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Current flowing through heavy metals generates spin current by the spin Hall effect (SHE), and spin current exerts a torque on the adjacent magnetic layer, thereby switching the magnetization direction of the magnetic layer. Normally, an external magnetic field must be used to break symmetry in the response to the SHE torque, to realize deterministic switching. However, the presence of magnetic fields increases the difficulty in integrating spintronic devices with complementary metal-oxide-semiconductor. Thus, field-free spin–orbit torque switching has been a research hotspot. Here, symmetry-breaking has been realized by tilting the sample during the annealing process, resulting in a non-uniform diffusion of Ta atoms in the samples along the temperature gradient (x-direction), which was confirmed by transmission electron microscope mapping. As a result, the sample has demonstrated deterministic switching, in the absence of an external magnetic field, with a switching ratio of up to 88% and the critical current density of 1.5 × 107 A/cm2. Tilting annealing is a simple approach to achieve field-free switching. [ABSTRACT FROM AUTHOR]

An electrically conductive metal typically transmits or absorbs a spin current. Here, we report on evidence that interfacing two metal thin films can suppress spin transmission and absorption. We examine spin pumping in spin-source/spacer/spin-sink heterostructures, where the spacer consists of metallic Cu and Cr thin films. The Cu/Cr spacer largely suppresses spin pumping—i.e., neither transmitting nor absorbing a significant amount of spin current—even though Cu or Cr alone transmits a sizable spin current. The antiferromagnetism of Cr is not essential for the suppression of spin pumping, as we observe similar suppression with Cu/V spacers with V as a nonmagnetic analog of Cr. We speculate that diverse combinations of spin-transparent metals may form interfaces that suppress spin pumping, although the underlying mechanism remains unclear. Our work may stimulate a new perspective on spin transport in metallic multilayers. [ABSTRACT FROM AUTHOR]

This document is a study conducted by a group of first-year engineering students on the magnetic gyro wheel toy. The study aimed to build a model of the toy and analyze its physics. The document presents equations and calculations to determine the necessary angular velocity and holding force of the wheel. The students found the assignment challenging but inspiring, and the document suggests further investigations and questions for discussion. The author, Bjarne Schmidt, is an experienced physics and mathematics teacher at the University of Southern Denmark. [Extracted from the article]

A spin Hall effect (SHE) enables the electrical generation and detection of spin currents for promising applications in spintronics, but heavy metals with low spin Hall angle θSH limit the development of SHE devices. In this work, we have introduced dielectric oxide material SrTiO3 into Pt by magnetron sputtering and measured the θSH on the NiCo/Pt1–x(STO)x heterostructure through spin-torque ferromagnetic resonance. Our results demonstrate that the maximum spin Hall angle in Pt0.98(STO)0.02 is 0.121 ± 0.003, which is approximately twice that of pure Pt (0.064 ± 0.003). Moreover, theoretical analysis has revealed that the spin Hall angle arises from a complementary interplay between intrinsic and extrinsic mechanisms, namely, the strong spin–orbit coupling in Pt for the intrinsic mechanism and side-jump scattering caused by scalar potential and lattice expansion at dielectric impurities for the extrinsic mechanism. This interplay significantly contributes to enhancing the spin Hall angle. This work demonstrates an effective strategy for fabricating high-performance spin Hall materials with low resistivity, large spin Hall angle, and excellent compatibility with semiconductor processes in low-power spin-torque devices. [ABSTRACT FROM AUTHOR]

Faraday rotation is considered a gold standard measurement of the electronic spin polarization of an alkali metal vapor produced under optical pumping. However, during the production of large volumes of hyperpolarized xenon gas, transmission monitoring measurements, otherwise known as field cycling measurements, are generally employed to measure the spin polarization of alkali metal atoms in situ as this method is easier to implement than Faraday rotation on standard polarizer setups. Here, we present a simple, low-cost experimental setup to perform Faraday rotation measurements of the electronic spin polarization of alkali metal atoms that can be easily implemented on standard polarizer setups. We then compare Rb polarization measurements obtained with the Faraday rotation method to those obtained with the transmission monitoring method. To our knowledge, a direct comparison of these methods has never been made. Overall, we found good agreement between the two methods, but at low Rb density and high laser power, we found evidence of nonlinear magneto-optical effects that may prevent Faraday rotation from being used under these conditions. [ABSTRACT FROM AUTHOR]

Most spin caloritronics research utilizes thin films on substrates with an in-plane heat flow, where an unintended out-of-plane thermal gradient may develop by heat dissipation through the substrate. In systems exploiting metallic ferromagnets to generate or detect spin currents, such out-of-plane thermal gradients might confuse the signal via undesirable thermomagnetic effects, such as the anomalous Nernst effect. Here, we report direct measurement of the spin current created by the spin Nernst effect in platinum, using ferromagnetic metal contacts as spin accumulation detectors. By comparing the voltage measured transverse and longitudinal to the thermal gradient, we find that the device geometry is crucial in all-metallic systems. Exploiting the orthogonality in the angular dependence on the external magnetic field of the transversely measured voltage, we quantitatively separate the spin Nernst signal from the parasitic anomalous Nernst voltage, which are of the same order of magnitude. As a result, we estimate the spin Nernst angle of platinum to be comparable to the spin Hall angle in magnitude with an opposite sign. [ABSTRACT FROM AUTHOR]

In an easy-plane antiferromagnet with the Dzyaloshinskii–Moriya interaction (DMI), magnons are subject to an effective spin-momentum locking. An in-plane temperature gradient can generate interfacial accumulation of magnons with a specified polarization, realizing the magnon thermal Edelstein effect. We theoretically investigate the injection and detection of this thermally driven spin polarization in an adjacent heavy metal with a strong spin Hall effect. We find that the inverse spin Hall voltage depends monotonically on both temperature and the DMI but non-monotonically on the hard-axis anisotropy. Counterintuitively, the magnon thermal Edelstein effect is an even function of a magnetic field applied along the Néel vector. [ABSTRACT FROM AUTHOR]

We have analyzed the relative energy of nonmagnetic and magnetic low-lying electronic states of Ni atoms adsorbed on regular and defective sites of the MgO(001) surface. To this end cluster and periodic surface models are used within density functional theory. For Ni atoms adsorbed on oxygen vacancies at low coverage, the interaction energy between the metal and the support is much larger than on regular sites. Strong bonding results in a diamagnetic adsorbed species and the energy required to reach the high-spin state increases. Moreover, a correlation appears between the low-spin to high-spin energy difference and the interaction energy hypothesizing that it is possible to prepare the surface to tune the high-spin to low-spin energy difference. Magnetic properties of adsorbed thin films obtained upon increasing coverage are more difficult to interpret. This is because the metallic bond is readily formed and dominates over the effect of the atoms directly bound to the vacancy. [ABSTRACT FROM AUTHOR]

By first principles method, we have determined the geometric configuration of K/Ba-codoped phenanthrene based on the formation energy calculations, and systematically investigated its electronic and magnetic properties. There are two bands crossing Fermi energy which mainly result from the LUMO+1 orbitals of two phenanthrene molecules in a unit cell, and the cylinder-like Fermi surface along the Γ - Z direction reflects the two-dimension character of metallic conduction of K/Ba-codoped phenanthrene. Compared to K-doped phenanthrene, K/Ba-codoping can donate more electrons to molecule to modify the electronic structure, while the intercalation of dopants does not result in the large distortion of molecule. (KBa)1phenanthrene is a magnetic metal with the spin moment of 0.32 μB per each molecule, and unexpectedly, the spins gather in one edge of molecule rather than a uniform distribution on the whole molecule. Our results demonstrate that codoping of monovalent and bivalent metals is an effective approach to modulate the electronic properties of metal-doped hydrocarbons. [ABSTRACT FROM AUTHOR]

Inserting a thin (t[sup *]=0.5 or 1 nm) layer of the antiferromagnet FeMn into the “free” Permalloy (Py) layer of a sputtered, current-perpendicular exchange-biased spin valve, Nb/FeMn/Py (pinned)/Cu/Py (free)/Nb, is shown to enhance AΔR, the difference in specific resistance between the states where the magnetizations of the two Py layers are parallel and antiparallel to each other. Such an increase is taken as evidence that spin-memory loss (spin relaxation) due to the FeMn is strong, and that judicious insertion of a source of spin relaxation into a multilayer with high specific resistance contacts can enhance AΔR, the numerator of the magnetoresistance. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Memory effect has been observed in both standard top and bottom spin valves. The change of the magnetization state in the pinned FM layer, below the blocking temperature, reverses the direction of the exchange bias and destroys the magnetoresistance properties. This reversed exchange bias is much weaker, causing severe consequences in SV applications. This behavior can be explained in terms of blocking temperature distribution in the AFM layer perhaps due to the structural randomness. By varying cooling procedures, the exchange coupling in regions with different blocking temperatures can be separated. It is found that the maximum exchange bias is very close to the sum of the exchange biases in different regions. The domain wall energy in the FM layer has to be taken into account in order to explain the behavior of the reversed bias. The insertion of a synthetic antiferromagnetic subsystem (Co/Ru/Co) stabilizes the magnetization state in the pinned layer because of the additional interlayer coupling through the Ru layer. This suppresses the memory effect. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The ferromagnetic compound Nd[sub 5]Fe[sub 17] has a large average Fe moment (2.1 μ[sub B]), a reasonably high Curie temperature (503 K), but basal plane spin orientation. Partial replacement of Nd by Sm leads to a uniaxial spin arrangement with substantial anisotropy field. Natural Sm has a large neutron absorption cross section (5650 b) which is usually thought to prevent neutron diffraction measurements unless Sm is replaced by a separated isotope with low absorption. However, the unique geometry of the MURR neutron powder diffractometer allows measurements on thin samples and data have been successfully collected on samples with up to about 50% Sm (Nd[sub 2.5]Sm[sub 2.5]Fe[sub 17]). Samples prepared without Ti contain the 2:17 phase as well as the 5:17 phase, while those prepared with Ti have a very high concentration of the 5:17 phase which forms more readily (with minor amounts of TiFe[sub 2]). The locations of Sm atoms in these compounds have been determined. These results may provide important information about the crystal fields at different sites in the 5:17 phase and suggest improved routes for synthesis of this potentially useful compound. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present the results of optical measurements on the structures containing GaAs/AlGaAs quantum wells with positively charged acceptors (A+ centers). The data on the spin structure and localization of the A+ centers in the 2D system were obtained using magneto-optical measurements. The energy structure of the A+ impurity band was studied using the temperature dependence of photoluminescence. Based on the analysis of the complete set of experimental data obtained by different optical methods and their comparison with the results of transport measurements reported in literature, we developed a unified physical picture of charge and spin phenomena in such systems. A new experimental method, based on the measurements of photoexcitation and photoluminescence spectra, is proposed for studies of the Coulomb gap appearing at low temperatures in the density of localized states. [ABSTRACT FROM AUTHOR]

We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings. [ABSTRACT FROM AUTHOR]

Nanocomposite ribbons with composition Pr10(Fe1-2xCoxNix)84B6 (x = 0.0, 0.05, 0.10, and 0.15) were prepared by melt-spinning. All melt-spun ribbons are composed of a fine mixture of 2:14:1 and bcc-(Fe,Co,Ni) phases with an additional soft phase (Pr2Fe23B3-based) for x = 0.10 and 0.15. The room temperature coercivity decreases from 7.4 to 2 kOe with Co and Ni substitutions likely due to the decrease of the magnetocrystalline anisotropy of the 2:14:1 phase and the increase of the amount of the soft phases. Saturation magnetization increases slightly while remanence and (BH)max show a slight decrease for x up to 0.10 and then they drop quickly. The intergranular exchange coupling is strong for x ≤ 0.10 but it is reduced significantly for x = 0.15 due to the substantial increase of the volume and size of the soft phases. Thermomagnetic measurements showed a significant increase of the Curie temperature of the 2:14:1 phase from 290 °C for x = 0 to 485 °C for x = 0.15. High temperature hysteresis loop measurements showed improved temperature dependence of remanence and coercivity for x = 0.05. [ABSTRACT FROM AUTHOR]

Presents an abstract of the study 'Spin Fluctuations of La[sub2-x]Sr[subx]Cu[sub1-y]Zn[suby]O[sub4-δ] (x=0.14, y=0.012),' by M. Matsuda, K. Kuroda, K. Yamada, Y. Endoh, H. Chou, G. Shirane, R. J. Birgeneau, M. A. Kastner, I. Tanaka, and H. Kojima.