Fabrication,Characterizations And Magnetic Response Of Five Different Nanoarchitectures And Fe-CoNi Core-Shell Nanostructure

Cobalt-Nickel(CoNi)alloy nanotubes(NTs)with diameters 50(D1),100(D2),150(D3),and 200 nm(D4)have been fabricated using Anodic Aluminum Oxide(AAO)membranes.X-ray diffraction spectroscopy(XRD),field-emission scanning electron microscopy(FE-SEM),vibrating-sample magnetometer(VSM),and physical property measurement system(PPMS)analysis method were employed to systematically investigate the structural,morphological and magnetic properties of CoNi NTs samples.Magnetization reversal mechanism has been explained by angular dependence of coercivity.Low temperature studies have shown that coercivity H_C of nanotubes follows the thermal activation model.The temperature dependence of H_C follows the3/2 power law for the field dependence of energy barriers.Core-shell nanoarchitectures are novel classes of nonstructural materials for their capacious applications.Iron(Fe)electrodeposited inside Cobalt-Nickle(CoNi)alloy nanotubes(NTs)were synthesized using two-step dc potentiostatic electrodeposition method within the nanopores of anodized aluminum oxide(AAO)template.The X-ray diffraction and electron microscopy confirm the presence of base cubic center(bcc)phase structure for Fe and face cubic center(fcc)for CoNi at core and shell region respectively.A comparative study of magnetization reversal mechanism has been done by verifying the angular dependence of coercivity(H_C)which is further in terms of thermal activation over an energy barrier with a 3/2 power dependence on the field.Furthermore,the parallel magnetization per unit area(M_S/A)is found to be strongly dependent on the diameter of AAO templates,which shows a linear response as the diameter increases.Heusler type one-dimensional nanogeometries Ni₂Fe Ga have been fabricated in the nanopores of 150 nm AAO(Anodic Aluminum Oxide)templates using simple and low-cost electrodeposition technique at room temperature.The structure of prepared nanoarchitectures is L2₁ Phase with a secondary?phase.Magnetic properties have been studied at room temperature as well as at low temperatures.It has been found that saturation magnetization M_S decreases as temperature rises.The nanowires have maintained ferromagnetic behavior from 5 K to 350 K.The Ni₂Fe Ga nanowires(NWs)and nanotubes(NTs)have the same saturation magnetization.The difference of the resonance field Hr is mainly attributed to the difference of the anisotropy field H_k under the fixed microwave frequency.Hr for the NT sample is smaller than that for the NW sample.Permalloy nanotubes(NTs)were fabricated in the nanopores of 100 nm AAO(Anodic Aluminum Oxide)template by using a low-cost electrodeposition process at room temperature.As prepared Ni₈₀Fe₂₀ NTs morphology,elemental analysis,structural analysis was investigated by using field-emission scanning electron microscopy(FE-SEM),energy dispersive X-ray(EDX)and X-Ray diffraction respectively.The structure of prepared Permalloy nanoarchitectures is face cubic centered(fcc)phase with polycrystalline.After the initial formations,the Ni₈₀Fe₂₀NTs was annealed at 200,400,and 600°C.The vibrating sample measurement(VSM)showed that all the samples were ferromagnetic.Furthermore,VSM has been employed to study the magnetic properties including saturation magnetization(M_S),squareness(SQ),and coercivity as a function of annealing temperature.A comparative study of the magnetization reversal mechanism has been done by verifying the angular dependence of coercivity(H_C).Shape anisotropy played the dominant role to orient the magnetic moments along the NTs long axes.Annealing temperature improved the magnetic properties of Permalloy NTs.Multiferroic nanogeometries as like BaTiO₃(BTO)and Bi₂Fe Cr O₆(BFCO)were synthesized in AAO(Anodic Aluminum Oxide)templates with an average diameter of100 nm using sol-gel route.BTO was annealed at 700°C whereas BFCO at 630°C.The structural,composition analysis and phase of both multiferroic were investigated by using FE-SEM,EDX,and XRD respectively.The phase of BTO is a cubical perovskite structure whereas BFCO with hexagonal double perovskite structures.