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Members of the Shank family of postsynaptic scaffold proteins (Shank1-3) link neurotransmitter receptors to the actin cytoskeleton in dendritic spines through establishing numerous interactions within the postsynaptic density (PSD) of excitatory synapses. Large Shank isoforms carry at their N-termini a highly conserved domain termed the Shank/ProSAP N-terminal (SPN) domain, followed by a set of ankyrin repeats. Both domains are involved in an intramolecular interaction which is believed to regulate accessibility for additional interaction partners, such as Ras family G-proteins, αCaMKII and cytoskeletal proteins. Here we analyse the functional relevance of the SPN-Ank module; we show that binding of active Ras or Rap1a to the SPN domain can differentially regulate the localization of Shank3 in dendrites. In Shank1 and Shank3, the linker between the SPN and Ank domains binds to inactive αCaMKII. Due to this interaction, both Shank1 and Shank3 exert a negative effect on αCaMKII activity at postsynaptic sites in micein vivo. The relevance of the SPN-Ank intramolecular interaction was further analysed in primary cultured neurons; here we observed that in the context of full-length Shank3, a closed conformation of the SPN-Ank tandem is necessary for proper clustering of Shank3 on the head of dendritic spines. Shank3 variants carrying Ank repeats which are not associated with the SPN domain lead to the atypical formation of postsynaptic clusters on dendritic shafts, at the expense of dendritic spines. Our data show that the SPN-Ank tandem motif contributes to the regulation of postsynaptic signalling, and is also necessary for proper targeting of Shank3 to postsynaptic sites. Our data also suggest how missense variants found in autistic patients which alter SPN and Ank domains affect the synaptic function of Shank3.

The formation of healthy tissue involves continuous remodeling of the extracellular matrix (ECM). Whilst it is known that this requires integrin-associated cell-ECM adhesion sites (CMAs) and actomyosin-mediated forces, the underlying mechanisms remain unclear. Here, we examine how tensin3 contributes to the formation of fibrillar adhesions (FBs) and fibronectin fibrillogenesis. Using BioID mass spectrometry and a mitochondrial targeting assay, we establish that tensin3 associates with the mechanosensors such as talin and vinculin. We show that the talin R11 rod domain binds directly to a helical motif within the central intrinsically disordered region (IDR) of tensin3, whilst vinculin binds indirectly to tensin3 via talin. Using CRISPR knock-out cells in combination with defined tensin3 mutations, we show (i) that tensin3 is critical for the formation of α5β1-integrin FBs and for fibronectin fibrillogenesis, and (ii) the talin/tensin3 interaction drives this process, with vinculin acting to potentiate it.

The ability to control and tune magnetic dissipation is a key concept of emergent spintronic technologies. Magnon scattering processes constitute a major dissipation channel in nanomagnets, redefine their response to spin torque, and hold the promise for manipulating magnetic states on the quantum level. Controlling these processes in nanomagnets, while being imperative for spintronic applications, has remained difficult to achieve. Here, we propose an approach for controlling magnon scattering by a switch that generates nonuniform magnetic field at nanoscale. We provide an experimental demonstration in magnetic tunnel junction nanodevices, consisting of a free layer and a synthetic antiferromagnet. By triggering the spin-flop transition in the synthetic antiferromagnet and utilizing its stray field, magnon interaction in the free layer is toggled. The results open up avenues for tuning nonlinearities in magnetic neuromorphic applications and for engineering coherent magnon coupling in hybrid quantum information technologies.

Recent experimental observation of inertial spin dynamics calls upon holistic reevaluation of the theoretical framework of magnetic resonance in ferromagnets. Here, we derive the secular equation of an inertial spin system in analogy to the ubiquitous Smit-Beljers formalism. We find that the frequency of precessional ferromagnetic resonances is decreased as compared to the noninertial case. We also find that the frequency of nutational resonances is generally increased due to the presence of magnetic anisotropy and applied magnetic field. We obtain exact solutions of the secular equation and approximations that employ the terminology of noninertial theory and thus allow for convenient estimates of the inertial effects.

Complex glycans are ubiquitous in Nature and essential to life; glycosaminoglycans surround all mammalian cells and are key players in development and cell signalling, while plant cell walls provide structural rigidity, even during phases of growth, and plant cells account for the vast majority of carbon fixation on earth. Despite their diverse roles, however, only a fraction of the potential chemical space hypothetically available to complex glycans has been explored. New regions of this chemical space can, nevertheless, be accessed by generating new ones which do not occur in Nature or, by modifying naturally-occurring polysaccharide structures. Collectively, we term these new polysaccharides (NPs). Two synthetic routes to NPs are described here; the de novo route, directly from monosaccharide starting materials and the functionalization route, involving glycosylation of existing polysaccharides. The reaction in both cases involves a simple condensation step under microwave heating, catalysed by benign organic acids. The approach is illustrated by the generation of structures with biological activities ranging from cell signalling and inhibition of bacterial growth to mimicking carbohydrate antigens from pathogenic microorganisms. The method is as applicable to fine chemicals as it is to industrial waste, for example, biotechnologically-derived D-allulose (D-psicose) or biofermentation waste, and enables rapid access to extensive chemical space, encompassing both existing biological structures and those previously unattainable. Accessing this chemical space unlocks new functionalities and applications for complex glycans in the biological, medical, biotechnological and materials science arenas.

We develop an approach for toggling magnon processes at nanoscale. We demonstrate an experimental proof-of-concept in magnetic tunnel junction nanodevices, consisting of a free layer and a synthetic antiferromagnet. By triggering the spin-flop transition in the synthetic antiferromagnet and utilizing its nonuniform dipole field, we controllably modify magnon interaction in the free layer. We achieve its tunability by at least one order of magnitude and realize two distinct dissipative states. The results open up an avenue for controlling magnon processes by external stimuli at nanoscale and show prospects for a variety of spin-torque applications, magnetic neural networks, and hybrid quantum information technologies. An immediate consequence of modified magnon interaction is nanomagnet's response to spin-torques. In particular, we show that degenerate resonant three-magnon process inverts an antidamping spin-torque into a torque that enhances dissipation. Supported by NSF-ECCS-1810541.

Long-range spin transport in magnetic systems can be achieved by means of exchange-mediated spin textures with robust topological winding - a phenomenon referred to as spin superfluidity. Its experimental signatures have been discussed in antiferromagnets which are nearly free of dipolar interaction. In ferromagnets, which present with non-negligible dipole fields, however, realization of such spin transport has remained a challenge. Using micromagnetic simulations, we investigate exchange-mediated spin transport in extended thin ferromagnetic films. We uncover a two-fluidstate, in which the long-range spin transport by spin textures co-exists with and is stabilized by spin waves, as well as a soliton-screened spin transport regime at high spin injection biases. Both states are associated with distinct spin texture reconstructions near the spin injection region and sustain spin transport over large distances.

Nanoscale magnets are the building blocks of many existing and emergent spintronic applications, e.g. nonvolatile spin torque memory, spin torque oscillators, neuromorphic and probabilistic computing. Controlling magnetic damping in nanomagnets holds the key to improving the performance of future technologies. Here, we experimentally demonstrate and theoretically corroborate that a ferromagnetic nano-particle (free layer of a magnetic tunnel junction (MTJ) nanopillar) can exhibit spin dynamics qualitatively different from those predicted by the harmonic oscillator model. Nonlinear contributions to the damping can be unusually strong, and the effective damping parameter itself can exhibit resonant dependence on field/frequency [1].

Modern spectroscopic techniques for the investigation of magnetization dynamics in micro and nanostructures or thin films typically use microwave antennas. They are directly fabricated on top of the sample by means of electron-beam lithography (EBL). Following this approach, every magnetic structure on the sample needs its own antenna, resulting in additional EBL steps and layer-deposition processes. Here, we demonstrate an approach for magnetization excitation that is suitable for optical and nonoptical spectroscopy techniques. By patterning the antenna on a separate flexible glass cantilever and insulating it electrically, we solve the mentioned issues. Since we use flexible transparent glass as the antenna substrate, optical spectroscopy techniques like microfocused Brillouin-light-scattering microscopy ($\ensuremath{\mu}\mathrm{BLS}$), time-resolved magneto-optical Kerr-effect measurements, or optically detected magnetic resonance measurements can be carried out at visible laser wavelengths. As the antenna is detached from the sample it can be freely positioned in all three dimensions to address only the desired magnetic structures and to achieve an effective excitation. We demonstrate the functionality of these antennas using $\ensuremath{\mu}\mathrm{BLS}$ and compare coherently and thermally excited magnon spectra to reveal an enhancement of the signal by a factor of about 400 due to the strong excitation by the antenna. Moreover, we succeed in characterizing yttrium-iron-garnet thin films with spatial resolution using optical ferromagnetic resonance experiments. We analyze the spatial excitation profile of the antenna by measuring the magnetization dynamics in two dimensions. The technique is furthermore applied to investigate injection locking of spin Hall nano-oscillators in the most favourable geometry with the highest spin-torque efficiency.

Yttrium iron garnet (YIG) is a material with unique properties that make it very attractive for use in microwave applications, such as frequency-selective limiters and logic processing. However, the decay of a spin wave's amplitude as it propagates in the material curbs the use of YIG in practical applications. To surmount this limitation, in this study the surface spin currents of a topological insulator are used to enhance the spin-wave amplitude in adjacent YIG. In addition, interesting properties of magnons are observed and investigated, to advance spintronics.

Nonlinear magnon scattering redefines how nanomagnets respond to spin currents., Magnetic damping is a key metric for emerging technologies based on magnetic nanoparticles, such as spin torque memory and high-resolution biomagnetic imaging. Despite its importance, understanding of magnetic dissipation in nanoscale ferromagnets remains elusive, and the damping is often treated as a phenomenological constant. Here, we report the discovery of a giant frequency-dependent nonlinear damping that strongly alters the response of a nanoscale ferromagnet to spin torque and microwave magnetic field. This damping mechanism originates from three-magnon scattering that is strongly enhanced by geometric confinement of magnons in the nanomagnet. We show that the giant nonlinear damping can invert the effect of spin torque on a nanomagnet, leading to an unexpected current-induced enhancement of damping by an antidamping torque. Our work advances the understanding of magnetic dynamics in nanoscale ferromagnets and spin torque devices.

Non-collinear spin ground states in metallic antiferromagnets can give rise to anomalous Hall effect, which enables magnetic state readout in antiferromagnetic spintronic devices. Here we report growth of highly textured films of a non-collinear antiferromagnet IrMn3 on MgO(111) substrates by magnetron sputtering. The films consist of epitaxial (111) twin domains rotated by 60 degrees within the film plane. The films exhibit partial L12 ordering that supports the non-collinear T1 spin structure predicted to give rise to anomalous Hall effect. An MgO buffer layer evaporated onto the substrate increases the L12 order parameter from 0.4 to 0.75 but destroys the (111) crystallographic texture.

Two easy-plane ferromagnetic layers, antiferromagnetically coupled through a thin nonmagnetic metal layer, form the magnetic analog of a Josephson junction. A current driven spin chemical potential drives a 2 π precession of the in-plane magnetization of each ferromagnet. The participation of the full magnetic moment in the 2 π precession maximizes the giant magnetoresistance and the ac output power. The frequency can be continuously tuned by a dc bias. An applied ac bias results in a time-averaged magnetoresistance with Shapiro-like steps. The multistate mode-locking behavior exhibited by the Shapiro steps may be exploited for applications such as microwave detectors and neuromorphic computing. They may also serve as an experimental signature of spin superfluidity.

We experimentally study nanowire-shaped spin-Hall nano-oscillators based on nanometer-thick epitaxial films of Yttrium Iron Garnet grown on top of a layer of Pt. We show that, although these films are characterized by significantly larger magnetic damping in comparison with the films grown directly on Gadolinium Gallium Garnet, they allow one to achieve spin current-driven auto-oscillations at comparable current densities, which can be an indication of the better transparency of the interface to the spin current. These observations suggest a route for improvement of the flexibility of insulator-based spintronic devices and their compatibility with semiconductor technology.

Magnetic resonance is a quantum phenomenon and describes a resonant interaction of spins with electromagnetic fields. Its understanding requires advanced knowledge of quantum mechanics and condensed matter physics and thus often remains elusive to students. However, the great impact of this phenomenon on medicine, science, and technology makes magnetic resonance an important subject for general education, and it requires a graspable model for translating the physical concepts without resorting to advanced physics. One of the most common and familiar objects related to magnetism is the compass. Here, we develop an inexpensive tabletop demonstration experiment for magnetic resonance. The compass is placed into the magnetic field of a permanent magnet (strong refrigerator magnet); an alternating field of an electromagnetic coil (solenoid) excites a resonant oscillation of the compass needle. The experiment has been proven to catch the attention of audiences of all ages.

Many spintronics applications consist of ultrathin magnetic and nonmagnetic multilayers and require an in-depth understanding of interfacial magnetism and spin transport. Here, we study permalloy/copper/platinum multilayer systems. We find that magnetic damping, perpendicular anisotropy, and proximity magnetization exhibit correlated oscillations as a function of the copper thickness. We ascribe these observations to an oscillatory interlayer coupling between permalloy and platinum. Such interlayer coupling may have a significant impact on the performance of spintronics applications.

Energy loss due to ohmic heating is a major bottleneck limiting down-scaling and speed of nano-electronic devices, and harvesting ohmic heat for signal processing is a major challenge in modern electronics. Here, we demonstrate that thermal gradients arising from ohmic heating can be utilized for excitation of coherent auto-oscillations of magnetization and for generation of tunable microwave signals. The heat-driven dynamics is observed in Y3Fe5O12/Pt bilayer nanowires where ohmic heating of the Pt layer results in injection of pure spin current into the Y3Fe5O12 layer. This leads to excitation of auto-oscillations of the Y3Fe5O12 magnetization and generation of coherent microwave radiation. Our work paves the way towards spin caloritronic devices for microwave and magnonic applications., Harvesting ohmic heat for signal processing is one of major challenges in modern electronics and spin caloritronics, but not yet well accomplished. Here the authors demonstrate a spin torque oscillator device driven by pure spin current arising from thermal gradient across an Y3Fe5O12/Pt interface.

The Meteor-M N 2 spacecraft with microwave radiometer MTVZA-GY has been launched on July 8, 2014 on sun-synchronous orbit at an altitude of 830 km. MTVZA-GY is a 29 channel microwave imager/sounder for remote sensing of the ocean and land surface parameters as well as for measuring total atmospheric water vapor content, total cloud liquid water content, air temperature and humidity profiles. MTVZA GY operates at frequencies10-190 GHz. The total power radiometer configuration is employed. The antenna system of MTVZA-GY consists of an offset parabolic reflector of dimension 65 cm, illuminated by four feed-horns antenna. Results of vicarious calibration and longtime stability study are discussed. Globe MTVZA-GY data are presented. The examples of joint analysis of MTVZA-GY and other remote and ground-based observations of severe marine weather systems and Antarctica are discussed.

We study perpendicular magnetic anisotropy in thin films of Ta/Co20Fe60B20/MgO by ferromagnetic resonance and find a linear temperature dependence for the first and second order uniaxial terms from 5 to 300 K. Our data suggest the possible hybridization of Fe-O orbitals at the CoFeB/MgO interface for the origin of the first order anisotropy. However, we also find that non-interfacial contributions to the anisotropy are present. An easy-cone anisotropy is found for the entire temperature range in the narrow region of film thicknesses around the spin reorientation transition 1.2–1.35 nm.

Manipulation of magnetization by electric field is a central goal of spintronics because it enables energy-efficient operation of spin-based devices. Spin wave devices are promising candidates for low-power information processing, but a method for energy-efficient excitation of short-wavelength spin waves has been lacking. Here we show that spin waves in nanoscale magnetic tunnel junctions can be generated via parametric resonance induced by electric field. Parametric excitation of magnetization is a versatile method of short-wavelength spin wave generation, and thus, our results pave the way toward energy-efficient nanomagnonic devices.

The quantitative investigation of magnetic nanostructures by means of ferromagnetic resonance is demonstrated for single-crystalline iron nanostructures. It is shown that the single-crystalline nature leads to effects not being present in polycrystalline ones and helps to quantitatively interpret the results. First a method is presented that enables one to fabricate epitaxial Fe nanowires starting from a thin film of Fe grown under ultrahigh vacuum conditions on GaAs (110). The system allows, due to the combination of cubic and twofold magnetic anisotropy, to prepare wires whose easy axis in remanence is oriented perpendicular to the wires axis. This unique feature is only achievable in epitaxial systems. Furthermore, nearly perfect Fe nanocubes with 13.6 nm edge length prepared by wet-chemical methods are studied. While the shell of the particles is composed of either Fe3O4 or gamma-Fe2O3, the core consists of metallic Fe. Oxygen and hydrogen plasma are used to remove the ligand system and the oxide shell. The single-crystalline nature of the cubes enables one to quantitatively determine the magnetic properties of the individual particle by means of ferromagnetic resonance measurements on an ensemble together with a model based on the Landau-Lifshitz equation. The measurements reveal a magneto-crystalline anisotropy of K4 = 4.8. 10(4) J/m3 being equal to bulk value and a saturation magnetization which is reduced to M(5K) = (1.2 +/- 0.12). 10(6) A/m (70% of bulk value). The effective damping parameter alpha = 0.03 is increased by one order of magnitude with respect to bulk Fe, showing that magnetic damping in nanostructures differs from the bulk.

The importance of extrinsic spin relaxation processes such as magnon-magnon scattering for the overall damping in ferromagnetic thin films has been shown for low relaxation rate systems. Due to its anisotropic behavior, it offers an opportunity for controlling and tailoring the spin relaxation. In this paper, a ferromagnetic resonance study of a system with pure Gilbert damping Fe94.5Si5.5/MgO(001) is shown. Fe3Si/MgO(001) systems with native magnon-magnon scattering are discussed. Possibilities for inducing magnon-magnon scattering by volume and surface defects in these systems are presented, offering a method for controlled tailoring of the overall damping in thin films.

NiO-passivated nickel nanoparticles were grown on small platinum seeds, which served as catalysts for the reduction of Ni2+ with hydrazine, in aqueous solutions of the cationic surfactant cetyltrimethylammonium bromide. Control of particle size was achieved through manipulation of the reduction conditions, among which the molar ratio between nickel salt and platinum seeds was found to be dominant. HRTEM, XPS, and XRD show the polycrystaline structure of the particles and the presence of metallic Ni, as well as NiOx and Ni(OH)2. The magnetic properties were studied as a function of size and reveal superparamagnetic response at room temperature for 14 nm diameter nanoparticles and ferromagnetic behavior for the nanoparticles with diameters larger than 24 nm. The ferromagnetic nature of bigger Ni particles was found to induce chain formation, even in the absence of external magnetic fields, which is demonstrated through in situ coating with silica, which results in fossilized nanoparticle chains. Additionall...

International audience; We study thin films and magnetic tunnel junction nanopillars based on Ta/Co20Fe60B20/MgO multilayers by electrical transport and magnetometry measurements. These measurements suggest that an ultrathin magnetic oxide layer forms at the Co20Fe60B20/MgO interface. At approximately 160 K, the oxide undergoes a phase transition from an insulating antiferromagnet at low temperatures to a conductive weak ferromagnet at high temperatures. This interfacial magnetic oxide is expected to have significant impact on the magnetic properties of CoFeB-based multilayers used in spin torque memories. (C) 2015 AIP Publishing LLC.

We demonstrate a technique of broadband spin torque ferromagnetic resonance (ST-FMR) with magnetic field modulation for measurements of spin wave properties in magnetic nanostructures. This technique gives great improvement in sensitivity over the conventional ST-FMR measurements, and application of this technique to nanoscale magnetic tunnel junctions (MTJs) reveals a rich spectrum of standing spin wave eigenmodes. Comparison of the ST-FMR measurements with micromagnetic simulations of the spin wave spectrum allows us to explain the character of low-frequency magnetic excitations in nanoscale MTJs., Also see: http://faculty.sites.uci.edu/krivorotovgroup/

We report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10−3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our work demonstrates efficient spin transport across the Pt/LSMO interface.

In the presence of a periodic scattering potential the spin relaxation in ultrathin ferromagnets is not a monotonous function of the frequency. The spin relaxation rate is found to substantially increase at characteristic frequencies related to the periodicity of the magnon scattering potential (see Fig. 1). This is experimentally confirmed in Ni80Fe20 thin films by artificially introducing different scattering periodicities [1]. The lateral struvturing of the thin film is achieved by Cr+ ion implantation with at an energy of 5 keV and a fluence of 5 × 10E15 ions/cm2 through a 100 nm thick polymethyl methacrylate (PMMA) resist covering the whole sample area. Electron beam lithography was used to fabricate 1 mm long-stripes of width s0 and spacing s1 (i.e., with periodicity l = s0 + s1) within the PMMA resist so that the surface becomes Cr-implanted in a stripewise manner. Frequency dependent Ferromagnetic resonance spectroscopy reveals that the magnetic damping may be increased at specific frequencies by a factor of up to 100%. This work is supported by the DFG, SFB 491, Grants No. FA 314/6-1 and No. FA 314/3-2. [1] I. Barsukov et al., Phys. Rev. B 84, 140410(R) (2011)

Experimental investigations on magnetic anisotropy energies of epitaxial ${\text{Fe}}_{100\ensuremath{-}x}{\text{Si}}_{x}$ thin films on MgO(001) have been extended to low Si concentration. We separated different contributions and found that the strain-induced magnetocrystalline anisotropy term favors an in-plane easy axis for the ${\text{Fe}}_{94.5}{\text{Si}}_{5.5}$ sample, but an out-of-plane easy axis for the ${\text{Fe}}_{75}{\text{Si}}_{25}$ sample. First principles calculations using the highly precise full potential linearized augmented plane wave method indicated that this results from the sign change in magnetoelastic coupling coefficient in the composition range. Analysis in electronic structures provides clear insights for the understanding of magnetic anisotropy in these films.

We present results for ferromagnetic resonance measurements in ultrathin magnetic films. Our aim is to investigate quantitatively the damping of spin motions where different sources of damping are present. We investigate a polycrystalline 10-nm-thick Co film grown on GaAs using microwave frequencies between 4 and 24 GHz and different orientations of the static magnetic field. We discuss the role of Gilbert and two-magnon dampings (activated by defects in the film) within the theoretical framework presented some years ago by Arias and Mills [Phys. Rev. B 60, 7395 (1999)] and its extension to the case in which the magnetization is tipped out of the film plane [P. Landeros, R. E. Arias, and D. L. Mills, Phys. Rev. B 77, 214405 (2008)]. It is found that linewidth vs. field angle data are well reproduced by the theory for several frequencies and we obtain information about fundamental parameters as well as the role of defects in the dynamical response of the prototype Co system.

The magnetic anisotropy of epitaxial Fe films with thicknesses in the range of 22142 monolayers (ML) grown on f4 � 2g reconstructed InAs(0 0 1) was investigated by in situ ferromagnetic resonance. The easy magnetization direction was found to be parallel to the ½1 10 � -direction for Fe films below 4 ML, while it rotates by 45 � toward the ½ 100 � -direction. It is observed that both surface-interface and volume contribution to the perpendicular anisotropy favor an easy axis perpendicular to the film plane. The cubic surface-interface anisotropy is relatively large with easy axes along h1 10 i-directions in contrast to the volume contribution which favors easy axes along the h 110 i-directions. The volume contribution is found to be larger than the Fe bulk cubic anisotropy. A thickness independent uniaxial anisotropy has been found in films with a thickness of 2 up to 142 ML.

The spin and orbital magnetism of $8\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thick ${\mathrm{Fe}}_{2.8}{\mathrm{Si}}_{1.2}$, ${\mathrm{Fe}}_{3}\mathrm{Si}$, and ${\mathrm{Fe}}_{3.2}{\mathrm{Si}}_{0.8}$ films epitaxially grown on MgO(001) was determined experimentally by ferromagnetic resonance and superconducting quantum interference device magnetometry and theoretically by fully relativistic density functional theory calculations. The experimental average spin (orbital) moment of the stoichiometric ${\mathrm{Fe}}_{3}\mathrm{Si}$ $[{\ensuremath{\mu}}_{S(L)}^{\mathrm{av}}=1.38(0.051){\ensuremath{\mu}}_{B}]$ is in reasonable agreement with the theoretical one $[{\ensuremath{\mu}}_{S(L)}^{\mathrm{av}}=1.75(0.029){\ensuremath{\mu}}_{B}]$. Slight increases (reductions) of the Fe content are experimentally found to increase (decrease) the spin and orbital moments as predicted by theory. The results reveal an important step toward tailoring spin and orbital magnetism in the binary Heusler alloys.

Nearly perfect single crystalline Fe core-shell nanocubes with (100) facets and 13.6 nm edge length were prepared by wet-chemical methods. While the core is metallic, the shell is composed of either Fe3O4 or γ-Fe2O3. The cubes were deposited onto GaAs substrates with monolayer coverage as proved by scanning electron microscopy. Oxygen and hydrogen plasmas were used to remove the ligand system and the oxide shell. Both types of samples were investigated by ferromagnetic resonance. While the g-factor (g=2.09) and crystalline anisotropy (K4=4.8×104 J/m3) of the pure iron cubes show up with bulk values, the saturation magnetization is reduced to (M(5K)=(1.2±0.12)×106 A/m) 70% of bulk value and the effective damping parameter (α=0.03) is increased by one order of magnitude with respect to bulk Fe.

The composition dependence of the magnetic as well as structural properties of epitaxial $4--40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ ${\mathrm{Fe}}_{3}\mathrm{Si}$ thin films on MgO(001) have been investigated using ferromagnetic resonance, superconducting quantum interference device magnetometry, and magneto-optical Kerr effect. Magnetic anisotropy energy, $g$ factor, and magnetization were determined for different samples with Si concentrations of 20%, 25%, or 30% at room temperature. Additionally, different annealing procedures were applied. The magnetization was determined to be on the order of ${\ensuremath{\mu}}_{0}M\ensuremath{\approx}1\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. It was found that the films have a dominating cubic anisotropy ${K}_{4}\ensuremath{\approx}3\ifmmode\times\else\texttimes\fi{}{10}^{3}\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕{\mathrm{m}}^{3}$ which depends on the thermal treatment of the film and is about 1 order of magnitude smaller than the one of bulk Fe. A small uniaxial in-plane anisotropy of interfacial nature was detected. The perpendicular uniaxial anisotropy term, which is dominated by an interface contribution, favors a perpendicular easy axis. From frequency-dependent ferromagnetic resonance measurements an isotropic $g$ factor was extracted $g=2.075(5)$ for 8 and $40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ samples and $g=2.080(5)$ for the $4\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ one. Different thermal treatments of the sample showed no influence on the $g$ factor. The magnetic anisotropy fields and $g$ factor decrease linearly as the Si concentration increases within the $D{0}_{3}$ regime.

The magnetic relaxation processes following the dynamical excitation of the spin system of ferromagnets are investigated by ferromagnetic resonance (FMR) between 1 and $70\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ using epitaxial ${\mathrm{Fe}}_{3}\mathrm{Si}$ films as a prototype system. Two relaxation channels, i.e., dissipative, isotropic Gilbert damping $G$ as well as anisotropic two-magnon scattering $\ensuremath{\Gamma}$, are simultaneously identified by frequency and angle dependent FMR and quantitatively analyzed. The scattering rates due to two-magnon scattering at crystallographic defects for spin waves propagating in ⟨100⟩ and ⟨110⟩ directions, $\ensuremath{\gamma}{\ensuremath{\Gamma}}_{⟨100⟩}=0.25(2)\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ and $\ensuremath{\gamma}{\ensuremath{\Gamma}}_{⟨110⟩}=0.04(2)\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$, and the Gilbert damping term $G=0.051(1)\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ are determined. We show that changing the film thickness from $8\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}40\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ and slightly modifying the Fe concentration influence the relaxation channels. Our results, which reveal the contributions of longitudinal and transverse relaxation processes may be of general importance for the understanding of spin-wave dynamics in magnetic structures.

The longest relaxation time and sharpest frequency content in ferromagnetic precession is determined by the intrinsic (Gilbert) relaxation rate $G$. For many years, pure iron (Fe) has had the lowest known value of $G=57\text{ }\text{ }\mathrm{MHz}$ for all pure ferromagnetic metals or binary alloys. We show that an epitaxial iron alloy with vanadium (V) possesses values of $G$ which are significantly reduced to $35\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{MHz}$ at 27% V. The result can be understood as the role of spin-orbit coupling in generating relaxation, reduced through the atomic number $Z$.

Morphinone reductase (MR) catalyzes the NADH-dependent reduction of alpha/beta unsaturated carbonyl compounds in a reaction similar to that catalyzed by Old Yellow Enzyme (OYE1). The two enzymes are related at the sequence and structural levels, but key differences in active site architecture exist which have major implications for the reaction mechanism. We report detailed kinetic and solution NMR data for wild-type MR and two mutant forms in which residues His-186 and Asn-189 have been exchanged for alanine residues. We show that both residues are involved in the binding of the reducing nicotinamide coenzyme NADH and also the binding of the oxidizing substrates 2-cyclohexen-1-one and 1-nitrocyclohexene. Reduction of 2-cyclohexen-1-one by FMNH(2) is concerted with proton transfer from an unknown proton donor in the active site. NMR spectroscopy and flavin reoxidation studies with 2-cyclohexen-1-one are consistent with His-186 being unprotonated in oxidized, reduced, and ligand-bound MR, suggesting that His-186 is not the key proton donor required for the reduction of 2-cyclohexen-1-one. Hydride transfer is decoupled from proton transfer with 1-nitrocyclohexene as oxidizing substrate, and unlike with OYE1 the intermediate nitronate species produced after hydride transfer from FMNH(2) is not converted to 1-nitrocyclohexane. The work highlights key mechanistic differences in the reactions catalyzed by MR and OYE1 and emphasizes the need for caution in inferring mechanistic similarities in structurally related proteins.

The structure of pentaerythritol tetranitrate (PETN) reductase in complex with the nitroaromatic substrate picric acid determined previously at 1.55 A resolution indicated additional electron density between the indole ring of residue Trp-102 and the nitro group at C-6 of picrate. The data suggested the presence of an unusual bond between substrate and the tryptophan side chain. Herein, we have extended the resolution of the PETN reductase-picric acid complex to 0.9 A. This high-resolution analysis indicates that the active site is partially occupied with picric acid and that the anomalous density seen in the original study is attributed to the population of multiple conformational states of Trp-102 and not a formal covalent bond between the indole ring of Trp-102 and picric acid. The significance of any interaction between Trp-102 and nitroaromatic substrates was probed further in solution and crystal complexes with wild-type and mutant (W102Y and W102F) enzymes. Unlike with wild-type enzyme, in the crystalline form picric acid was bound at full occupancy in the mutant enzymes, and there was no evidence for multiple conformations of active site residues. Solution studies indicate tighter binding of picric acid in the active sites of the W102Y and W102F enzymes. Mutation of Trp-102 does not impair significantly enzyme reduction by NADPH, but the kinetics of decay of the hydride-Meisenheimer complex are accelerated in the mutant enzymes. The data reveal that decay of the hydride-Meisenheimer complex is enzyme catalyzed and that the final distribution of reaction products for the mutant enzymes is substantially different from wild-type enzyme. Implications for the mechanism of high explosive degradation by PETN reductase are discussed.

We report ferromagnetic resonance measurements of perpendicular magnetic anisotropy in thin films of Ta/Co20Fe60B20/MgO as a function of the Co20Fe60B20 layer thickness. The first and second order anisotropy terms show unexpectedly strong dependence on the external magnetic field applied to the system during the measurements. We propose strong interfacial spin pinning as a possible origin of the field-dependent anisotropy. Our results imply that high-field anisotropy measurements cannot be directly used for quantitative evaluation of zero-field performance parameters of CoFeB-based devices such as spin torque memory.