Category: News

Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound

Magnetic nano-objects, namely antiskyrmions and Bloch skyrmions, have been found to coexist in single-crystalline lamellae formed from bulk crystals of inverse tetragonal Heusler compounds with D2d symmetry. *

Skyrmions can be observed in real-space by various direct imaging techniques. *

In the article “Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound”  Ankit K. Sharma, Jagannath Jena, Kumari Gaurav Rana, Anastasios Markou, Holger L. Meyerheim, Katayoon Mohseni, Abhay K. Srivastava, Ilya Kostanoskiy, Claudia Felser and Stuart S. P. Parkin  describe the use of magnetic force microscopy (MFM) imaging to investigate magnetic textures in epitaxial thin films of [001]-oriented Mn2RhSn formed by magnetron sputtering.*

They find evidence for magnetic nano-objects which exhibit a wide range of sizes with stability with respect to magnetic field and temperature that is similar to single-crystalline lamellae. *

However, the nano-objects do not form well-defined arrays, nor is any evidence found for helical spin textures. This is speculated to likely be a consequence of the poorer homogeneity of chemical ordering in the thin films. *

Evidence is found for elliptically distorted nano-objects along perpendicular crystallographic directions within the epitaxial films, which is consistent with elliptical Bloch skyrmions observed in single-crystalline lamellae. Thus, these measurements provide strong evidence for the formation of noncollinear spin textures in thin films of Mn2RhSn. *

Using these films, it is shown that individual nano-objects can be deleted using a local magnetic field from a magnetic AFM tip and collections of nano-objects can be similarly written. *

For writing and deleting the nano-objects, magnetic AFM probes from NanoWorld of the Pointprobe® MFMR type were used. *

These observations described in the article suggest a path toward the use of these nano-objects in thin films with D2d symmetry as magnetic memory elements paving the way to the realization of skyrmionic devices based on Heusler thin films. *

Figure 5 from Ankit K. Sharma et al. Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound : Controlled creation and annihilation of nano-objects in a 35 nm-thick Mn2RhSn thin film. a) Schematic illustration of magnetization orientations of MFM tip and sample for writing. The distance between tip and the sample is the scan height z. b–e) MFM images in zero field and z = 80, 40, 30, and 20 nm, respectively at 200 K. f) Contact-mode image in zero field and 200 K. The blue and red colors represent up and down magnetization, respectively. Images in (b)–(f) are at the same scale: a scale bar is given in (f). g–i) MFM images taken at z = 70, 50, and 30 nm at 100 K under Hz = 180 mT. Images in (g)–(i) are at the same scale: a scale bar is given in (i). For writing and deleting the nano-objects, magnetic AFM probes from NanoWorld of the Pointprobe® MFMR type were used.
Figure 5 from Ankit K. Sharma et al. Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound :
Controlled creation and annihilation of nano-objects in a 35 nm-thick Mn2RhSn thin film. a) Schematic illustration of magnetization orientations of MFM tip and sample for writing. The distance between tip and the sample is the scan height z. b–e) MFM images in zero field and z = 80, 40, 30, and 20 nm, respectively at 200 K. f) Contact-mode image in zero field and 200 K. The blue and red colors represent up and down magnetization, respectively. Images in (b)–(f) are at the same scale: a scale bar is given in (f). g–i) MFM images taken at z = 70, 50, and 30 nm at 100 K under Hz = 180 mT. Images in (g)–(i) are at the same scale: a scale bar is given in (i).

*Ankit K. Sharma, Jagannath Jena, Kumari Gaurav Rana, Anastasios Markou, Holger L. Meyerheim, Katayoon Mohseni, Abhay K. Srivastava, Ilya Kostanoskiy, Claudia Felser, Stuart S. P. Parkin
Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound
Advanced Materials, Volume 33, Issue 32, August 12, 2021, 2101323
DOI: https://doi.org/10.1002/adma.202101323

Open Access The article “Nanoscale Noncollinear Spin Textures in Thin Films of a D2d Heusler Compound” Ankit K. Sharma, Jagannath Jena, Kumari Gaurav Rana, Anastasios Markou, Holger L. Meyerheim, Katayoon Mohseni, Abhay K. Srivastava, Ilya Kostanoskiy, Claudia Felser and Stuart S. P. Parkin is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Electrochemically Synthesized Poly(3-hexylthiophene) Nanowires as Photosensitive Neuronal Interfaces

Poly(3-hexylthiophene) (P3HT), a hole-conducting polymer, generates a lot of interest especially because of its excellent optoelectronic properties (such as good electrical conductivity and high extinction coefficient) and good processability, which make this polymer an excellent choice for building organic optoelectronic devices (e.g., organic solar cells). *

P3HT films and nanoparticles have also been used to restore the photosensitivity of retinal neurons. *

For their article “Electrochemically Synthesized Poly(3-hexylthiophene) Nanowires as Photosensitive Neuronal Interfaces” Szilveszter Gáspár, Tiziana Ravasenga, Raluca-Elena Munteanu, Sorin David, Fabio Benfenati, and Elisabetta Colombo investigated the template-assisted electrochemical synthesis of P3HT nanowires doped with tetrabutylammonium hexafluorophosphate (TBAHFP) and their biocompatibility with primary neurons. *

They were able to show that template-assisted electrochemical synthesis can relatively easily turn 3-hexylthiophene (3HT) into longer (e.g., 17 ± 3 µm) or shorter (e.g., 1.5 ± 0.4 µm) P3HT nanowires with an average diameter of 196 ± 55 nm (determined by the used template) and that the nanowires produce measurable photocurrents following illumination. *

The fact that template-assisted electrochemical synthesis combines polymerization, doping, and polymer nanostructuring into one, relatively simple step is the most important advantage of this method. The possibility of easily tuning the length of the produced nanowires represents another important advantage. *

The authors were also able to demonstrate that primary cortical neurons can be grown onto P3HT nanowires drop-casted on a glass substrate without relevant changes in their viability and electrophysiological properties, indicating that P3HT nanowires obtained by template-assisted electrochemical synthesis represent a promising neuronal interface for photostimulation. *

Szilveszter Gáspár  et al. proved the biocompability of the obtained P3HT nanowires upon incubation for different periods with primary neuronal cultures. They demonstrated that their presence does not affect the membrane properties of the neurons or the excitability of the neurons as evaluated by patch-clamp experiments. These results show the potential of the described synthesis methodology to fabricate injectable P3HT-based photosensitive nanowires with high biocompatibility, ultimately paving the way for their exploitation for neuronal photostimulation. *

Atomic Force Microscopy (AFM) was used to characterize P3HT nanowires drop-casted onto glass coverslips. *

The Atomic Force Microscopy images were obtained in air and in intermittent contact-mode using line rates as slow as 0.2 Hz and NanoWorld Pointprobe® NCSTR silicon soft-tapping AFM probes (typical values: resonant frequency 160 kHz, force constant 7.2 N m). The ratio between the set-point amplitude and the free amplitude of the AFM cantilever was set to 0.5–0.6. The obtained AFM images were used to determine both the lengths and the diameters of the nanowires. *

Figure 3 from “Electrochemically Synthesized Poly(3-hexylthiophene) Nanowires as Photosensitive Neuronal Interfaces” by Szilveszter Gáspár et al.: AFM images of “long” P3HT nanowires (A) and of “short” P3HT nanowires (B). NanoWorld Pointprobe NCSTR soft-tapping mode probes were used.
Figure 3 from “Electrochemically Synthesized Poly(3-hexylthiophene) Nanowires as Photosensitive Neuronal Interfaces” by Szilveszter Gáspár et al.:
AFM images of “long” P3HT nanowires (A) and of “short” P3HT nanowires (B).

*Szilveszter Gáspár, Tiziana Ravasenga, Raluca-Elena Munteanu, Sorin David, Fabio Benfenati, and Elisabetta Colombo
Electrochemically Synthesized Poly(3-hexylthiophene) Nanowires as Photosensitive Neuronal Interfaces
Materials 2021, 14(16), 4761, Special Issue Advanced Designs of Materials, Devices and Techniques for Biosensing
DOI: https://doi.org/10.3390/ma14164761 (please follow this external link to read the full article.)

Open Access The article “Electrochemically Synthesized Poly(3-hexylthiophene) Nanowires as Photosensitive Neuronal Interfaces” by Szilveszter Gáspár, Tiziana Ravasenga, Raluca-Elena Munteanu, Sorin David, Fabio Benfenati, and Elisabetta Colombo is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.