Papers by Keyword: MFM

Abstract: In the present study we prepared NiFe₂O₄, Ni_0.95Cu_0.05Fe₂O₄ and Ni_0.94Cu_0.05Co_0.01 Fe₂O₄ thin films by metallo-organic decomposition method (MOD) using spin coating technique. The samples were characterized by XRD. XRD patterns of thin films confirmed the formation of cubic spinel structure without any secondary phase. For microstructural analysis we characterized samples by Scanning Probe Microscope (SPM). From Atomic force microscopy (AFM), we analyzed surface morphology, calculated grain size, roughness and porosity. It has been found that grain size and roughness affected by Cu, Co substitution. After this we carried out magnetic force microscopy (MFM) on the samples. Effect of substitution on magnetic grains was observed from MFM.

Abstract: This study presents the results of an analysis of the domain structure of supersaturated X2CoCrMoAl20-15-3 maraging steel. The analyses was carried out using the magnetic force microscopy method in a two pass mode. Obtained magnetic results were subjected to numerical analysis. The dimensions of spontaneously magnetized regions and their orientation were determined by analyzing the autocorrelation function of changes in the resonant frequency of the MFM probe. The use of fractal analysis was proposed to describe the domain structure.

Abstract: Evolution of domain structures across the martensitic transition (Tm) in the ferromagnetic shape memory alloy system Ni-Mn-Ga is studied using an optical microscope with a temperature variation. Compositions chosen have Tm < Tc, Tm = Tc and Tm > Tc, (Tc=Curie temperature) so that one can compare the nature of martensitic domains. There are no appreciable domain structures when Tm < Tc as compared to the one with Tm > Tc. However, giant morphological changes in the form of appearance of well-developed domains that are propagating with different directions are seen for the composition in which Tm=Tc. The results are discussed in the light of Magnetic Force Microscopy observations as well as giant entropy changes known to occur on samples with co-occurrence of Tm and Tc.

Abstract: The magnetic properties of an ultrathin cobalt film were modified by a focused femtosecond pulsed laser beam. The Co wedge, with a thickness ranging from 0 to 2 nm, sandwiched by Au films was prepared using ultra-high vacuum magnetron sputtering on a mica substrate. The modifications of the laser induced magnetic anisotropy were investigated using magneto-optic Kerr microscopy and MFM/AFM techniques. The laser induces: (i) local reorientation of magnetization from an in-plane to a perpendicular state and (ii) an increase of the coercivity field. A corresponding increase of the perpendicular magnetic anisotropy is discussed considering an improvement of the Co/Au interfaces.

Abstract: In this study, the dipole switching and non-volatile memory functionality of poly(vinylidene fluoride-trifluoroethylene) (PVDF/TrFE)(72/28 mol%) random copolymer ultrathin films were analyzed. PVDF/TrFE(72/28) used as ferroelectric insulator in varying memory device architectures such as metal-ferroelectric polymer-metal (MFM), MF-insulator-semiconductor (MFIS), MIS and ferroelectric field-effect transistors (FeFET) were examined using different electrical measurements. A maximum data writing speed of 1.69 MHz was calculated from the switching time measured using MFM architecture. Compared to MFM, MFIS device architecture was found to be more suitable for distinguishing the ‘0’ and ‘1’ state using the capacitance-voltage measurement. With FeFET, the measured drain current (Id) as well as its memory window increased with decreasing channel length, thereby enabling the easier identification of ‘0’ and ‘1’ state comparable to the MFIS case. The data obtained from this study will be useful in the fabrication of non-volatile random access memory (NVRAM) devices operating at lower voltage with faster data R/W/E speed and memory retention capability.

Abstract: BiFeO3 films were prepared by chemical solution method on Pt/Ti/SiO2/Si substrates. The ferroelectric properties of Pt/BiFeO3/Pt capacitors were investigated, and the effect of recovery annealing applied after Pt top electrode deposition was discussed. The pure phase film with recovery annealing exhibits lower leakage current and higher remanent polarization than those without post-annealing. The leakage current is reduced by three orders of magnitude, the remanent polarization increases from 2.59μC/cm2 to 3.44μC/cm2. The recovery anneals applied after top electrode deposition may optimize the ferroelectric performance by removing the effect of structural defects formed by sputtering.

Abstract: The new hybrid device consisting of patterned array of Co nanodots on GaMnAs channel was fabricated and demonstrated to give a new functionality to control the transport properties of GaMnAs. Magnetic state of array of Co nanodots was observed with magnetic force microscopy (MFM) observation. The magnetic state of individual Co dots can be controlled by using a MFM tip. Different distribution of magnetic state of Co nanodots in an array structure resulted in an inhomogeneous magnetic field. Magnetic field induced by the array of nanodots leads to change in the transport properties of GaMnAs. This inhomogeneous magnetic field was regarded to act as an effective potential that can trap the spin polarized carriers in the GaMnAs system with giant Zeeman splitting.