Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field

The reversal of the magnetization under the influence of a field pulse has been previously predicted to be an incoherent process with several competing phenomena such as domain wall relaxation, spin wave-mediated instability regions, and vortex-core mediated reversal dynamics. However, there has been no study on the direct observation of the switching process with the aid of a microwave signal input. We report a time-resolved imaging study of magnetization reversal in patterned magnetic structures under the influence of a field pulse with microwave assistance. The microwave frequency is varied to demonstrate the effect of resonant microwave-assisted switching. We observe that the switching process is dominated by spin wave dynamics generated as a result of magnetic instabilities in the structures, and identify the frequencies that are most dominant in magnetization reversal

Sample cartridge with built in miniature molecule evaporator for in situ measurement with a photoemission electron microscope

We present a new sample holder that is compatible with Photoemission Electron Microscopes PEEMs and contains a molecule evaporator. With the integrated low cost evaporator, a local and controlled material deposition in clean ultra high vacuum conditions can be achieved minimizing the contamination of the analysis chamber. Different molecule systems can easily be studied by exchanging the sample holder. This opens up new possibilities for in situ investigation of thin film growth by means of spectromicroscopy and element selective imaging at the nanometer scale. As an example of the performances of the setup, we present a study of the hybrid inorganic organic system HIOS consisting of the organic acceptor molecule 2,2 amp; 8242; perfluoronaphthalene 2,6 diylidene dimalononitrile F6TCNNQ and ZnO, which is of great interest for novel HIOS based optoelectronic devices. Here, the ZnO surface work function modification by F6TCNNQ adsorption is investigated in situ in a spatially resolved manner. In addition, we employ PEEM to selectively probe the chemical state of F6TCNNQ molecules in contact with ZnO in the first monolayer and those molecules located in multilayers in 3D island

Spatially resolved X ray absorption spectroscopy investigation of individual cation intercalated multi layered Ti3C2Tx MXene particles

Ti3C2Tx MXene is a two dimensional 2D material possessing highly active hydrophilic surfaces coupled with high metallic conductivity. Cations intercalation between the Ti3C2Tx nanosheets has a significant role in many applications such as water purification, desalination, and electrochemical energy storage. The pseudocapacitive charging mechanism involving surface redox reactions at the Ti3C2Tx surface enables higher energy densities than electrical double layer capacitors, and higher power densities than batteries. In this context, the oxidation state of surface Ti atoms involved in redox reactions has a high impact on the capacitance of Ti3C2Tx MXene and this can be impacted by cation intercalation. Thus, the electronic structure of multi layered Ti3C2Tx particles is investigated by X ray absorption XA spectroscopy, while also benefitting from a high spatial resolution of 30 nm from X ray photoemission electron microscopy. In this work, the XA spectra from multi layered intercalated Ti3C2Tx particles of different thicknesses were recorded at the Ti L and O K edges. The Ti oxidation state in pristine, Li , and Mg intercalated Ti3C2Tx was found to be thickness dependent, while Na and K intercalated Ti3C2Tx particles did not reveal differences upon changing thickness. This work demonstrates thickness dependent modification of the MXene surface chemistry upon cation intercalation in different individual Ti3C2Tx particle

Enhancement of Ti3C2 MXene Pseudocapacitance after Urea Intercalation Studied by Soft X ray Absorption Spectroscopy

MXenes have shown outstanding properties due to their highly active hydrophilic surfaces coupled with high metallic conductivity. Many applications rely on the intercalation between Ti3C2Tx Tx describes the OH, F and O surface terminations flakes by ions or molecules, which in turn might alter the Ti3C2Tx surface chemistry and electrochemical properties. In this work, we show that the capacitance, rate capability, and charge carrier kinetics in Ti3C2Tx MXene electrodes are remarkably enhanced after urea intercalation u Ti3C2Tx . In particular, the areal capacitance increased to 1100 mF cm2, which is 56 higher than that of pristine Ti3C2Tx electrodes. We attribute this dramatic improvement to changes in the Ti3C2Tx surface chemistry upon urea intercalation. The oxidation state and the oxygen bonding of individual Ti3C2Tx flakes before and after urea intercalation are probed by soft X ray absorption spectroscopy XAS at the Ti L and O K edges with 30 nm spatial resolution in vacuum. After urea intercalation, a higher Ti oxidation state is observed across the entire flake compared to pristine Ti3C2Tx. Additionally, in situ XAS of u Ti3C2Tx aqueous dispersions reveal a higher Ti oxidation similar to dry samples, while for pristine Ti3C2Tx the Ti atoms are significantly reduced in water compared to dry sample

Layer Dependent Magnetic Domains in Atomically Thin Fe5GeTe2

Magnetic domain formation in two dimensional 2D materials gives perspectives into the fundamental origins of 2D magnetism and also motivates the development of advanced spintronics devices. However, the characterization of magnetic domains in atomically thin van der Waals vdW flakes remains challenging. Here, we employ X ray photoemission electron microscopy XPEEM to perform layer resolved imaging of the domain structures in the itinerant vdW ferromagnet Fe5GeTe2 which shows near room temperature bulk ferromagnetism and a weak perpendicular magnetic anisotropy PMA . In the bulk limit, we observe the well known labyrinth type domains. Thinner flakes, on the other hand, are characterized by increasingly fragmented domains. While PMA is a characteristic property of Fe5GeTe2, we observe a spin reorientation transition with the spins canting in plane for flakes thinner than six layers. Notably, a bubble phase emerges in four layer flakes. This thickness dependence, which clearly deviates from the single domain behavior observed in other 2D magnetic materials, demonstrates the exciting prospect of stabilizing complex spin textures in 2D vdW magnets at relatively high temperature

Strain tuning of N el temperature in YCrO3 epitaxial thin films

Epitaxial strain is a useful handle to engineer the physical properties of perovskite oxide materials. Here, we apply it to orthorhombic chromites that are a family of antiferromagnets showing fruitful functionalities as well as strong spin lattice coupling via antisymmetric exchange interaction along Cr O Cr bonds. Using pulsed laser deposition, we grow YCrO3 thin films on various substrates imposing strain levels in the range from amp; 8722;1.8 to 0.3 . The films are stoichiometric with a 3 valence for Cr both within the films and at their surface. They display an antiferromagnetic spin order below their N el temperature, which we show can be strongly tuned by epitaxial strain with a slope of amp; 8722;8.54 K . A dimensionless figure of merit defined as the slope normalized by the N el temperature of bulk is determined to be 6.1, which is larger than that of other perovskites, such as manganites 5.5 , ferrites 2.3 , or nickelates 4.6 . Density functional theory simulations bring insight into the role of Cr O bond lengths and oxygen octahedral rotations on the observed behavior. Our results shed light on orthorhombic chromites that may offer an energy efficient piezo spintronic operatio