Influence of magnetic domain walls on all-optical magnetic toggle switching in a ferrimagnetic GdFe film

We present a microscopic magnetic domain imaging study of single-shot all-optical magnetic toggle switching of a ferrimagnetic Gd(26)Fe(74) film with out-of-plane easy axis of magnetization by X-ray magnetic circular dichroism photoelectron emission microscopy. Individual linearly polarized laser pulses of 800 nm wavelength and 100 fs duration above a certain threshold fluence reverse the sample magnetization, independent of the magnetization direction, the so-called toggle switching. Local deviations from this deterministic behavior close to magnetic domain walls are studied in detail. Reasons for nondeterministic toggle switching are related to extrinsic effects, caused by pulse-to-pulse variations of the exciting laser system, and to intrinsic effects related to the magnetic domain structure of the sample. The latter are, on the one hand, caused by magnetic domain wall elasticity, which leads to a reduction of the domain-wall length at features with sharp tips. These features appear after the optical switching at positions where the line of constant threshold fluence in the Gaussian footprint of the laser pulse comes close to an already existing domain wall. On the other hand, we identify the presence of laser-induced domain-wall motion in the toggle-switching event as a further cause for local deviations from purely deterministic toggle switching

Ultrafast laser-induced magneto-optical changes in resonant magnetic x-ray reflectivity

We investigate the magneto-optical response of Co to an ultrashort laser excitation by x-ray resonant magnetic reflectivity (XRMR) employing circular polarization. The time-resolved reflectivities detected for opposite sample magnetization are separated into magnetic and nonmagnetic contributions, which contain information about the structural, electronic, and magnetic properties of the sample. Different response times of the different contributions are observed. The experimental results are reproduced numerically by two different simulation approaches. On the one hand, we use a purely thermal model, a time-dependent heat-induced loss of macroscopic magnetization, and an inhomogeneous laser-induced strain profile. On the other hand, we employ time-dependent density-functional theory to calculate the transient optical response to the laser-induced excitation and from that the reflected intensities. While both methods are able to reproduce the time dependence of the magnetic signal, the ultrafast nonmagnetic change in reflectivity is captured satisfactorily only in simulations of the transient optical response function and has thus to be assigned to electronic effects. The energy dependence of the magnetic circular dichroism is investigated in the simulations, highlighting a dependence of the observable on the probing energy. Finally, a phenomenological explanation of the dynamics measured in dichroic x-ray reflectivity in the different channels is offered

Thermal- and Light-Induced Spin-Crossover Characteristics of a Functional Iron(II) Complex at Submonolayer Coverage on HOPG

Studies on the spin-state switching characteristics of surface-bound thin films of spin-crossover (SCO) complexes are of interest to harness the device utility of the SCO complexes. Molecule–substrate interactions govern the SCO of surface-bound films in direct contact with the underlying substrates. In this study, we elucidate the role of molecule–substrate interactions on the thermal- and light-induced spin-state switching characteristics of a functional SCO-complex—[Fe(H2B(pz)2)2COOC12H25-bipy] (pz = pyrazole, C12-bpy = dodecyl[2,2′-bipyridine]-5-carboxylate) deposited at a submonolayer coverage on a highly oriented pyrolytic graphite (HOPG) substrate. A spin-state coexistence of 42% low-spin (LS) and 58% high-spin (HS) is observed for the 0.4 ML deposit of the complex at 40 K, in contrast to the complete spin-state switching observed in the bulk and in SiOx-bound 10 nm thick films. Cooling the sample to 10 K results in a decrease of the LS fraction to 36%, attributed to soft-X-ray-induced excited spin-state trapping (SOXIESST). Illumination of the sample with a green light (λ = 520 nm) at 10 K caused the LS-to-HS switching of the remaining (36%) LS complexes, by a process termed light-induced excited spin-state trapping (LIESST). The mixed spin-state in the submonolayer coverage of [Fe(H2B(pz)2)2COOC12H25-bipy] highlights the role of molecule–HOPG substrate interactions in tuning the thermal SCO characteristics of the complex. The 100% HS state obtained after light irradiation indicates the occurrence of efficient on-surface light-induced spin switching, encouraging the development of light-addressable molecular devices based on SCO complexes

Active Bio-nanocomposites from Litchi Seed Starch, Tamarind Kernel Xyloglucan, and Lignin Nanoparticles to Improve the Shelf-life of Banana (\u3cem\u3eMusa acuminata\u3c/em\u3e)

Valorization of agricultural byproducts to biodegradable packaging films aids in reducing plastic dependency and addressing plastic perils. Herein, starch (LSS) from litchi seeds and xyloglucan (XG) from tamarind kernels were recovered, and composite films were developed. The XG addition strengthened the weak polymer networks of LSS and improved rheological, molecular, morphological, mechanical, and water vapor barrier properties. The incorporation of lignin nanoparticles (LNPs) into the LSS-XG network further increased the tensile strength (14.83 MPa), elastic modulus (0.41 GPa), and reduced surface wettability (80.07°), and water vapor permeability (5.63 ± 0.38 × 10−7 g m−1s−1Pa−1). The phenolic hydroxyls of LNPs imparted strong UV-shielding and free radical scavenging abilities to films. These attributes aided in preserving the quality of coated banana fruits with minimal weight loss and color change. Overall, this research highlights the potential transformation of underutilized abundant byproducts into sustainable active bio-nanocomposites for food packaging and shelf-life extension of fruits

Gold nanomaterials – The golden approach from synthesis to applications

Materials at nanometer scale with special attributes like compact size, large surface ratio, and quantum effect are quite distinct from their bulk counterparts. With the advancement of nanoscience and nanotechnology, innumerable inorganic nanomaterials including semiconductor, metal or metal oxide and carbon, nanomaterials have been designed. The optical, physiochemical, electrical, and biological features of gold nanomaterial make it one of the most widely employed nanomaterials. Gold nanoparticles have a long history in chemistry, going all the way back to the ancient Roman era when they utilized to decorate glasses by staining them. Since the physicochemical properties of gold nanomaterials can be modified by varying their structural dimensions attained by various fabrication processes, gold nanomaterials are suitable contender for colorimetric analysis, biosensor, photothermal transducers and imaging. For decades, scientists have been studying the controlled fabrication of gold nanomaterials as their characteristics and function are extremely reliant on the shape and dimensions of the particle. Gold nanomaterials have shown its potential use in numerous fields like biomedicine and biosensors due to their controllable synthesis steps, lower toxicity, high biocompatibility, adjustable optoelectrical properties, and uncomplicated surface modification. These advantages make gold nanomaterials suitable for a wide range of applications, from the biomedical to the energy and environmental sectors. The application section of this review includes a summarized synopsis of these applications in broader terms. In terms of shape, this paper covers a variety of synthetic methods for producing different gold nanomaterials. The morphologies of gold nanomaterials which includes nanoparticles, nanorods, nanoclusters, nanowire, nanoflower and nanosphere have also been discussed in this paper with the emphasis of recent research projects

Ultrafast laser-induced magneto-optical changes in resonant magnetic x-ray reflectivity

<p>Datasets for the publication "Ultrafast laser-induced magneto-optical changes in resonant magnetic x-ray reflectivity", published in Physical Review B <strong>108</strong>, 054439 (2023).</p><p> </p&gt

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