Dissertation > Excellent graduate degree dissertation topics show

Studies on the Preparation and Magnetoelectric Coupling Properties of Co/Co3O4/PZT Composite Films

Author: ZhouHang
Tutor: WanJianGuo
School: Nanjing University
Course: Condensed Matter Physics
Keywords: exchange bias composite film magnetoelectric effect magneticcapacitor
CLC: O484.1
Type: Master's thesis
Year: 2012
Downloads: 13
Quote: 0
Read: Download Dissertation


Multiferroic material is a kind of material with the coexistence of ferroelectric and ferromagnetic orderings or other order parameter, and the coupling interaction between them engenders the materials with the unique magnetoelectric effect, it is widely used in the area of storage and sensory, the magnetoelectric voltage coefficient of the single-phase compounds is too small and most of them would show magnetoelectric effect only at low temperature, so it is difficult for the single-phase multiferroic compounds to be used. Comparatively, the magnetoelectric effect in the composite multiferroic materials is much higher than that of the single-phase compounds. So it is promising for the multiferroic composites to be used in the practical application.In the system of ferromagnetic/antiferromagnetic, exchange bias effect will appear when the temperature reduces below Neel temperature of the antiferromagnetic material. When the magnetic domain of ferromagnetic materials reversals with the external magnetic field, it need to overcome the pinning effect of the anti-ferromagnetic material, resulting the offset of the hysteresis loop to the opposite direction of the cooling field. In the system of CO/CO3O4, the Neel temperature is about40K, so we expect that the exchange bias effect would appear when the temperature drops below40K. Pb(Zro.52Ti0.48)03(PZT) is a kind of multiferroic material with piezoelectric effect, the purpose of this paper is to successfully make CO/CO3O4/PZT composite film, and expect to observe the magnetoelectric coupling effect. The main results are as following:Focusing on the fabrication and characterization of cobalt and cobalt oxide films, we successfully prepared cobalt and cobalt oxide film by cluster beam deposition, magnetron sputtering deposition system and pulsed laser deposition system. Then we made characterization on the film and find the cobalt clusters made by cluster beam deposition hade uniform size. The micrographs of TEM shows that the cobalt nanoclusters are5nm in size and are all cubic crystal. The film made by magnetron sputtering deposition system is very flat on the surface. We also measured the resistance of cobalt oxide at low temperature and found the resistance increased as the temperature decreased.We successfully prepared PZT film by Sol-Gel method and then made CO/CO3O4/PZT composite film, after that, we measured magnetic and electrical properties of composite film. SEM photography shows the surface of composite film is dense and smooth, the thickness of Co layer is approximately30nm, the thickness of CO3O4layer is about25nm and the thickness of PZT layer is about180nm. We know the Neel temperature of CoO is almost290K, higher than that temperature of CO3O4(40K). VSM measurements at different temperatures showed that exchange bias happened of composite film at about77K, proved the existence of CoO.We first used PPMS to measure the capacitance with varies temperature at different magnetic field, and found the capacitance mainly decreased as the temperature changed from300K to10K and there were mutations at180K and40K, we consider the mutation at180K was occurred by the phase transition of PZT from tetragonal to rhombohedral phase while the mutation at40K was caused by the transition from paramagnetic to antimagnetic. When magnetic field was applied on the composite film, the center position of the peak shifted to190K while there was no shift at40K. The shift at190K was mainly caused by the internal stress of the PZT film, indicating there is magnetoelectric coupling effect in composite film.Then we used PPMS to measure the capacitance with varies magnetic field at different temperature, found the capacitance curve would become asymmetry at low temperature due to the existence of exchange bias. When the magnetic field was positive, The magnetic capacitance of the film is about-7%and would not change with temperature. When the magnetic field was negative, The magnetic capacitance of the film is very small(no more than1%) and would became smaller as the temperature decreased. The significant inconsistency of the magnetic capacitor in the positive and negative magnetic field is mainly caused by the exchange bias effect at low temperature. When the magnetic field is positive, the antiferromagnetic layer has tiny affection to the switching of Co magnetic domain, therefor the efficiency of the magnetic-force-electric coupling is high and the magnetic capacitance increases significantly; when the magnetic field is negative, due to the strong pinning effect of the antiferromagnetic layer, the Co magnetic domain flipping needs to overcome the exchange coupling, resulting serious decline of magnetic-force-electric coupling in the composite film and the magnetic capacitance changes very little.

Related Dissertations

  1. The Preparation and the Properties of the Composite Films from Cassava Starch and Guar Gum,TS236.9
  2. Preparation and Properties of Poly(lactic Acid)/Acetylated Starch Composite Films,R318.08
  3. Research on Preparation of Dopamine Composite Films on Stainlees Steel and Corrosion Resistance,TG174.44
  4. Electrophoretic Deposition of Ferromagnetic Films and Magnetoelectric Composite Films,TB383.2
  5. Multicomponent gradient composition of rigid composite film cutter,TG71
  6. Multi-block type sulfonated poly ether sulfone proton exchange membrane preparation and properties of,TM911.4
  7. Photocatalysis Study of Cu2 O/TiO2 Composite Film Prepared by Direct Current Reactive Magnetron Sputtering,O643.36
  8. Exchange Bias in Charge Ordering Manganite Nanoparticles,TB383.1
  9. Study on the Process Technique of Whey Protein Based Films and Antimicrobia Properties of the Composite Films,TS201.21
  10. Study on the Influence of the Surface Anisotropy and Shape on the Magnetic Properties of Nanoparticles,TB383.1
  11. Preparation and Photoelectric Performance of Graphene/TiO2 Composite Films,TB383.2
  12. The Application of Attapulgite Clay Modified Electrode in the Electrochemical Sensors,TP212.2
  13. Investigation on Modified Nafion Proton Exchange Membrane for PEMFC,TM911.4
  14. Proton exchange membrane fuel cell synthesis and properties of,TM911.4
  15. Study on the Magnetism of Phase Separation and Magnetocaloric Effect of Rare-earth Manganites,O482.5
  16. Experimental Study on Thermoelectric for Aluminum Cell Wall Waste Heat,TM617
  17. Removal of 2, 4-dichlorophenol from Aqueous Solution by Chitosan/Activated Carbon Fiber/TiO2 Composite Membrane,X703
  18. Nano CaCO_3 / chitosan composite characteristics and preservation of function studies,TB383.1
  19. Study on the Preparation and Properties of Layer-By-Layer Self-Assembled LDHs/Polyelectrolyte Composite Films,TB383.2
  20. The Fabrication and Study on Hydrogen Peroxide Biosensor,TP212.3
  21. Research on Thermal Stability of Spin Valve Structured Multilayer Films,O482.54

CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics > Film growth,structure and epitaxy
© 2012 www.DissertationTopic.Net  Mobile