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1.
Adv Mater ; 31(5): e1801949, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30537017

RESUMO

The electrocaloric effect (ECE) refers to reversible thermal changes of a polarizable material upon the application or removal of electric fields. Without a compressor or cooling agents, all-solid-state electrocaloric (EC) refrigeration systems are environmentally benign, highly compact, and of very high energy efficiency. Relaxor ferroelectric ceramics and polymers are promising candidates as EC materials. Here, synergistic efforts are made by composing relaxor Ba(Zr0.21 Ti0.79 )O3 nanofibers with P(VDF-TrFE-CFE) to make relaxor-relaxor-type polymer nanocomposites. The ECEs of the nanocomposites are directly measured and these relaxor nanocomposites exhibit, so far, the highest EC temperature change at a modest electric field, along with high thermal stability within a broad temperature range span to room temperature. The superior EC performance is attributed to the interfacial coupling between dipoles across the filler/polymer interfaces. The thermodynamics and kinetics of interfacial coupling are investigated in situ by piezoresponse force microscopy while the real-time evolution of interfacial coupling is simulated and visualized by phase-field modeling.

2.
Nat Nanotechnol ; 13(10): 972, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30065308

RESUMO

In the version of this Article originally published, the corresponding author names in the author list appeared in the reverse order; they should have read 'Jinxing Zhang and Ce-Wan Nan'. The order of these authors' initials in the 'Correspondence and requests for materials' statement were similarly affected. These errors have now been corrected in all versions of the Article.

3.
Nat Nanotechnol ; 13(10): 947-952, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30038370

RESUMO

Charged domain walls in ferroelectrics exhibit a quasi-two-dimensional conduction path coupled to the surrounding polarization. They have been proposed for use as non-volatile memory with non-destructive operation and ultralow energy consumption. Yet the evolution of domain walls during polarization switching makes it challenging to control their location and conductance precisely, a prerequisite for controlled read-write schemes and for integration in scalable memory devices. Here, we explore and reversibly switch the polarization of square BiFeO3 nanoislands in a self-assembled array. Each island confines cross-shaped, charged domain walls in a centre-type domain. Electrostatic and geometric boundary conditions induce two stable domain configurations: centre-convergent and centre-divergent. We switch the polarization deterministically back and forth between these two states, which alters the domain wall conductance by three orders of magnitude, while the position of the domain wall remains static because of its confinement within the BiFeO3 islands.

4.
Sci Rep ; 6: 27561, 2016 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-27272678

RESUMO

Voltage-driven 180° magnetization switching provides a low-power alternative to current-driven magnetization switching widely used in spintronic devices. Here we computationally demonstrate a promising route to achieve voltage-driven in-plane 180° magnetization switching in a strain-mediated multiferroic heterostructure (e.g., a heterostructure consisting of an amorphous, slightly elliptical Co40Fe40B20 nanomagnet on top of a Pb(Zr,Ti)O3 film as an example). This 180° switching follows a unique precessional path all in the film plane, and is enabled by manipulating magnetization dynamics with fast, local piezostrains (rise/release time <0.1 ns) on the Pb(Zr,Ti)O3 film surface. Our analyses predict ultralow area energy consumption per switching (~0.03 J/m(2)), approximately three orders of magnitude smaller than that dissipated by current-driven magnetization switching. A fast overall switching time of about 2.3 ns is also demonstrated. Further reduction of energy consumption and switching time can be achieved by optimizing the structure and material selection. The present design provides an additional viable route to realizing low-power and high-speed spintronics.

6.
Adv Mater ; 28(2): 363-9, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26540229

RESUMO

The combination of exchange-biased systems and ferroelectric materials offers a simple and effective way to investigate the angular dependence of exchange bias using one sample with electric-field-induced competing anisotropies. A reversible electric-field-controlled magnetization reversal at zero magnetic field is also realized through optimizing the anisotropy configuration, holding promising applications for ultralow power magnetoelectric devices.

7.
Sci Rep ; 5: 10459, 2015 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-25995062

RESUMO

Voltage controlled 180° magnetization reversal has been achieved in BiFeO3-based multiferroic heterostructures, which is promising for the future development of low-power spintronic devices. However, all existing reports involve the use of an in-plane voltage that is unfavorable for practical device applications. Here, we investigate, using phase-field simulations, the out-of-plane (i.e., perpendicular to heterostructures) voltage controlled magnetism in heterostructures consisting of CoFe nanodots and (110) BiFeO3 thin film or island. It is predicted that the in-plane component of the canted magnetic moment at the CoFe/BiFeO3 interface can be reversed repeatedly by applying a perpendicular voltage across the bottom (110) BiFeO3 thin film, which further leads to an in-plane magnetization reversal in the overlaying CoFe nanodot. The non-volatility of such perpendicular voltage controlled magnetization reversal can be achieved by etching the continuous BiFeO3 film into isolated nanoislands with the same in-plane sizes as the CoFe nanodot. The findings would provide general guidelines for future experimental and engineering efforts on developing the electric-field controlled spintronic devices with BiFeO3-based multiferroic heterostructures.

8.
Adv Mater ; 26(41): 7091-5, 2014 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-25213017

RESUMO

The deterministic rotation of magnetization by electric fields is a challenging issue for future low-power spintronics. In a Co/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 multiferroic heterostructure, piezostrain-mediated, macroscopically maneuverable, and non-volatile magnetization reversal without an applied magnetic field is demonstrated. This, combined with the presented phase-field simulations, is of practical relevance for designing prototype devices.

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