17 research outputs found
Current induced chiral domain wall motion in CuIr/CoFeB/MgO thin films with strong higher order spin-orbit torques
We investigate the Dzyaloshinskii-Moriya interaction (DMI) and spin-orbit torque effects in cuir/cofeb/mgo heterostructures. to this end, harmonic hall measurements and current induced domain wall motion experiments are performed. the motion of domain walls at zero applied field due to current demonstrates the presence of dmi in this system. we determine the strength of the dmi to be d= 5 /- 3 mu j/m2 and deduce right-handed chirality in domain walls showing a partial neel type spin structure. to ascertain the torques, we perform a second harmonic measurement to quantify the damping- and field-like current induced effective fields as a function of the magnetization direction. from the angular dependent analysis, we identify non-negligible higher order terms for polar magnetization angles theta>0, which need to be included when considering the effective manipulation of spins by current
Coherent X-ray Scattering Reveals Nanoscale Fluctuations in Hydrated Proteins
Hydrated proteins undergo a transition in the deeply supercooled regime,
which is attributed to rapid changes in hydration water and protein structural
dynamics. Here, we investigate the nanoscale stress relaxation in hydrated
lysozyme proteins stimulated and probed by X-ray Photon Correlation
Spectroscopy (XPCS). This approach allows us to access the nanoscale dynamic
response in the deeply supercooled regime (T = 180 K) which is typically not
accessible through equilibrium methods. The relaxation time constants exhibit
Arrhenius temperature dependence upon cooling with a minimum in the
Kohlrausch-Williams-Watts exponent at T = 227 K. The observed minimum is
attributed to an increase in dynamical heterogeneity, which coincides with
enhanced fluctuations observed in the two-time correlation functions and a
maximum in the dynamic susceptibility quantified by the normalised variance
. Our study provides new insights into X-ray stimulated stress
relaxation and the underlying mechanisms behind spatio-temporal fluctuations in
biological granular materials
Impact of the interplay of piezoelectric strain and current-induced heating on the field-like spinâorbit torque in perpendicularly magnetized Ta/Co20Fe60B20/Ta/MgO film
<p>Spinâorbit torques (SOTs) are known to be the most efficient way to manipulate the magnetization direction by electrical currents. While, conventionally, one symmetry component of the SOTs, namely, the damping-like torque, was considered to play a primary role, recently, the significance of the other component, the field-like torque, has been revised, owing to the non-trivial dynamics it can induce in heavy metal/ferromagnet multilayers. In this work, we first discuss the unusual behavior of the field-like SOT in a Ta/CoFeB/Ta/MgO multilayer system with a reduced magnetic anisotropy and demonstrate an energy-efficient approach to manipulate the magnitude of the SOT effective fields. Finally, our results show a possibility to engineer the anisotropy of the field-like SOTs by piezoelectric strain, which can be potentially attractive for application in spintronics.</p>
45° sign switching of effective exchange bias due to competing anisotropies in fully epitaxial Co3FeN/MnN bilayers
Magnetization switching behavior with competing anisotropies in epitaxial Co3FeN/MnN exchange-coupled bilayers
Imaging of current induced NĂ©el vector switching in antiferromagnetic Mn2 Au
The effects of current induced NĂ©el spin-orbit torques on the antiferromagnetic domain structure of epitaxial Mn2Au thin films were investigated by x-ray magnetic linear dichroismâphotoemission electron microscopy. We observed current induced switching of antiferromagnetic domains essentially corresponding to morphological features of the samples. Reversible as well as irreversible NĂ©el vector reorientation was obtained in different parts of the samples and the switching of up to 30% of all domains in the field of view of 10 ÎŒm is demonstrated. Our direct microscopical observations are compared to and fully consistent with anisotropic magnetoresistance effects previously attributed to current induced NĂ©el vector switching in Mn2Au
Electric-Field Control of Spin-Orbit Torques in Perpendicularly Magnetized W / CoFeB / MgO Films
Controlling magnetism by electric fields offers a highly attractive perspective for designing future generations of energy-efficient information technologies. Here, we demonstrate that the magnitude of current-induced spin-orbit torques in thin perpendicularly magnetized CoFeB films can be tuned and even increased by electric-field generated piezoelectric strain. Using theoretical calculations, we uncover that the subtle interplay of spin-orbit coupling, crystal symmetry, and orbital polarization is at the core of the observed strain dependence of spin-orbit torques. Our results open a path to integrating two energy efficient spin manipulation approaches, the electric-field-induced strain and the current-induced magnetization switching, thereby enabling novel device concepts
Nanocrystallites Modulate Intermolecular Interactions in Cryoprotected Protein Solutions
Studying protein interactions at low temperatures has important implications for optimizing cryostorage processes of biological tissue, food, and protein-based drugs. One of the major issues is related to the formation of ice nanocrystals, which can occur even in the presence of cryoprotectants and can lead to protein denaturation. The presence of ice nanocrystals in protein solutions poses several challenges since, contrary to microscopic ice crystals, they can be difficult to resolve and can complicate the interpretation of experimental data. Here, using a combination of small- and wide-angle X-ray scattering (SAXS and WAXS), we investigate the structural evolution of concentrated lysozyme solutions in a cryoprotected glycerolâwater mixture from room temperature (T = 300 K) down to cryogenic temperatures (T = 195 K). Upon cooling, we observe a transition near the melting temperature of the solution (T â 245 K), which manifests both in the temperature dependence of the scattering intensity peak position reflecting proteinâprotein length scales (SAXS) and the interatomic distances within the solvent (WAXS). Upon thermal cycling, a hysteresis is observed in the scattering intensity, which is attributed to the formation of nanocrystallites in the order of 10 nm. The experimental data are well described by the two-Yukawa model, which indicates temperature-dependent changes in the short-range attraction of the proteinâprotein interaction potential. Our results demonstrate that the nanocrystal growth yields effectively stronger proteinâprotein attraction and influences the protein pair distribution function beyond the first coordination shell