 2 -2.76 g/l, NaH 2 PO 2 -2.59 g/l, H 3 BO 3 -2.49 g/l, NaCl-2.20 g/l, Saccharin-0.8 g/l was used for deposition of CoNiP magnetic nanowires. The main aim of this work focuses on growth conditions, structural and magnetic properties of the CoNiP nanowires. In this context first we observed three different growths of nanowire lengths 1.21 m, 4.31 m and 6 m at three different deposition times 30 min, 60 min, and 90 min, respectively. The X-ray diffraction patterns of CoNiP nanowires have shown the intermixture of fcc and hcp phases. The structural properties of the CoNiP nanowires were observed using scanning electron microscope (SEM). The magnetic properties of the CoNiP nanowires were observed using vibrating sample magnetometer (VSM), which show hard magnetic properties with no preferential magnetization direction of the nanowires having high coercivity values around 500 Oe.

Sensors and Actuators A: Physical, 2012

Please cite this article in press as: B. Sinha, et al., Micro-magnetometry for susceptibility mea... more Please cite this article in press as: B. Sinha, et al., Micro-magnetometry for susceptibility measurement of superparamagnetic single bead, Sens. Actuators A: Phys. (2012), http://dx.

Thin Solid Films, 2010

We present the observation of double shifted hysteresis loops in IrMn/NiFe bilayer structures. Th... more We present the observation of double shifted hysteresis loops in IrMn/NiFe bilayer structures. The bilayer structures were fabricated using high vacuum DC magnetron sputtering system. The hysteresis loops of the as deposited samples show the double shifted loops at NiFe layer thicknesses 5 nm and 6 nm, whereas the IrMn layer thickness was kept constant at 15 nm. The results were interpreted as the contribution of both positive and negative exchange bias fields. We suppose that this phenomenon is occurring due to the ferromagnetic (FM) layer exchange coupled with the antiferromagnetic (AFM) layer in two different magnetization directions. The ferromagnetic coupling of the interface spins in some regions of the film generates the hysteresis loop shift toward negative fields and antiferromagnetic coupling toward positive fields in the other regions. The double shifted hysteresis loops disappeared after magnetic field annealing of the samples above Neel temperature of the AFM layer. The X-ray diffraction patterns of the sample show the IrMn (111) crystalline growth necessary for the development of exchange bias field in this system. The correlation between the Magnetic Force Microscopy (MFM) domain structures of the as deposited sample and the magnetization reversal process of the double shifted hysteresis loops were discussed. The results suggest that the larger multidomain formation in the AFM layer with different magnetization directions was responsible for the positive and negative exchange bias fields in IrMn/NiFe bilayer samples.

Japanese Journal of Applied Physics, 2011

In this study, we have investigated real-time decoding feasibility of magnetic micro-barcodes in ... more In this study, we have investigated real-time decoding feasibility of magnetic micro-barcodes in a microfluidic channel by using numerical analysis of magnetic field distribution of the micro-barcodes. The vector potential model based on a molecular current has been used to obtain magnetic stray field distribution of ferromagnetic bars which consisting of the micro-barcodes. It reveals that the stray field distribution of the micro-barcodes strongly depends on the geometries of the ferromagnetic bar. Interestingly enough, we have found that one can avoide the miniaturization process of a magnetic sensor device needed to increase the sensitivity by optimizing the geometries of micro-barcodes. We also estimate a magnetic sensor response depending on flying height and lateral misalignment of the micro-barcodes over the sensor position and found that control of the flying height is crucial factor to enhance the detection sensitivity and reproducibility of a magnetic sensor signal in the suspension assay technology. #

IEEE Transactions on Magnetics, 2000

An array of CoNiP magnetic nanowires were grown in polycarbonate membrane using potentiostatic el... more An array of CoNiP magnetic nanowires were grown in polycarbonate membrane using potentiostatic electrodeposition technique under three electrodes configuration. The commercially available track etched polycarbonate membranes of thickness 6 m with pore size of 50 nm diameter were used in these experiments. The electrolyte bath consists of NiCl 2 -6.81 g/l, CoCl 2 -2.76 g/l, NaH 2 PO 2 -2.59 g/l, H 3 BO 3 -2.49 g/l, NaCl-2.20 g/l, Saccharin-0.8 g/l was used for deposition of CoNiP magnetic nanowires. The main aim of this work focuses on growth conditions, structural and magnetic properties of the CoNiP nanowires. In this context first we observed three different growths of nanowire lengths 1.21 m, 4.31 m and 6 m at three different deposition times 30 min, 60 min, and 90 min, respectively. The X-ray diffraction patterns of CoNiP nanowires have shown the intermixture of fcc and hcp phases. The structural properties of the CoNiP nanowires were observed using scanning electron microscope (SEM). The magnetic properties of the CoNiP nanowires were observed using vibrating sample magnetometer (VSM), which show hard magnetic properties with no preferential magnetization direction of the nanowires having high coercivity values around 500 Oe.