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Pulsed laser deposition of Spinel Ferrites

Selected Projects Summary

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Correlation between cation distribution and enhanced magnetic properties in copper ferrite thin films


Copper ferrite films have been deposited on (100) MgO substrates by pulsed laser deposition. In a pursuit of the best growing condition, oxygen pressure used in deposition was varied from 1 mTorr to 120 mTorr with the substrate temperature varied from 600oC to 900oC. Magnetization values are measured to increase with oxygen pressure reaching a maximum value of 2480 G1, a 42% increase over the bulk equilibrium value as seen in Figure 1. Extended x-ray absorption spectroscopy (Fig. 2) shows that the Cu cation inversion, δ, (defined as (Cu1-δFeδ)tet[CuδFe2-δ]octO4) decreases monotonically from 0.72 to 0.55 with increasing saturation magnetization shown in Figure 3. The sample processed at 90 mTorr had the lowest inversion parameter at 0.55 compared with the bulk value of 0.85 and the highest magnetization.

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FIG.1. Variation of saturation magnetization of copper ferrite thin films as a function of oxygen pressure used in pulsed laser deposition.

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FIG.2. Real part of the Fourier transform amplitude of EXAFS data with best fits (see text for details). Panels (a), (b), and (c) are for
Fe K edge absorption while panels (d), (e), and (f) are for the Cu K edge absorption. Deposition pressures are denoted on each panel.

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FIG.3. Variation of saturation magnetization as a function of inversion coefficient, δ.

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1. Aria Yang, Xu Zuo, Lei Chen, Zhaohui Chen, Carmine Vittoria, Vincent G. Harris, J. Appl. Phys. 97, 10G107 (2005)
2. Aria Yang, Zhaohui Chen, Xu Zuo, Dario Arena, Johnny Kirkland, Carmine Vittoria, and Vincent G. Harris, Appl. Phys. Letter, 86, 252510 (2005)

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Magnetic and microwave properties of alternating target laser ablation deposition (AT-LAD) of 'artificial' manganese ferrite thin films


Manganese ferrite is a partial inverse spinel which, when prepared by conventional growth techniques, has ~20% of the Mn2+ ions on the octahedral sublattice. Here we developed a new layer–by–layer growth scheme at atomic scale by which the percentage of Mn2+ ions on the octahedral sublattice can be artificially controlled1. Manganese ferrite films grown by this technique exhibits higher degrees of cation inversion when grown on {100} and {111} MgO substrates2. It was observed that saturation magnetization varied in a wide range of values depending on chemical composition and processing oxygen pressure3. Although bulk manganese ferrite was low anisotropy magnetic material, large uniaxial anisotropy even as high as 5KOe was observed at room temperature in the films deposited on {100} MgO substrates shown in figure 2. Further, the magnetically preferred direction of anisotropy field can be aligned either along the film plane or perpendicular to it . The ability to induce large magnetic anisotropy allows for new applications beyond X-band frequencies to be considered.

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Figure 1. Schematic of the Mn-ferrite (spinel) unit cell structure illustrating {100} alternating planes of octahedral and
tetrahedral cations. Planes containing only octahedrally coordinated cations are shaded for clarity (see text for details).

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Figure 2. Saturation magnetization (Ms) and magnetic anisotropy field (Hu) of Mn-ferrite films as a function of oxygen processing pressure.

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1. Xu Zuo, Fan Yang, R. Mafhoum, R. Karim, A. Tebano, G. Balestrino, V.G. Harris, and C. Vittoria, IEEE Trans. on Magnetics, 40, 2811 (2004)
2. Aria Yang, Vincent G. Harris, Scott Calvin, Xu Zuo, and Carmine Vittoria, IEEE Trans. on Magnetics, 40, 2802 (2004)
3. Xu Zuo, Aria Yang, Soack-Dae Yoon, Joe A. Christodoulides, Vincent G. Harris, and Carmine Vittoria, J. Appl. Phys. 97, 10G103 (2005)
4. Xu Zuo, Aria Yang, Soack-Dae Yoon, Joseph A. Christodoulides, Vincent G. Harris, and Carmine Vittoria,Appl. Phys. Lett., 87, 152505 (2005)

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Maintained by Aria Yang, Last updated on Nov. 3, 2008