Browsing by Author "Cross, L. E."

Now showing 1 - 4 of 4
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    Destruction of spin cycloid in (111)(c)-oriented BiFeO3 thin films by epitiaxial constraint: Enhanced polarization and release of latent magnetization
    Bai, Feiming; Wang, Junling; Wuttig, Manfred; Li, Jiefang; Wang, Naigang; Pyatakov, Alexander P.; Zvezdin, Anatoly Konstantinovich; Cross, L. E.; Viehland, Dwight D. (AIP Publishing, 2005-01-01)
    In BiFeO3 films, it has been found that epitaxial constraint results in the destruction of a space modulated spin structure. For (111)c films, relative to corresponding bulk crystals, it is shown (i) that the induced magnetization is enhanced at low applied fields; (ii) that the polarization is dramatically enhanced; whereas, (iii) the lattice structure for (111)(c) films and crystals is nearly identical. Our results evidence that eptiaxial constraint induces a transition between cycloidal and homogeneous anti ferromagnetic spin states, releasing a latent antiferromagnetic component locked within the cycloid. (C) 2005 American Institute of Physics.
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    Epitaxially induced high temperature (> 900 K) cubic-tetragonal structural phase transition in BaTiO3 thin films
    Bai, Feiming; Zheng, H. M.; Cao, Hu; Cross, L. E.; Ramesh, R.; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2004-11-01)
    For (001)(c) oriented BaTiO3 thin films, it has been found that epitaxial constraint can result in a dramatic increase in the temperature of a tetragonal (T) structural phase transition. For 2000-Angstrom-thick films grown directly on SrTiO3 substrates, a T-->cubic (C) phase transition was found on heating at >950 K, where the lattice constant changed smoothly with temperature. It was also found for films of the same thickness that the T-->C transition is nearly restored to that of bulk crystals by the use of a buffer layer, which relaxes the epitaxial constraint. These results provide evidence of an epitaxially induced high temperature structural phase transition in BaTiO3 thin films, where the ferroelectric (internal) and structural (external) aspects of the phase transition are decoupled. (C) 2004 American Institute of Physics.
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    Multiferroic properties of modified BiFeO3-PbTiO3-based ceramics: Random-field induced release of latent magnetization and polarization
    Wang, Naigang; Cheng, J.; Pyatakov, Alexander P.; Zvezdin, Anatoly Konstantinovich; Li, Jiefang; Cross, L. E.; Viehland, Dwight D. (American Physical Society, 2005-09-28)
    It has been found that aliovalent-substituted BiFeO3-PbTiO3-based polycrystalline materials have significantly enhanced multiferroic properties. Relative to unmodified BiFeO3, our results for modified BiFeO3-PbTiO3-based ceramics reveal: (i) a dramatic increase in the electric-field-induced polarization; and (ii) the establishment of a remanent magnetization. The results evidence the destruction of a space-modulated spin structure in bulk materials, via substituent effects, releasing a latent magnetization locked within the cycloid.
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    A strong magnetoelectric voltage gain effect in magnetostrictive-piezoelectric composite
    Dong, Shuxiang; Li, Jiefang; Viehland, Dwight D.; Cheng, J.; Cross, L. E. (AIP Publishing, 2004-10-01)
    A magnetoelectric laminate composite consisting of magnetostrictive Terfenol-D (Tb1-xDyxFe2-y) and piezoelectric Pb(Zr,Ti)O-3 layers has an extremely high voltage gain effect of approximate to300 at its resonant state, offering potential for high-voltage miniature transformer applications. (C) 2004 American Institute of Physics.