Abstract/Details

Magnetic properties and structure of pulsed laser deposited nickel ferrite films


2009 2009

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Abstract (summary)

Series of heteroepitaxy spinel ferrite thin films (NixFe 3-xO4) were prepared by the alternating target laser ablation deposition (ATLAD) technique. Different from conventional pulsed laser ablation deposition (PLD), the AT-LAD technique allows different laser pulses incident upon multiple targets alternatively to grow the film in an atomic layer-by-layer fashion. In this research, targets of NiO and Fe2O3 were used to grow Nix Fe3-xO4 films on single crystal MgO (111) substrates. The substrate temperature and oxygen pressure were fixed at 900°C and 5 mTorr, respectively. Values of x were varied by changing the number of laser pulses on NiO and Fe2O3 targets within each cycle.

NixFe3-xO 4 films, with spinel structure oriented along <111> direction, were characterized by CuKα x-ray diffraction (XRD). The maximum lattice parameter (8.353 Å) was obtained at a laser shot ratio Fe:Ni∼2 which is also larger than the bulk value (8.339 Å) [2]. We studied the surface and cross-section morphology using scanning electron microscope (SEM). The SEM images revealed triangle shaped grains oriented along the substrate orientation, the <111> direction. Energy dispersive x-ray analysis (EDAX) was utilized to identify the atomic ratios of Ni and Fe elements. It is revealed Fe:Ni is close to 2 when the laser pulses on NiO and Fe2O3 target were 5 and10 per ATLAD cycle, respectively. The saturation magnetization, was 4πMs, of the NiFe 2O4 thin films, measured by vibrating sample magnetometer (VSM), ∼4,000G, which is larger than the bulk value (∼3,400G)[12].

Microwave properties were measured using a ferromagnetic resonance (FMR) spectrometer. Using the Smit & Beljar FMR equations[9], the minimum anisotropy constants, K = -238700 (erg/cm 3), obtained corresponding to an atomic ratio Fe:Ni∼2. The maximal FMR linewidth, ΔH(Oe)=1061(Oe), was also obtained from this film. The corresponding effective gyromagnetic factor (g eff) is 2.00, which is obtained using the plot of f as a function of Hi.

We calculated the cation distribution based on EDAX determined atomic ratio (Fe:Ni) and the measured 4πMS. This information can also be confirmed by synchrotron based x-ray absorption spectra analysis. The results indicated more Ni ions on A sites in ATLAD films compared with bulk. This explains the expanded lattice parameter and the increase of 4π MS.

Indexing (details)


Subject
Electrical engineering
Classification
0544: Electrical engineering
Identifier / keyword
Applied sciences; Magnetic properties; Nickel ferrite films; Pulsed laser deposition; Structure
Title
Magnetic properties and structure of pulsed laser deposited nickel ferrite films
Author
Chang, Huiching
Number of pages
104
Publication year
2009
Degree date
2009
School code
0160
Source
MAI 47/03M, Masters Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780549949671
Advisor
Harris, Vincent G.
Committee member
Carmine, Vittoria; Ziemer, Katherine S.
University/institution
Northeastern University
Department
Electrical and Computer Engineering
University location
United States -- Massachusetts
Degree
M.S.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
1460816
ProQuest document ID
231396458
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/231396458
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