P. Warnicke - Academia.edu (original) (raw)
Papers by P. Warnicke
Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnet... more Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films where the cobalt layer is sandwiched between two heavy metals providing additive interfacial Dzyaloshinskii-Moriya interactions, which reach about 2 mJ/m2 in the case of the Ir/Co/Pt multilayers. Using a magnetization-sensitive scanning x-ray transmission microscopy technique, we imaged magnetic bubble-like domains in these multilayers. The study of their behavir in magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the Dzyaloshinsskii-Moriya interaction. This discoevry of stable skyrmions at room temperature in a technologically relevant material opens the way for device applications in a near future.
International audience Facing the ever-growing demand for data storage will most probably require... more International audience Facing the ever-growing demand for data storage will most probably require a new paradigm. Nanoscale magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films where the cobalt layer is sandwiched between two heavy metals providing additive interfacial Dzyaloshinskii-Moriya interactions, which reach a value close to 2 mJ m-2 in the case of the Ir|Co|Pt asymmetric multilayers. Using a magnetization-sensitive scanning x-ray transmission microscopy technique, we imaged small magnetic domains at very low field in these multilayers. The study of their behavior in perpendicular magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the large Dzyaloshinskii-Moriya interaction. This discovery of stable sub-100 nm individual skyrmions at room temperature in a technologically relevant material opens the way ...
Simulations of magnetic microstructure in elliptical Permalloy elements used for controlled motio... more Simulations of magnetic microstructure in elliptical Permalloy elements used for controlled motion of magnetic particles are discussed. The saturating field of the elliptical elements was studied with respect to lateral dimensions for one-vortex, cross-tie, diamond and double-diamond states as initial zero-field domain configurations. With aspect ratio of 1:3 the short axis was varied from 125 nm to 1000 nm, whereas the thickness was kept constant at 50 nm.
Since the beginnings of the electronic age, a quest for ever faster and smaller switches has been... more Since the beginnings of the electronic age, a quest for ever faster and smaller switches has been initiated, since this element is ubiquitous and foundational in any electronic circuit to regulate the flow of current. Mott insulators are promising candidates to meet this need as they undergo extremely fast resistive switching under electric field. However the mechanism of this transition is still under debate. Our spatially-resolved μ-XRD imaging experiments carried out on the prototypal Mott insulator (V0.95Cr0.05)2O3 show that the resistive switching is associated with the creation of a conducting filamentary path consisting in an isostructural compressed phase without any chemical nor symmetry change. This clearly evidences that the resistive switching mechanism is inherited from the bandwidth-controlled Mott transition. This discovery might hence ease the development of a new branch of electronics dubbed Mottronics.
Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnet... more Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films where the cobalt layer is sandwiched between two heavy metals providing additive interfacial Dzyaloshinskii-Moriya interactions, which reach about 2 mJ/m in the case of the Ir|Co|Pt multilayers. Using a magnetization-sensitive scanning x-ray transmission microscopy technique, we imaged magnetic bubble-like domains in these multilayers. The study of their behavior in magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the Dzyaloshinskii-Moriya interaction. This discovery of stable skyrmions at room temperature in a technologically relevant material opens the way for device applications in a near future. A major societal challenge is related to the continually increasing q...
Organic Electronics, 2016
Organic electronics is becoming more and more important because the low level of fabrication and ... more Organic electronics is becoming more and more important because the low level of fabrication and deposition complexity even at large scale makes it a good candidate for future low cost technological product development. P(VDF-TrFE) is a co-polymer of special interest due its ferroelectric property enabling usage in re-programmable non-volatile organic memory and magnetoelectric sensors. Piezo force microscopy (PFM) provides access to the technologically relevant ferroelectric polarisability and its remanent polarization via imaging of the piezoelectric property. Here we use PFM to show that piezoelectric response of a P(VDF-TrFE) film can be enhanced by up to 260 % after soft X-ray irradiation. This enhancement correlates with morphological change of part of the film, from amorphous to crystalline. An optimal irradiation dose is found above which the film gets eroded and the piezoelectric response gets lowered.
Nature Communications, 2016
2015 IEEE Magnetics Conference (INTERMAG), 2015
Magnetic skyrmions are arguably the smallest stable magnetic configuration in films, and therefor... more Magnetic skyrmions are arguably the smallest stable magnetic configuration in films, and therefore could be the ultimate magnetic storage bit. They have also triggered a wide interest due to the new fundamental phenomena related to their topology. Numerical simulations have shown that the interfacial Dzyaloshinskii-Moriya interaction (DMI) can stabilize such skyrmions in nanoscale disks or tracks for a rather large range of DMI amplitudes for which the skyrmion can either be the ground state or metastable relative to the uniform state. Here, we demonstrate experimentally the presence of skyrmions in metallic multilayers structures engineered to exhibit a strong DMI interaction.
Exploring the accessible frequency range of x-ray detected and phase-resolved ferromagnetic reson... more Exploring the accessible frequency range of x-ray detected and phase-resolved ferromagnetic resonance
The sound of seagulls overhead greeted a diverse, international group of expert researchers in ma... more The sound of seagulls overhead greeted a diverse, international group of expert researchers in magnetism as they gathered on the shores of the Long Island Sound in late November. The group assembled on November 21–23, 2010, at Danford's Hotel and Marina in Port Jefferson, NY, USA, to participate in “MXLS10 - A Joint NSLS-II and MAX-lab Workshop: New Opportunities in
Magnetic vortices in nanoscopic ferromagnetic elements can be treated as solitons that exhibit st... more Magnetic vortices in nanoscopic ferromagnetic elements can be treated as solitons that exhibit static and dynamic stability even above room temperature, making them promising for technological applications. Although their properties at low energy configurations have been well studied, the properties of solitons undergoing structural breakdown are poorly understood. Here, we destabilize the soliton through Zeeman and demagnetization interactions and investigate the symmetry breaking of the magnetic vortex state. Using high-resolution Lorentz imaging and numerical simulations, we observe phase transitions of the core from the characteristic point-like structure into distinct extended asymmetric states differentiated by the polarity. The deformations start at intermediate displacements and are traced until the point of annihilation at the disc's edge. We discuss the use of these asymmetric states as a method to determine the core polarity for in-plane magnetic imaging techniques.
Physical Review Letters, 2006
Physical Review Letters, 2008
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
Physical Review B, 2008
A magnetic vortex domain wall, confined in a Permalloy nanowire with periodically varying width, ... more A magnetic vortex domain wall, confined in a Permalloy nanowire with periodically varying width, is brought to resonance and long-range motion by means of a spin-polarized alternating current in micromagnetical simulations. The long-range direction of motion is found to be ...
Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnet... more Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films where the cobalt layer is sandwiched between two heavy metals providing additive interfacial Dzyaloshinskii-Moriya interactions, which reach about 2 mJ/m2 in the case of the Ir/Co/Pt multilayers. Using a magnetization-sensitive scanning x-ray transmission microscopy technique, we imaged magnetic bubble-like domains in these multilayers. The study of their behavir in magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the Dzyaloshinsskii-Moriya interaction. This discoevry of stable skyrmions at room temperature in a technologically relevant material opens the way for device applications in a near future.
International audience Facing the ever-growing demand for data storage will most probably require... more International audience Facing the ever-growing demand for data storage will most probably require a new paradigm. Nanoscale magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films where the cobalt layer is sandwiched between two heavy metals providing additive interfacial Dzyaloshinskii-Moriya interactions, which reach a value close to 2 mJ m-2 in the case of the Ir|Co|Pt asymmetric multilayers. Using a magnetization-sensitive scanning x-ray transmission microscopy technique, we imaged small magnetic domains at very low field in these multilayers. The study of their behavior in perpendicular magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the large Dzyaloshinskii-Moriya interaction. This discovery of stable sub-100 nm individual skyrmions at room temperature in a technologically relevant material opens the way ...
Simulations of magnetic microstructure in elliptical Permalloy elements used for controlled motio... more Simulations of magnetic microstructure in elliptical Permalloy elements used for controlled motion of magnetic particles are discussed. The saturating field of the elliptical elements was studied with respect to lateral dimensions for one-vortex, cross-tie, diamond and double-diamond states as initial zero-field domain configurations. With aspect ratio of 1:3 the short axis was varied from 125 nm to 1000 nm, whereas the thickness was kept constant at 50 nm.
Since the beginnings of the electronic age, a quest for ever faster and smaller switches has been... more Since the beginnings of the electronic age, a quest for ever faster and smaller switches has been initiated, since this element is ubiquitous and foundational in any electronic circuit to regulate the flow of current. Mott insulators are promising candidates to meet this need as they undergo extremely fast resistive switching under electric field. However the mechanism of this transition is still under debate. Our spatially-resolved μ-XRD imaging experiments carried out on the prototypal Mott insulator (V0.95Cr0.05)2O3 show that the resistive switching is associated with the creation of a conducting filamentary path consisting in an isostructural compressed phase without any chemical nor symmetry change. This clearly evidences that the resistive switching mechanism is inherited from the bandwidth-controlled Mott transition. This discovery might hence ease the development of a new branch of electronics dubbed Mottronics.
Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnet... more Facing the ever-growing demand for data storage will most probably require a new paradigm. Magnetic skyrmions are anticipated to solve this issue as they are arguably the smallest spin textures in magnetic thin films in nature. We designed cobalt-based multilayered thin films where the cobalt layer is sandwiched between two heavy metals providing additive interfacial Dzyaloshinskii-Moriya interactions, which reach about 2 mJ/m in the case of the Ir|Co|Pt multilayers. Using a magnetization-sensitive scanning x-ray transmission microscopy technique, we imaged magnetic bubble-like domains in these multilayers. The study of their behavior in magnetic field allows us to conclude that they are actually magnetic skyrmions stabilized by the Dzyaloshinskii-Moriya interaction. This discovery of stable skyrmions at room temperature in a technologically relevant material opens the way for device applications in a near future. A major societal challenge is related to the continually increasing q...
Organic Electronics, 2016
Organic electronics is becoming more and more important because the low level of fabrication and ... more Organic electronics is becoming more and more important because the low level of fabrication and deposition complexity even at large scale makes it a good candidate for future low cost technological product development. P(VDF-TrFE) is a co-polymer of special interest due its ferroelectric property enabling usage in re-programmable non-volatile organic memory and magnetoelectric sensors. Piezo force microscopy (PFM) provides access to the technologically relevant ferroelectric polarisability and its remanent polarization via imaging of the piezoelectric property. Here we use PFM to show that piezoelectric response of a P(VDF-TrFE) film can be enhanced by up to 260 % after soft X-ray irradiation. This enhancement correlates with morphological change of part of the film, from amorphous to crystalline. An optimal irradiation dose is found above which the film gets eroded and the piezoelectric response gets lowered.
Nature Communications, 2016
2015 IEEE Magnetics Conference (INTERMAG), 2015
Magnetic skyrmions are arguably the smallest stable magnetic configuration in films, and therefor... more Magnetic skyrmions are arguably the smallest stable magnetic configuration in films, and therefore could be the ultimate magnetic storage bit. They have also triggered a wide interest due to the new fundamental phenomena related to their topology. Numerical simulations have shown that the interfacial Dzyaloshinskii-Moriya interaction (DMI) can stabilize such skyrmions in nanoscale disks or tracks for a rather large range of DMI amplitudes for which the skyrmion can either be the ground state or metastable relative to the uniform state. Here, we demonstrate experimentally the presence of skyrmions in metallic multilayers structures engineered to exhibit a strong DMI interaction.
Exploring the accessible frequency range of x-ray detected and phase-resolved ferromagnetic reson... more Exploring the accessible frequency range of x-ray detected and phase-resolved ferromagnetic resonance
The sound of seagulls overhead greeted a diverse, international group of expert researchers in ma... more The sound of seagulls overhead greeted a diverse, international group of expert researchers in magnetism as they gathered on the shores of the Long Island Sound in late November. The group assembled on November 21–23, 2010, at Danford's Hotel and Marina in Port Jefferson, NY, USA, to participate in “MXLS10 - A Joint NSLS-II and MAX-lab Workshop: New Opportunities in
Magnetic vortices in nanoscopic ferromagnetic elements can be treated as solitons that exhibit st... more Magnetic vortices in nanoscopic ferromagnetic elements can be treated as solitons that exhibit static and dynamic stability even above room temperature, making them promising for technological applications. Although their properties at low energy configurations have been well studied, the properties of solitons undergoing structural breakdown are poorly understood. Here, we destabilize the soliton through Zeeman and demagnetization interactions and investigate the symmetry breaking of the magnetic vortex state. Using high-resolution Lorentz imaging and numerical simulations, we observe phase transitions of the core from the characteristic point-like structure into distinct extended asymmetric states differentiated by the polarity. The deformations start at intermediate displacements and are traced until the point of annihilation at the disc's edge. We discuss the use of these asymmetric states as a method to determine the core polarity for in-plane magnetic imaging techniques.
Physical Review Letters, 2006
Physical Review Letters, 2008
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
Physical Review B, 2008
A magnetic vortex domain wall, confined in a Permalloy nanowire with periodically varying width, ... more A magnetic vortex domain wall, confined in a Permalloy nanowire with periodically varying width, is brought to resonance and long-range motion by means of a spin-polarized alternating current in micromagnetical simulations. The long-range direction of motion is found to be ...