Browsing by Author "Jesse, S."

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Controlling magnetoelectric coupling by nanoscale phase transformation in strain engineered bismuth ferrite
(2012)
Liu, Y. Y.
;
Vasudevan, R. K.
;
Pan, K.
;
Xie, S. H.
;
Liang, W-I
The magnetoelectric coupling in multiferroic materials is promising for a wide range of applications, yet manipulating magnetic ordering by electric field proves elusive to obtain and difficult to control. In this paper, we explore the prospect of controlling magnetic ordering in misfit strained bismuth ferrite (BiFeO3, BFO) films, combining theoretical analysis, numerical simulations, and experimental characterizations. Electric field induced transformation from a tetragonal phase to a distorted rhombohedral one in strain engineered BFO films has been identified by thermodynamic analysis, and realized by scanning probe microscopy (SPM) experiment. By breaking the rotational symmetry of a tip-induced electric field as suggested by phase field simulation, the morphology of distorted rhombohedral variants has been delicately controlled and regulated. Such capabilities enable nanoscale control of magnetoelectric coupling in strain engineered BFO films that is difficult to achieve otherwise, as demonstrated by phase field simulations.
Deterministic control of ferroelastic switching in multiferroic materials
(2009-12-01)
Balke, N.
;
Choudhury, S.
;
Jesse, S.
;
Huijben, M.
;
Chu, Y. H.
Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.
Role of measurement voltage on hysteresis loop shape in Piezoresponse Force Microscopy
(2012-11-05)
Strelcov, E.
;
Kim, Y.
;
Yang, J. C.
;
Chu, Y. H.
;
Yu, P.
The dependence of field-on and field-off hysteresis loop shape in Piezoresponse Force Microscopy (PFM) on driving voltage, V-ac, is explored. A nontrivial dependence of hysteresis loop parameters on measurement conditions is observed. The strategies to distinguish between paraelectric and ferroelectric states with small coercive bias and separate reversible hysteretic and non-hysteretic behaviors are suggested. Generally, measurement of loop evolution with V-ac is a necessary step to establish the veracity of PFM hysteresis measurements. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764939]
Single-domain multiferroic BiFeO3 films
(2016-09-01)
Kuo, C. -Y.
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Hu, Z.
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Yang, J. C.
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Liao, S. -C.
;
Huang, Y. L.
The strong coupling between antiferromagnetism and ferroelectricity at room temperature found in BiFeO3 generates high expectations for the design and development of technological devices with novel functionalities. However, the multi-domain nature of the material tends to nullify the properties of interest and complicates the thorough understanding of the mechanisms that are responsible for those properties. Here we report the realization of a BiFeO3 material in thin film form with single-domain behaviour in both its magnetism and ferroelectricity: the entire film shows its antiferromagnetic axis aligned along the crystallographic b axis and its ferroelectric polarization along the c axis. With this we are able to reveal that the canted ferromagnetic moment due to the Dzyaloshinskii-Moriya interaction is parallel to the a axis. Furthermore, by fabricating a Co/BiFeO3 heterostructure, we demonstrate that the ferromagnetic moment of the Co film does couple directly to the canted moment of BiFeO3.
Unraveling the origins of electromechanical response in mixed-phase bismuth ferrite
(2013-07-08)
Vasudevan, R. K.
;
Okatan, M. B.
;
Liu, Y. Y.
;
Jesse, S.
;
Yang, J. -C.
The origin of giant electromechanical response in a mixed-phase rhombohedral-tetragonal BiFeO3 thin film is probed using subcoercive scanning probe microscopy based multiple-harmonic measurements. Significant contributions to the strain arise from a second-order harmonic response localized at the phase boundaries. Strain and dissipation data, backed by thermodynamic calculations, suggest that the source of the enhanced electromechanical response is the motion of phase boundaries. These findings elucidate the key role of labile phase boundaries, both natural and artificial, in achieving thin films with giant electromechanical properties.