Browsing by Author "Martin, Lane W."

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Complex strain evolution of polar and magnetic order in multiferroic BiFeO3 thin films
(2018-09-21)
Chen, Zuhuang
;
Chen, Zhanghui
;
Kuo, Chang-Yang
;
Tang, Yunlong
;
Dedon, Liv R.
Electric-field control of magnetism requires deterministic control of the magnetic order and understanding of the magnetoelectric coupling in multiferroics like BiFeO3 and EuTiO3. Despite this critical need, there are few studies on the strain evolution of magnetic order in BiFeO3 films. Here, in (110)-oriented BiFeO3 films, we reveal that while the polarization structure remains relatively unaffected, strain can continuously tune the orientation of the antiferromagnetic-spin axis across a wide angular space, resulting in an unexpected deviation of the classical perpendicular relationship between the antiferromagnetic axis and the polarization. Calculations suggest that this evolution arises from a competition between the Dzyaloshinskii-Moriya interaction and single-ion anisotropy wherein the former dominates at small strains and the two are comparable at large strains. Finally, strong coupling between the BiFeO3 and the ferromagnet Co0.9Fe0.1 exists such that the magnetic anisotropy of the ferromagnet can be effectively controlled by engineering the orientation of the antiferromagnetic-spin axis.
Direct Observation of Capacitor Switching Using Planar Electrodes
(2010-10-22)
Balke, Nina
;
Gajek, Martin
;
Tagantsev, Alexander K.
;
Martin, Lane W.
;
Chu, Ying-Hao
Ferroelectric polarization switching in epitaxial (110) BiFeO(3) films is studied using piezoresponse force microscopy of a model in-plane capacitor structure. The electrode orientation is chosen such that only two active domain variants exist. Studies of the kinetics of domain evolution allows clear visualization of nucleation sites, as well as forward and lateral growth stages of domain formation. It is found that the location of the reverse-domain nucleation is correlated with the direction of switching in a way that the polarization in the domains nucleated at an electrode is always directed away from it. The role of interface charge injection and surface screening charge on switching mechanisms is explored, and the nucleation is shown to be controllable by the bias history of the sample. Finally, the manipulation of domain nucleation through domain structure engineering is illustrated. These studies pave the way for the engineering and design of the ferroelectric device structures through control of individual steps of the switching process.
Manipulating magnetoelectric energy landscape in multiferroics
(2020-06-05)
Huang, Yen-Lin
;
Nikonov, Dmitri
;
Addiego, Christopher
;
Chopdekar, Rajesh, V
;
Prasad, Bhagwati
Magnetoelectric coupling at room temperature in multiferroic materials, such as BiFeO3, is one of the leading candidates to develop low-power spintronics and emerging memory technologies. Although extensive research activity has been devoted recently to exploring the physical properties, especially focusing on ferroelectricity and antiferromagnetism in chemically modified BiFeO3, a concrete understanding of the magnetoelectric coupling is yet to be fulfilled. We have discovered that La substitutions at the Bi-site lead to a progressive increase in the degeneracy of the potential energy landscape of the BiFeO3 system exemplified by a rotation of the polar axis away from the < 111 > (pc) towards the < 112 > (pc) discretion. This is accompanied by corresponding rotation of the antiferromagnetic axis as well, thus maintaining the right-handed vectorial relationship between ferroelectric polarization, antiferromagnetic vector and the Dzyaloshinskii-Moriya vector. As a consequence, La-BiFeO3 films exhibit a magnetoelectric coupling that is distinctly different from the undoped BiFeO3 films. BiFeO3 has a wide application but the impact of rare-earth substitution for the evolution of the coupling mechanism is unknown. Here, the authors reveal the correlation between ferroelectricity, antiferromagnetism, a weak ferromagnetic moment, and their switching pathways in La-substituted BiFeO3.
Nanoscale Control of Domain Architectures in BiFeO(3) Thin Films
(2009-04-01)
Chu, Ying-Hao
;
He, Qing
;
Yang, Chan-Ho
;
Yu, Pu
;
Martin, Lane W.
We demonstrate an approach to create a one-dimensional nanoscale array of domain walls in epitaxial La-substituted BiFeO(3) films. We have used a DySCO(3) (110)(o) single-crystal substrate to provide an anisotropic strain to exclude two of the possible structural variants. Furthermore, through careful control of electrostatic boundary conditions, such as the thickness of the SrRuO(3) bottom electrode to induce the self-poling effects, we can choose to obtain either 1090 or 710 one-dimensional periodic domain walls. Detailed measurements of the domain structures is shown using piezoresponse force microscopy and X-ray diffraction, which confirms that these periodic structures are the same as those suggested in previous literature.
Nanoscale Control of Domain Architectures in BiFeO3 Thin Films
(2009-04-01)
Chu, Ying-Hao
;
He, Qing
;
Yang, Chan-Ho
;
Yu, Pu
;
Martin, Lane W.
We demonstrate an approach to create a one-dimensional nanoscale array of domain walls in epitaxial La-substituted BiFeO3 films. We have used a DySCO3 (110)(o) single-crystal substrate to provide an anisotropic strain to exclude two of the possible structural variants. Furthermore, through careful control of electrostatic boundary conditions, such as the thickness of the SrRuO3 bottom electrode to induce the self-poling effects, we can choose to obtain either 1090 or 710 one-dimensional periodic domain walls. Detailed measurements of the domain structures is shown using piezoresponse force microscopy and X-ray diffraction, which confirms that these periodic structures are the same as those suggested in previous literature.
Nanoscale Structure and Mechanism for Enhanced Electromechanical Response of Highly Strained BiFeO(3) Thin Films
(2011-07-26)
Damodaran, Anoop R.
;
Liang, Chen-Wei
;
He, Qing
;
Peng, Chun-Yen
;
Chang, Li
The presence of a variety of structural variants in BiFeO(3) thin films give rise to exotic electric-field-induced responses and resulting electromechanical responses as large as 5%. Using high-resolution X-ray diffraction and scanning-probe-microscopy-based studies the numerous phases present at the phase boundaries are identified and an intermediate monoclinic phase, in addition to the previously observed rhombohedral- and tetragonal-like phases, is discovered.
Nanoscale Structure and Mechanism for Enhanced Electromechanical Response of Highly Strained BiFeO3 Thin Films
(2011-07-26)
Damodaran, Anoop R.
;
Liang, Chen-Wei
;
He, Qing
;
Peng, Chun-Yen
;
Chang, Li
The presence of a variety of structural variants in BiFeO3 thin films give rise to exotic electric-field-induced responses and resulting electromechanical responses as large as 5%. Using high-resolution X-ray diffraction and scanning-probe-microscopy-based studies the numerous phases present at the phase boundaries are identified and an intermediate monoclinic phase, in addition to the previously observed rhombohedral- and tetragonal-like phases, is discovered.
Switching kinetics in epitaxial BiFeO(3) thin films
(2010-04-15)
Pantel, Daniel
;
Chu, Ying-Hao
;
Martin, Lane W.
;
Ramesh, Ramamoorthy
;
Hesse, Dietrich
The switching kinetics in epitaxial (001)-, (110)-, and (111)-oriented BiFeO(3) thin films were investigated as a function of applied field and time. It was found that the ferroelectric switching behavior obeys the Kolmogorov-Avrami-Ishibashi theory only in the high field range. The detailed behavior depends on the film orientation. A comparison with standard systems, such as epitaxial Pb(Zr(0.2)Ti(0.8))O(3) films, reveals some similarities as well as some differences. For instance, the presence of 109 degrees and 71 degrees ferroelastic domain walls might be ruled out as the source of the decrease in switched polarization at low applied fields, in contrast to what is the case for a/c domain walls in tetragonal Pb(Zr(0.2)Ti(0.8))O(3). (C) 2010 American Institute of Physics. [doi:10.1063/1.3392884]
Switching kinetics in epitaxial BiFeO3 thin films
(2010-04-15)
Pantel, Daniel
;
Chu, Ying-Hao
;
Martin, Lane W.
;
Ramesh, Ramamoorthy
;
Hesse, Dietrich
The switching kinetics in epitaxial (001)-, (110)-, and (111)-oriented BiFeO3 thin films were investigated as a function of applied field and time. It was found that the ferroelectric switching behavior obeys the Kolmogorov-Avrami-Ishibashi theory only in the high field range. The detailed behavior depends on the film orientation. A comparison with standard systems, such as epitaxial Pb(Zr0.2Ti0.8)O-3 films, reveals some similarities as well as some differences. For instance, the presence of 109 degrees and 71 degrees ferroelastic domain walls might be ruled out as the source of the decrease in switched polarization at low applied fields, in contrast to what is the case for a/c domain walls in tetragonal Pb(Zr0.2Ti0.8)O-3. (C) 2010 American Institute of Physics. [doi:10.1063/1.3392884]