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Full-Text Articles in Physics

Microscopic Origins Of The Large Piezoelectricity Of Leadfree (Ba,Ca)(Zr,Ti)O3, Yousra Nahas, Alireza Akbarzadeh, Sergei Prokhorenko, Sergey Prosandeev, Raymond Walter, Igor Kornev, Jorgé Íñiguez, Laurent Bellaiche Jun 2017

Microscopic Origins Of The Large Piezoelectricity Of Leadfree (Ba,Ca)(Zr,Ti)O3, Yousra Nahas, Alireza Akbarzadeh, Sergei Prokhorenko, Sergey Prosandeev, Raymond Walter, Igor Kornev, Jorgé Íñiguez, Laurent Bellaiche

Raymond Walter

In light of directives around the world to eliminate toxic materials in various technologies, finding lead-free materials with high piezoelectric responses constitutes an important current scientific goal. As such, the recent discovery of a large electromechanical conversion near room temperature in (1 x)Ba(Zr0.2Ti0.8)O3 x(Ba0.7Ca0.3)TiO3 compounds has directed attention to understanding its origin. Here, we report the development of a large-scale atomistic scheme providing a microscopic insight into this technologically promising material. We find that its high piezoelectricity originates from the existence of large ...


Toy Model For Uncommon Spin–Orbit-Driven Spin-Torque Terms .Pdf, Raymond Walter, Charles Paillard, Surendra Singh, Brahim Dkhil, Laurent Bellaiche May 2017

Toy Model For Uncommon Spin–Orbit-Driven Spin-Torque Terms .Pdf, Raymond Walter, Charles Paillard, Surendra Singh, Brahim Dkhil, Laurent Bellaiche

Raymond Walter

A toy model combining the angular magneto electric (AME) coupling Hamitonian (Mondal et al 2015 Phys. Rev. B 92 100402) with long-range magnetic dipolar interactions is used
to investigate spin-torque phenomena in a magnetic spin valve. It is found that such model (1) gives rise to spin-torque expressions that are analogous in form to those of the common spin-transfer torques; but also (2) predicts additional spin-torque terms, which are generated by an electrical current oriented along unconventional, in-plane directions. The magnitude of the AME induced terms is estimated and the conditions under which they may contribute signi cantly are explored. 


Electrical Control Of Chiral Phases In Electrotoroidic Nanocomposites, Raymond T. Walter, Sergei Prokhorenko, Zhigang Gui, Yousra Nahas, Laurent Bellaiche Jan 2016

Electrical Control Of Chiral Phases In Electrotoroidic Nanocomposites, Raymond T. Walter, Sergei Prokhorenko, Zhigang Gui, Yousra Nahas, Laurent Bellaiche

Raymond Walter

Molecular dynamics in a first-principle-based effective Hamiltonian scheme show that optical rotation of polarized light as measured by gyrotropic coefficient is maximized at room temperature for some applied DC electric field in a ferroelectric nanocomposite consisting of BaTiO3 nanowires in an SrTiO3 medium that exhibits electrical vortices. Together with a phase diagram obtained from Monte Carlo simulation, this characterizes optical applications of electrical vortices.


Electrical Control Of Chiral Phases In Electrotoroidicnanocomposites, Raymond Walter, Sergei Prokhorenko, Zhigang Gui, Yousra Nahas, Laurent Bellaiche Dec 2015

Electrical Control Of Chiral Phases In Electrotoroidicnanocomposites, Raymond Walter, Sergei Prokhorenko, Zhigang Gui, Yousra Nahas, Laurent Bellaiche

Raymond Walter

Molecular dynamics in a first-principle-based effective Hamiltonian scheme show that optical rotation of polarized light as measured by gyrotropic coefficient is maximized at room temperature for some applied DC electric field in a ferroelectric nanocomposite consisting of BaTiO3nanowires in an SrTiO3 medium that exhibits electrical vortices. Together with a phase diagram obtained from Monte Carlo simulation, this characterizes optical applications of electrical vortices.


Revisiting Galvanomagnetic Effects In Conducting Ferromagnets, Raymond Walter, Michel Viret, Surendra Singh, Laurent Bellaiche Dec 2015

Revisiting Galvanomagnetic Effects In Conducting Ferromagnets, Raymond Walter, Michel Viret, Surendra Singh, Laurent Bellaiche

Raymond Walter

The recently proposed coupling between the angular momentum density and magnetic moments is shown
to provide a straightforward alternative explanation for galvanomagnetic eects, i.e., for both anisotropic
magnetoresistance (AMR) and planar Hall eect (PHE). Such coupling naturally reproduces the general
formula associated with AMR and PHE and allows for the occurrence of so-called `negative AMR'. This
coupling also provides a unifying link between AMR, PHE and the anomalous Hall eect (AHE) since this
same coupling was previously found to give rise to AHE (Bellaiche et al 2013 Phys. Rev. B 88 161102).


Revisiting Galvanomagnetic Effects In Conducting Ferromagnets, Raymond T. Walter, Michel Viret, Surendra Singh, Laurent Bellaiche Oct 2014

Revisiting Galvanomagnetic Effects In Conducting Ferromagnets, Raymond T. Walter, Michel Viret, Surendra Singh, Laurent Bellaiche

Raymond Walter

 The recently proposed coupling between the angular momentum density and magnetic
moments is shown to provide a straightforward alternative explanation for galvanomagnetic
effects, i.e. for both anisotropic magnetoresistance (AMR) and planar Hall effect (PHE). Such
coupling naturally reproduces the general formula associated with AMR and PHE and allows
for the occurrence of so-called ‘negative AMR’. This coupling also provides a unifying link
between AMR, PHE and the anomalous Hall effect (AHE) since this same coupling was
previously found to give rise to AHE (Bellaiche et al  2013 Phys. Rev.  B 88 161102 ).


Modeling Complex Properties Of Ferroelectric Nanocomposites, Raymond T. Walter Apr 2013

Modeling Complex Properties Of Ferroelectric Nanocomposites, Raymond T. Walter

Raymond Walter

No abstract provided.