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Unlocking the potential of half-metallic Sr2FeMoO6 thin films through controlled stoichiometry and double perovskite ordering

Hauser, Adam J.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1291048729

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Physics.
Sr2FeMoO6 is the most studied half-metallic double perovskite with the potential for room-temperature magnetoelectronic applications due to its Curie temperature above 400 K. Despite its promise, researchers have not yet succeeded in growing films of sufficient quality to realize its potential. By identifying and controlling critical factors that complicate attempts to grow thin films of Sr2FeMoO6, we have overcome the obstacles of non-stoichiometry, impurity phase formation and poor double perovskite ordering, all of which must be overcome to achieve half-metallicity. This dissertation reports an in-depth investigation that addresses several critical issues about the deposition of Sr2FeMoO6 epitaxial films using off-axis ultrahigh vacuum sputtering. High quality Sr2FeMoO6 films have been grown by off-axis ultrahigh vacuum DC magnetron sputtering, and characterized by a wide variety of techniques. We have discovered that sputtering gas pressure plays a dominant role in the stoichiometry and phase formation of Sr2FeMoO6 films. Film stoichiometry was found via Rutherford backscattering spectroscopy (RBS) and electron dispersive x-ray (EDX) spectroscopy to be both position dependent and pressure dependent in off-axis magnetron sputtering, changing from a Mo:Fe ratio of 1.43:1 at PTot = 70 mTorr to 1.12:1 at PTot = 6.7 mTorr. Our Sr2FeMoO6 films exhibit a combination of desired properties expected for its half-metallicity. X-ray-diffractometry (XRD) shows the films to be epitaxial, pure-phase, and well ordered by Reitveld refinement (ξ = 85.4%). High angle annular dark field scanning transmission microscopy (HAADF STEM) was performed to give the first direct observation of double perovskite ordering in a film, as well as a low defect level. Magnetic characterization was done via vibrating sample magnetometry (VSM) and superconducting quantum interference device (SQUID) magnetometry to find a saturation magnetization of 2.6 µB per formula unit at T = 5 K and a Curie temperature TC of 380 K, roughly in line with expectation for the film stoichiometry and ordering level. This dissertation also reports the first known report of distinct magnetic shape anisotropy, suggesting a high quality film with long-range magnetic ordering. The Sr2FeMoO6 films with these attributes will provide the material base for magnetoelectronic applications that will eventually achieve its half-metallic potential.
Fengyuan Yang (Advisor)
Leonard Brillson, J (Committee Member)
Klaus Honscheid (Committee Member)
Nandini Trivedi (Committee Member)
166 p.
Physics
Sr2FeMoO6; double perovskite; half metallicity; complex oxides

Recommended Citations

Citations

  • Hauser, A. J. (2010). Unlocking the potential of half-metallic Sr2FeMoO6 thin films through controlled stoichiometry and double perovskite ordering [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291048729

    APA Style (7th edition)

  • Hauser, Adam. Unlocking the potential of half-metallic Sr2FeMoO6 thin films through controlled stoichiometry and double perovskite ordering. 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1291048729.

    MLA Style (8th edition)

  • Hauser, Adam. "Unlocking the potential of half-metallic Sr2FeMoO6 thin films through controlled stoichiometry and double perovskite ordering." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291048729

    Chicago Manual of Style (17th edition)

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