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Title: Growth of Nano-Structured Thin Films of Magnetic Materials by PLD Technique
Authors: Anjum, Safia
Keywords: Natural Sciences
Issue Date: 2010
Abstract: This project is aimed to deposit magnetic thin films by Pulsed Laser Deposition (PLD) technique. A KrF Excimer laser (248 nm, 20 ns) operated at 20 Hz was used as an energy source for the deposition. Films are deposited under various deposition conditions, like substrate temperature, oxygen pressure, post annealing and applied external magnetic field depending upon the target material characteristics. On the basis of the structure the deposited films are classified as cubic spinel ferrites (NiFe 2 O 4 and ZnMnZrFeO), Hexaferrite (BaFe 12 O 19 ) and Alloy (NdFeCo). NiFe 2 O 4 thin films (cubic spinel ferrites) show that the monotonic increase in saturation magnetization and non-monotonic increase in electrical conductivity depends on the oxygen partial pressure during the growth of the thin films. Another spinel cubic ferrite Zn 0.2 Mn 0.81 Zr 0.01 Fe 1.98 O 4 and Zn 0.2 Mn 0.83 Zr 0.03 Fe 1.94 O 4 thin films with different concentration of Mn and Zr were deposited on single crystal n-Si (400) at room temperature (RT). The films are also deposited under external magnetic filed.The results reveal the effect of external applied magnetic field on the growth of films in terms of small particle size, improved uniformity, lower r.m.s. roughness, higher magnetization and increased thickness. The reflection of Zn 0.2 Mn 0.83 Zr 0.03 Fe 1.94 O 4 thin films are higher than Zn 0.2 Mn 0.81 Zr 0.01 Fe 1.98 O 4 thin films due to the greater concentration of Zr. The band gap energy E g decreases with increase in film thickness. In the case of Hexaferrites, the low substrate temperatures (room temperature to 200 o C) restrict the formation of larger grains. Whereas, for the higher substrate temperature i.e, 400 o C, the grain size of the deposited thin film are much larger. The substrate temperature caused the uniaxial magnetic anisotropy. The higher values of coercivity, squareness and films thickness are associated with the growth of larger grains at higher substrate temperature. For the films deposited under applied magnetic field, the saturation magnetization increases monotonically as the applied field value increases during deposition. Band gap energy (Eg) increases with increasing thickness. With the application of external magnetic field, the magnetic and optical properties of the thin films are significantly enhanced. Rare earth transition metal doped (NdFeCo) thin films (Alloy) were fabricated on Si substrate keeping the substrate temperature constant at 300 o C. Thin films were deposited without and under the influence of various transverse applied magnetic field. All the films exhibit perpendicular magnetic anisotropy. The thickness of the film increases monotonically whereas the saturation magnetization and optical band gap eneggy increases non- monotonically. The maximum value of Ms and Eg are found when the applied magnetic field value is 4.5 KOe. Magnetic, optical and structural properties of the ferrite thin films (cubic, hexa-ferrites and alloy) are strongly influenced by the deposition conditions. The optimization of the deposition conditions can play an important role to replace the thin films with the bulk material.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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