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Spintronics has been evolving rapidly; it becomes next-generation electronics exploiting both spin and charge degrees of freedom and a primary research field directly linked to topology and nano-magnetism in solid-state physics. In this article, we put our focus on the domain structure and domain wall dynamics based on a cluster magnetic octupole in topological antiferromagnets. Many issues are still not clear in terms of magnetic octupole domains (MODs) and domain walls. We first discuss the current status of the study on the antiferromagnetic domains and walls and then the MODs and walls from detection and manipulation viewpoints. [ABSTRACT FROM AUTHOR]

Presents information on a study that investigated the magnetostatic effect of a ferromagnetic particle array on an underlying two-dimensional superconducting niobium thin film. Methodology of the study; Results and discussion on the study.

We have monitored a magnetization process in a ferromagnetic disk by measuring a bend resistance of semiconductor two-dimensional electron gas (2DEG) lying beneath the disk. Annihilation and nucleation of a vortex in the ferromagnetic disk are clearly seen in the trace of the bend resistance as a function of in-plane magnetic field. The large change in the signal is well reproduced by a simulation based on a semiclassical billiard model. [ABSTRACT FROM AUTHOR]

Presents a study which measured magnetocrystalline anisotropy in neodymium-iron-boron magnet. Experimental details; Results; Discussion.

Evaluates the magnetic image in superconducting magnet (SCM). Purpose of the measurement of the magnetic flux distribution in a small SCM; Image effect; Method used in obtaining the magnetic flux distribution in a superconductive tube.

Deals with a study which investigated the magnetic and structural properties of nickel fine particles coated with palladium in hydrogen atmosphere by means of in situ magnetometry and in situ x-ray diffractometry. Methods; Results; Discussion.

Focuses on a study which investigated the magnetostatic effect of the micron-size ferromagnetic particle array on a two-dimensional superconductor. Details of experimental set-up; Comparison of bare niobium (Nb) film with that of Nb film with ferromagnetic particles; Cause of the difference in the magnetization curves.

Presents a study that explored the idea of metal bonding as a way of achieving anisotropic dense Sm[sub2]Fe[sub17]N[sub3-8] magnets. Intrinsic magnetic properties relevant for permanent magnets; Way of producing nitrides; Use of mechanical alloying.

Presents a study which examined anomalous demagnetization process at very low temperature in neodymium-iron-boron magnets. Observation of heat pulses associated with the Barkhausen magnetization jumps in neodymium-iron-boron magnets; Experimental results; Discussion and conclusions.

Presents a study which examined the concept of magnetic field-induced crystallite alignment in melt-spun praseodymium[sub2]cobalt[sub14]boron system. Determination of crystallization temperatures of the system; Experimental procedure; Results and discussion.

Presents a study that investigated the coercivity and microstructure of melt-spun samarium (iron[sub11] thallium). Experimental methods; Results and discussion.

A novel platform for spin manipulation utilizing the orbital angular momentum (OAM) is preparing the next innovation of spintronics. Analogous to the generation of the spins by the inverse spin Galvanic effect, we could construct a nonzero OAM at surfaces and interfaces with the structural inversion asymmetry or in centrosymmetric bulks. However, all these generation mechanisms are irrelevant to the spin–orbit coupling (SOC) strength, presenting the distinction from the spin generation mechanisms. The nonzero OAM could be utilized for highly efficient spin manipulation, supported by several recent experimental reports. These reports indicate that light metal elements are also useful for OAM-induced spin manipulation. Also, the collaborative spin manipulation by the OAM and the spin angular momentum (SAM) opens an alternative mechanism. Here we review experimental and theoretical new findings on the OAM-induced or OAM–assisted spin manipulation. All these new findings indicate that the OAM-induced spin manipulation opens the door to novel spintronics in terms of mechanism and materials. [ABSTRACT FROM AUTHOR]

Abstract: The transport properties of diffusive spin currents have been investigated in lateral ferromagnetic/nonmagnetic metal hybrid structures. The spin diffusion processes were found strongly dependent on the magnitude of the spin resistances of connected materials. The efficient spin injection and detection are accomplished by optimizing the junction structures on the basis of the spin resistance circuitry. The magnetization switching of a nano-scale ferromagnetic particle and also room temperature spin Hall effect measurements were demonstrated by using an efficient pure-spin-current injection. [ABSTRACT FROM AUTHOR]

Focuses on submicron cobalt (Co) wires which were prepared to investigate the magnetoresistance effect in association with the domain wall formation. Information on ferromagnetic Co wires; Discussion on Co paired disks.

Focuses on arrays of submicron cobalt (Co) rectangular dots with the different aspect ratio and those of Co rectangular antidots which were prepared by a high resolution lithography technique. Magnetic properties of submicron ferromagnetic dots and antidots; Fabrication of arrays of Co rectangular particles; Information on the atomic and magnetic force microscope images for arrays of both dots and antidots.

Examines the exchange coupling mechanism of Cr[sub 70]Al[sub 30]/Fe[sub 19]Ni[sub 81] bilayer films. Consideration of the crystallographic orientation, interface roughness and grain size; Effect of grain size decrease on the H[sub ex] value; Exhibition of a shift in the magnetic hysteresis loop.

Despite significant technological advances in miniaturization and operational speed, modern electronic devices suffer from unescapably increasing rates of Joule heating and power consumption. Avoiding these limitations sparked the quest to identify alternative, charge-neutral information carriers. Thus, spin waves, the collective precessional motion of spins in permanent magnets, were proposed as a promising alternative system for encoding information. In order to surpass the speed, efficiency, functionality and integration density of current electronic devices, magnonic devices should be driven by electric-field induced methods. This review highlights recent progress in the development of electric-field-controlled magnonic devices, including present challenges, future perspectives and the scope for further improvement. Magnonics involves the manipulation of spin waves in order to develop more energy efficient spintronics devices which do not rely on the movement of electronic charge. Here, the authors review the various methods designed to control magnonics with particular focus on voltage i.e. electric-field. [ABSTRACT FROM AUTHOR]

Presents an abstract of the study 'Time Evolution of Magnetization in the FeRh System Near Antiferromagnetic-ferromagnetic Transition Temperature,' by Shinji Yuasa et al., published in the 'Journal of Applied Physics.'

Examines the magnetic properties of nickel-palladium composite fine particles in terms of the magnetic proximity effect and the effect of hydrogenation. Average diameter of the nickel core; Curie temperatures of all the samples; Ferromagnetic behavior observed on isofield magnetization.

We report on the optical characterization of non-magnetic metal (NM)/ferromagnetic (Co20Fe60B20)/MgO heterostructures and interfaces by using mid infrared (MIR) spectroscopic ellipsometry at room temperature. We extracted for the MIR range the dielectric function (DF) of Co20Fe60B20, that is lacking in literature, from a multisample analysis. From the optical modeling of the heterostructures we detected and determined the dielectric tensor properties of a two-dimensional electron gas (2DEG) forming at the NM and the CoFeB interface. These properties comprise independent Drude parameters for the in-plane and out-of plane tensor components, with the latter having an epsilon-near-zero frequency within our working spectral range. A feature assigned to spin–orbit coupling (SOC) is identified. Furthermore, it is found that both, the interfacial properties, 2DEG Drude parameters and SOC strength, and the apparent DF of the MgO layer depend on the type of the underlying NM, namely, Pt, W, or Cu. The results reported here should be useful in tailoring novel phenomena in such types of heterostructures by assessing their optical response noninvasively, complementing existing characterization tools such as angle-resolved photoemission spectroscopy, and those related to electron/spin transport. [ABSTRACT FROM AUTHOR]

Reports on the measurement of the magnetization of Y-Ba-Cu-O superconductors with nonmagnetic or magnetic diffused impurities as a function of the applied field direction. Preparation of the samples; Instruments used to determine the impurity concentration in each sample; Data in the magnetic field dependence of the magnetization hysteresis for the iron-diffused sample.

The magnetic Weyl semimetallic state can lead to intriguing magnetotransport, such as chiral anomaly and the layered quantum Hall effect. Mn3X (X = Sn, Ge) is a noncollinear antiferromagnetic semimetal where a Weyl semimetallic state is stabilized by time-reversal symmetry breaking. Compared to the well-studied Mn3Sn, the Weyl fermion-induced magnetotransport in Mn3Ge has been merely studied. Here, we report an in-depth study on the magnetotransport in a microfabricated Mn3Ge single crystal from room temperature to 10 K. We reveal an anomalous anisotropic magnetoresistance with fourfold symmetry and a positive high-field longitudinal magnetoresistance below the critical temperature (160–170 K). The possible origin is the temperature-induced tilting of the Weyl nodes. Our study helps to understand the magnetotransport properties in the Weyl fermion system. [ABSTRACT FROM AUTHOR]

We report a magnetic imaging method using atomic force microscopy to measure a locally induced anomalous Nernst effect. A tip contact creates a local temperature gradient on a sample surface controlled by a neighboring Joule heating wire. We demonstrate imaging of magnetic domains in a nanowire of the ferromagnetic Weyl semimetal Co2MnGa with a spatial resolution of a sub-hundred nanometer at room temperature. [ABSTRACT FROM AUTHOR]

We review our recent achievements on optimization of spin injection from ferromagnetic into non-magnetic metals and characterization of spin transport properties in the non-magnetic nano-structures. We have realized the efficient spin injection by solving spin resistance mismatch problem in spin diffusion process across the interface between ferromagnetic and nonmagnetic metals. We analyzed temperature dependent spin relaxation length and time in Ag within the framework of the Elliot–Yafet mechanism based on spin–orbit interaction and momentum relaxation. The spin relaxation length in a light metal Mg is found comparable to that of Ag due to its peculiar electronic band structure in which so called spin-hotspots dramatically enhance spin relaxation. Spin relaxation properties in various metals are also quantitatively discussed. We employed commonly used Hanle effect measurements to characterize spin relaxation of spin current and reexamined both theoretically and experimentally the effect of spin absorption at the interface. The affected spatial profile of chemical potential due to the longitudinal and transverse spin absorption results in the broadened Hanle curve. All the Hanle curves both in metallic and semi-conductive materials including graphene fall into the universal scaling plot. Anatomy of spin injection properties of the junction and spin transport properties in non-magnetic metal is shown in tables. [ABSTRACT FROM AUTHOR]

We propose an optical-acoustic means to excite broadband terahertz antiferromagnetic (AFM) spin wave in a metal/insulator/antiferromagnet heterostructure. The AFM spin wave is excited by an ultrafast strain wave triggered by a femtosecond pulsed laser based on photoacoustic conversion. This spin wave comprises an AFM exchange spin wave and a magnetoelastic spin wave. Their dispersion curves are overlapped in a wide frequency range by manipulating the Dzyaloshinskiiâ€"Moriya interaction, which is accompanied by lifting the degeneration of the spin-wave modes with opposite chirality. This optical-acoustic excitation of spin waves exploits the laser-induced ultrafast strain waves and avoids the thermal effect from the laser. It paves a way to develop novel AFM devices that can apply for ultrafast information processing and communication. [ABSTRACT FROM AUTHOR]

We report the magnetic vortex dynamics of 1-D chains of nanomagnetic disks under a time-dependent magnetic field localized at one end of the chain. The transmission of the peak amplitude of the gyrotropic excitation mode of the vortex core along the chain has been actively controlled by manipulating the geometry and condition of preparation of the magnetic ground states of the chains. The transmission is maximum for direct magnetostatic coupling and identical chirality of the nanodisks with geometric asymmetry. Dynamics of the optimized system under a global excitation field has also been investigated to understand the role of magnetostatic interaction in the energy transfer under the local excitation field. The observations are particularly important for the design of fast spin logic systems and the magnonic crystals. [ABSTRACT FROM AUTHOR]

A number of proposed next-generation electronic devices, including novel memory elements and versatile transistor circuits, rely on spin currents, that is, the flow of electron angular momentum. A spin current may interact with a magnetic nanostructure and give rise to spin-dependent transport phenomena, or excite magnetization dynamics. In contrast to a spin-polarized charge current, a pure spin current does not produce any charge-related spurious effects. One way to produce a pure spin current is non-local electrical-spin injection, but this approach has suffered so far from low injection efficiency. Here, we demonstrate a significant enhancement of the non-local injection efficiency in a lateral spin valve prepared with an entirely in situ fabrication process. Improvements to the interface quality and the device structure lead to an increase of the spin-signal amplitude by an order of magnitude. The generated pure spin current enables the magnetization reversal of a nanomagnet with the same efficiency as in the case of using charge currents. These results are important for further theoretical developments in multi-terminal structures, but also with a view towards realizing novel devices driven by pure spin currents. [ABSTRACT FROM AUTHOR]

Spinconversion is a collective concept underlying spin mediated energy interconversion among electricity, light, sound, vibration, and heat. Particularly in the last couple of decades, the increasing research efforts result in enhancements of spinconversion efficiencies and the discovery of novel spinconversion mechanisms. Here, an overview of the progress in spinconversion is layed out. In particular, the involvement of band crossings at which quasiparticles are formed with consequences beyond that of efficient spinconverison are discussed. [ABSTRACT FROM AUTHOR]

Spin–orbit torque induced ferromagnetic magnetization switching brought by injecting a charge current into strong spin–orbit-coupling materials is an energy-efficient writing method in emerging magnetic memories and spin logic devices. However, because of the short spin coherence length in ferromagnetic layers, the interfacial effective spin–orbit torque typically leads to high critical current density for switching thick ferromagnet, which goes against low-power and high-density requirements. Here, we experimentally demonstrate efficient bulk spin–orbit torque-driven perpendicular magnetization switching under relatively low critical current density in thick Pt/Co multilayers with gradient-induced symmetry breaking. Through tuning the thickness gradient of Pt, the spin–orbit torque efficiency and switching chirality can be highly controlled, which also indicates that net spin current arises from gradient. Meanwhile, x-ray absorption spectroscopy results reveal that the atomic intermixing can significantly enhance the spin–orbit torque efficiency through improving the strength of spin–orbit-coupling of Pt. We also establish a micromagnetic model by taking both gradient-induced and intermixing-enhanced spin–orbit torque into account to well describe the experimental observations. This work would blaze a promising avenue to develop novel spin–orbit torque devices for high-performance spintronic memory and computation systems. [ABSTRACT FROM AUTHOR]

We report here an experimental observation of dynamic dipolar coupling induced magnon–magnon coupling and spin wave (SW) mode splitting in Ni80Fe20 cross-shaped nanoring array. Remarkably, we observe an anticrossing feature with minimum frequency gap of 0.96 GHz and the corresponding high cooperativity value of 2.25. Interestingly, splitting of the highest frequency SW mode occurs due to the anisotropic dipolar interactions between the cross nanorings. Furthermore, using micromagnetic simulations we demonstrate that the coupled SW modes propagate longer as opposed to other modes present in this system. Our work paves the way towards integrated hybrid systems-based quantum magnonics and on-chip coherent information transfer. [ABSTRACT FROM AUTHOR]

The T-shaped spin conversion device consisting of ferromagnetic and spin Hall (or spin conversion) materials is an indispensable component in a new type of logic circuit called a magnetoelectric spin–orbit device. We examine the influence of the planar Hall effect (PHE) on the output signal in the T-shaped device. Angular dependences of decomposed even and odd components in the signal reveal that the PHE causes an even-symmetric component in the output signal because the magnetic moment continuously rotates clockwise (or counterclockwise). Thus, the PHE makes it challenging to detect odd magnetic field responses induced by the inverse spin Hall effect containing the zero-field magnetic state information. We can suppress the adverse effect by choosing a low anisotropic magnetoresistance ferromagnet. This study gives valuable information for designing the optimal T-shaped structure for the magnetoelectric logic device application. [ABSTRACT FROM AUTHOR]

Developing a technology to electrically manipulate a Weyl semimetal state is a vital step for designing a nonvolatile memory using topologically robust properties. Recently, such manipulation is realized for the first time in the antiferromagnetic Weyl semimetal Mn3Sn using the readout signal of anomalous Hall effect in the Mn3Sn/heavy metal (Pt, W) heterostructures. Here, it is reported that the switching of Hall signal can be significantly enhanced by 1) removing the buffer layer of Ru to adjust the crystal orientation of Mn3Sn, and 2) annealing after deposition of the heavy metal to change the interfacial condition. The switching of the Hall resistance is 0.35 Ω in the Mn3Sn/W sample, which becomes one order of magnitude larger than the previously reported value using Ru/Mn3Sn/Pt heterostructures. Moreover, by increasing the read current, it is found that the readout voltage may go well beyond 1 mV, a milestone for future applications in memory technology. [ABSTRACT FROM AUTHOR]

A magnetic Weyl semimetal is a recent focus of extensive research as it may exhibit large and robust transport phenomena associated with topologically protected Weyl points in momentum space. Since a magnetic texture provides a handle for the configuration of the Weyl points and its transport response, understanding of magnetic dynamics forms the basis for future control of a topological magnet. Mn3Sn is an example of an antiferromagnetic Weyl semimetal that exhibits a large response comparable to the one observed in ferromagnets despite a vanishingly small magnetization. The noncollinear spin order in Mn3Sn can be viewed as a ferroic order of cluster magnetic octupole and breaks the time‐reversal symmetry, stabilizing Weyl points and the significantly enhanced Berry curvature near the Fermi energy. Herein, the first observation of time‐resolved octupole oscillation in Mn3Sn is reported. In particular, the giant effective damping of the octupole dynamics is found, and it is feasible to conduct an ultrafast switching at <10 ps, a hundred times faster than the case of spin‐magnetization in a ferromagnet. Moreover, high domain wall velocity over 10 km s−1 is theoretically predicted. This work paves the path toward realizing ultrafast electronic devices using the topological antiferromagnet. [ABSTRACT FROM AUTHOR]

Control of magnetization direction is essential for the wide application of ferromagnets; it defines the signal size of memory and sensor. However, the magnetization itself causes a dilemma. While its size matters to obtain strong responses upon its reversal, the large magnetization concomitantly suppresses the range of its directional control because of the demagnetizing field. On the other hand, realization of the desired magnetic anisotropy requires careful engineering of crystalline and interfacial effects to overcome the demagnetization barrier. Thus, it would be ideal if one could find alternative magnets that carry no magnetization but strong responses. The discovery of a topological metallic state in the antiferromagnet Mn3Sn is significant; they host a large Berry curvature in momentum space, enabling the observation of disproportionately large transverse responses such as anomalous Hall and Nernst effects, the key functionalities for replacing ferromagnets in the magnetic devices. Here, the experimental realization of omnidirectional control of the large responses in an antiferromagnet is reported. In particular, it is demonstrated that the absence of shape anisotropy enables the omnidirectional control, and lifts the shape constraint in designing the magnetic devices. This work lays the technological foundation for developing simple‐structured high‐performance devices including multi‐level memory and heat flux sensor. [ABSTRACT FROM AUTHOR]

The spin-orbit torque (SOT) using spin Hall effect has led to significant innovations in spintronics. Recently, SOT switching of an antiferromagnetic state of the Weyl semimetal Mn3Sn is realized by passing electrical current into Mn3Sn/heavy metal heterostructures. Here we demonstrate the SOT switching of Hall resistance in polycrystalline Mn3Sn/Pt, Mn3Sn/W and Mn3Sn/Cu/Pt, Mn3Sn/Cu/W heterostructures. Our experiments indicate that the sign of the spin Hall angle of heavy metals determines the direction of magnetic switching in both devices with and without Cu insertion layer, being consistent with the SOT mechanism. In Mn3Sn/Pt and Mn3Sn/W bilayer devices, the critical current density of electrical switching is ∼1011A/m2 in heavy metals. In addition, we find that the volume fraction of the switched Mn3Sn domain is nearly the same in devices with and without Cu layer, which indicates that the spin current generated from the spin Hall effect of Pt or W contributes dominantly to the SOT compared to possible interfacial effects at Mn3Sn/heavy metal interface. [ABSTRACT FROM AUTHOR]

Coupled gyration modes of the magnetic vortices are studied in two separated disks. We have experimentally detected that all four modes are selectively excited mainly by the spin-transfer torque, depending on the combination of their polarities and chiralities. The evaluated dipolar coupling intensity shows a certain decrease from the rigid vortex model. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated dynamics of paired domain walls in a microfabricated ferromagnetic ring by using a ballistic transport character of a two-dimensional electron gas (2DEG) microcross. The stray field from the domain walls results in a change in the bend resistance of the 2DEG cross lying beneath the ferromagnetic ring depending on the positions of the domain walls. The measurements for different directional angles of the applied magnetic field reveal that the domain wall behavior is strongly affected by identical local defects in the ring. We have also studied a response of paired domain walls under a pulsed magnetic field. We find that the paired domain walls switch the positions without annihilation under a pulsed magnetic field with a short rise time. [Copyright &y& Elsevier]

The authors have investigated dynamics of paired domain walls in a ferromagnetic ring circuit, driven by a variable pulsed magnetic field. The magnetic reversal accompanied by the propagations of the domain walls depends not only on the amplitude but also on the rise time of the applied pulsed magnetic field. The threshold of the rise time is found comparable to the propagation time of a domain wall along a half-path of the ring. This finding may be useful for the high speed operation of the magnetic logic devices based on the domain wall motion. [ABSTRACT FROM AUTHOR]

We have studied the magnetic and transport properties of Co2MnGa (CMG) thin films grown on MgO(100) substrates in terms of their chemical evolution from amorphous to ordered L21 phases at the substrate temperature Ts during the thin film deposition. Interestingly, the chemical order and magnetic properties sharply change depending on Ts. The CMG film deposited at Ts = 550 °C exhibits the L21-ordered structure and the magnetization of 3.5 μB/f.u., while the CMG film deposited at Ts = 300 °C shows a B2-ordered structure and a relatively lower magnetization of 3 μB/f.u., possibly due to the Mn–Mn antiferromagnetic interactions. A metallic behavior of the electrical resistivity appeared in the CMG film deposited at Ts = 550 °C, whereas the semiconducting behavior appeared in the CMG films deposited at 300 °C and room temperature. Moreover, we found that the absolute value of α = d(Δρ)/d(T1/2) in the low-temperature range below about 20 K is a measure to evaluate the degree of the chemical disorder. In a Hall effect measurement, the L21-ordered CMG film obtained at Ts = 550 °C shows a sizable anomalous Hall resistivity of 15 µΩ cm. This study unveils the relation between Ts and atomic ordering, providing a new pathway for optimizing the chemical order. [ABSTRACT FROM AUTHOR]

Surface acoustic waves (SAWs) in the GHz frequency range can inject spin currents dynamically into adjacent non-magnetic layers via the spin pumping effect associated with ferromagnetic resonance. Here, we demonstrate an enhancement of acoustic ferromagnetic resonance and spin current generation by a pair of SAW reflector gratings, which form an acoustic analog of the distributed Bragg reflector cavity. In the experiment, we confirmed 2.04 ± 0.02 times larger SAW power absorption in a device with cavity than in the case of no acoustic cavity. We confirmed up to 2.96 ± 0.02 times larger spin current generation by measuring electric voltages generated by the inverse Edelstein effect at the interface between Cu and Bi2O3. The results suggest that acoustic cavities would be useful to enhance the conversion efficiency in SAW driven coupled magnon–phonon dynamics. [ABSTRACT FROM AUTHOR]

Antiferromagnets exhibiting distinctive responses to the electric and magnetic fields have attracted attention as breakthrough materials in spintronics. The current-induced Néel-order spin-orbit torque can manipulate the antiferromagnetic domain wall (AFDW) in a collinear CuMnAs owing to a lack of local inversion symmetry. Here, we demonstrate that the electrical nucleation, displacement, and detection of AFDWs are also possible in a noncollinear antiferromagnet, i.e., chiral Mn3Sn with local inversion symmetry. The asymmetric magnetoresistance measurements reveal that AFDWs align parallel to the kagome planes in the microfabricated wire. Numerical calculation shows these AFDWs consist of stepwise sub-micron size Bloch wall-like spin textures in which the octupole moment gradually rotates over three segments of domain walls. We further observed that the application of a pulse-current drives these octupole based AFDWs along the wire. Our findings could provide a guiding principle for engineering the AFDW structure in the chiral antiferromagnetic materials. Antiferromagnetic systems for application in spintronics are less developed that their ferromagnetic counterparts but offer the prospect of increased stability and speed in their magnetisation dynamics. Here, the authors investigate the electrical detection and displacement of antiferromagnetic domain walls in Mn3Sn single crystals. [ABSTRACT FROM AUTHOR]

Non-collinear antiferromagnet Mn3Sn is a functional material that exhibits the magneto-optical Kerr effect (MOKE) as well as the anomalous Hall effect, arising from the nonvanishing Berry curvature in the broken time-reversal symmetry lattice system likewise the ferromagnets. Mn3Ge, isostructural to Mn3Sn, is also expected to exhibit a similar MOKE but has not been demonstrated yet. In this study, we performed the MOKE measurement in a Mn3Ge single crystal and obtained a large polar MOKE signal (∼8.2 mdeg) and a longitudinal MOKE signal (∼5.6 mdeg). Furthermore, by applying hyperfine polishing and annealing to the surface, we rebuilt a homogenous surface and largely improved the reproducibility of the MOKE signal in Mn3Ge. [ABSTRACT FROM AUTHOR]

We investigate the transverse response under the out-of-plane magnetic field for magnetic heterostructures with Cu/Bi2O3 or Ag/Bi2O3 Rashba interfaces. We detect opposite contributions on the transverse resistance by the Cu/Bi2O3 and Ag/Bi2O3 interfaces, which interestingly coincide well with the opposite signs of the spin/charge interconversion from the two interfaces. We suppose the opposite influences on the transverse resistance feature spin swapping occurrence of the converted spin current. The transverse spin flow emerges due to the spin swapping in both Cu and Ag layers, but the direction of the spin flow is opposed depending on the spin direction of the converted spin current. [ABSTRACT FROM AUTHOR]

We investigate the effect of sample size on the anomalous Nernst effect (ANE) in a device formed from chiral antiferromagnetic Mn3Sn. We also investigate its magnetic domains by employing focused ion beam lithography. Mn3Sn is a suitable material for studying the thermoelectric effect in the presence of antiferromagnetic domains because it exhibits a large ANE. In the Mn3Sn device used in this study, a Ta layer acts as a heater; the heat produced via Joule heating diffuses through a sapphire substrate into the thin flake of Mn3Sn. The Nernst signal exhibits a stepwise hysteresis when the sample is subjected to a temperature gradient and magnetic field at 290 K. The stepwise hysteresis depends on the sample shape and size—which affect nucleation, pinning, and depinning processes—but the temperature difference also has a significant effect on the switching process. The domain ratios calculated using the ANE results indicate that the domain size is smaller than 20 μm2. This obtained domain size is in good agreement with the reported experimental values of 10–100 μm2 for the magneto-optical Kerr effect in bulk single-crystal Mn3Sn. Thus, the ANE is a powerful means of obtaining information about the magnetic domains in samples under a temperature gradient, thereby promising a reliable approach to study magnetic domains and spintronics using antiferromagnets. [ABSTRACT FROM AUTHOR]

The ferromagnetic resonance (FMR) driven by surface acoustic wave (SAW) has advantages in magnetic sensors due to its high sensitivity and wireless characteristics. However, the magnetic field remains limited to a small range due to the narrow field range for FMR at a fixed resonance frequency. This paper demonstrates that introducing of a small uniaxial anisotropy field (3 mT) in a Ni film can produce a wide dynamic range with high sensitivity along different magnetic field directions. This effectively widens the field range without sacrificing sensitivity, paving the path for developing the SAW magnetic sensor with both a high sensitivity and wide dynamic range. • SAW driven FMR is limited in a small magnetic field range. • The uniaxial anisotropy modifies the resonant magnetic field of FMR. • The uniaxial anisotropy widens the field range without sacrificing sensitivity. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry (SE) in the visible/near-UV spectral range is applied to monitor optical critical dimensions of quartz, Si, and Ta gratings, namely, the depth, linewidth, and period. To analyze the SE measurements, the rigorous coupled-wave theory is applied, whose implementation is described in detail, referred to as the Airy-like internal reflection series with the Fourier factorization rules taken into account. It is demonstrated that the Airy-like series implementation of the coupled-wave theory with the factorization rules provides fast convergence of both the simulated SE parameters and the extracted dimensions. The convergence properties are analyzed with respect to the maximum Fourier harmonics retained inside the periodic media and also with respect to the fineness of slicing imperfect Ta wires with paraboloidally curved edges. [ABSTRACT FROM AUTHOR]

• Efficient modulation of the spin waves with magnetic field and lattice periodicity in unconventional 2D defective honeycomb lattice. • Observation of configurational anisotropy with six- and two-fold rotational symmetry. • Underpinning the role of lattice arrangement and spacing on the spin wave spectra. • Investigation of the influence of internal magnetic field on the spin wave dynamics for such lattice symmetry. Efficacious control of spin wave dynamics is demonstrated in two-dimensional magnonic crystals in the form of defective honeycomb antidot lattices. The spin wave dynamics of this system is investigated using broadband ferromagnetic resonance spectrometer. A stark modification in magnonic spectra is achieved with the modulation in the lattice spacing and with the bias magnetic field strength and its orientation. A rich band of spin wave modes are obtained for the lattice with smallest periodicity, which finally converges to two modes in case of the largest one. The spin wave modes in all lattices possess a strong anisotropic behaviour with a six- and two-fold rotational symmetries as a function of the bias field orientation originating from the strong modulation of internal field distribution at different regions of such unorthodox system. The experimentally observed spin wave modes have been qualitatively well reproduced by micromagnetic simulations and the simulated mode profiles unravel the presence of diverse genres of extended and localized standing modes in these unusual magnonic crystals. These observations are significant for tunability and anisotropic propagation of spin waves leading towards the development of efficient magnonic devices competent with the future microwave communication systems. [ABSTRACT FROM AUTHOR]

The Mn-Ge binary system has been intensively studied because of a variety of phases with intriguing magnetic properties. Here, we report the thin film fabrication of two types of Mn3Ge by employing Pt and Ru seed layers. Our structural analysis, in addition to magnetic and transport measurements, have revealed that the Mn3Ge film with the Pt layer has γ-Mn type cubic structure. This is in contrast to the Mn3Ge film with Ru seed layer, which posseses D022 tetragonal structure. Pt/Mn3Ge also exhibits antiferromagnetic properties, including the exchange bias effect with the blocking temperature of TB ∼ 350 K. [ABSTRACT FROM AUTHOR]

The Weyl antiferromagnet Mn3Sn has been recently attracting significant attention as it exhibits various useful functions such as a large anomalous Hall effect that is normally absent in antiferromagnets. Here, we report the thin film fabrication of the single phase of Mn3Sn and the observation of the large anomalous Hall effect at room temperature despite its vanishingly small magnetization. Our work on the high-quality thin film growth of the Weyl antiferromagnet paves the path for developing antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

Ultrafast spin dynamics in ferromagnetic nanodot arrays with dot diameter 100 nm and thickness 20 nm arranged in honeycomb and octagonal lattice symmetries are studied to explore the tunability of the collective magnetization dynamics. By varying the inter-dot separation between 30 nm and 300 nm drastic variation in the precessional dynamics from strongly collective to completely isolated regime has been observed by using all-optical time-resolved magneto-optical Kerr microscope. Micromagnetic simulation is exploited to gain insights about the resonant mode profiles and magnetic coupling between the nanodots. A significant spectral and spatial variation in the resonant mode with increasing dipolar interaction is demonstrated with increasing inter-dot separation. The spins driven by effective field inside single nanodots are prone to precess independently, generating two self-standing centre and edge modes in the array that are influenced by the relative orientation between the inter-dot coupling direction and bias magnetic field. The anisotropic behavior of dipolar field is rigorously investigated here. Splitting of the centre mode in case of octagonal lattice is experimentally observed here as a consequence of the anisotropic dipolar field between the nanodot pairs coupled horizontally and vertically, which is not found in the honeycomb lattice. In addition, proper understanding of the modification of dynamic mode profile by neighboring dipolar interaction built up here, is imperative for further control of the dynamic dipolar interaction and the corresponding collective excitation in magnonic crystals. The usage of nanodot lattices with complex basis structures can be advantageous for the designing of high density magnetic recording media, spin-wave filter and logic devices. [ABSTRACT FROM AUTHOR]