Structural Characterization of PLD-grown Nanometer Size Ferromagnetic NiFeMo films
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1200-G09-05
Structural Characterization of PLD-grown Nanometer Size Ferromagnetic NiFeMo films Mitali Banerjee1, A. K. Majumdar1, R. J. Choudhary2, D. M. Phase2, S Rai3, Pragya Tiwari3, G. S. Lodha3 1
Materials Science, S N Bose National Centre for Basic Sciences, Kolkata 700098, India.
2
UGC-DAE Consortium for Scientific Research, Indore 452017, India.
3
Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
ABSTRACT Thin films of 3 different thicknesses each of Ni83.2Fe3.3Mo13.5 and Ni83.1Fe6.0Mo10.9 alloys have been grown using Pulsed Laser Deposition (PLD) technique. Our motivation is to investigate the magnetic properties of a few nm thick Ni alloys with mostly Mo (4d element) addition since the corresponding soft ferromagnetic bulk alloys have shown very small coercivity of ~ 0.1 Oe. Detailed structural characterization has been undertaken before probing the magnetic properties. Arc melted alloy buttons after homogenization are used directly as targets for the deposition. Films were deposited on single crystal Sapphire (0001) substrates using excimer laser. The structural characterization has been done by X-ray Diffraction (XRD), X-ray Reflectivity (XRR), Energy Dispersive X-ray Spectroscopy (EDS), and Atomic Force Microscopy (AFM). The X-ray diffraction pattern shows that the films are highly textured and grown along [111] direction of the alloys. They have high lattice strain which makes the films highly resistive and the resistance decreases with increasing thickness. The EDS measurements, using Scanning Electron Microscope (SEM), indicate that the compositions of the films are almost the same as those of the targets. Thickness, roughness, and density gradients are estimated using XRR measurements. The thinner films have higher roughness compared to the thicker ones for both the compositions. The films have density gradient across their thickness. The bottommost low density layer has high roughness which is supposed to be the result of initial non uniform coverage of the substrate. The density of the middle layer, having the lowest roughness, is approximately near the bulk value and it increases with increasing film thickness. The change in density is not due to the variation of composition; instead it is due to the variation of void densities in the layers. The topmost layer, having the lowest density and the highest roughness, is interpreted as a porous layer which is also evident from the AFM images.
INTRODUCTION Soft ferromagnetic materials have received a lot of attention due to their potential applications as transformer cores. Recently soft ferromagnetic thin films are widely used
in sensor technology, specially the binary Ni80Fe20 because alloys close to this composition have high initial permeability. A small amount of other transition metals, particularly molybdenum, could make the permeability1 even higher. A large number of work on magnetic properties of electrodeposited NiFeMo alloy films have been reported as these soft magnetic films are the critical components of hard d
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