We report measurements of the spin torque efficiencies in perpendicularly magnetized Pt/Co bilayers where the Pt resistivity ρPt is strongly dependent on thickness tPt. The dampinglike spin Hall torque efficiency per unit current density ξDLj varies significantly with tPt, exhibiting a peak value ξDLj=0.12 at tPt=2.8-3.9 nm. In contrast, ξDLj/ρPt increases monotonically with tPt and saturates for tPt>5 nm, consistent with an intrinsic spin Hall effect mechanism, in which ξDLj is enhanced by an increase in ρPt.

Highly parallel graphics processing units (GPUs) can improve the speed of micromagnetic simulations significantly as compared to conventional computing using central processing units (CPUs). We present a strategy for performing GPU-accelerated micromagnetic simulations by utilizing cost-effective GPU access offered by cloud computing services with an open-source Python-based program for running the MuMax3 micromagnetics code remotely. We analyze the scaling and cost benefits of using cloud computing for micromagnetics. © 2015 Elsevier B.V.

We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 μm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity.

We report measurements of the in-plane magnetoelastic coupling in both as-deposited and annealed ultrathin Ta/CoFeB/MgO layers as a function of uniaxial strain, conducted using a four-point bending apparatus. While as-deposited samples show only a weak dependence of the magnetoelastic coupling on the CoFeB layer thickness in the ultrathin regime (<2nm), we observe the onset of a strong thickness dependence upon annealing. This dependence can be modeled as arising from a combination of effective surface and volume contributions to the magnetoelastic coupling.

Coherent gigahertz-frequency surface acoustic waves (SAWs) traveling on the surface of a piezoelectric crystal can, via the magnetoelastic interaction, resonantly excite traveling surface spin waves in an adjacent thin-film ferromagnet. These excited surface spin waves, traveling with a definite in-plane wave-vector q∥ enforced by the SAW, can be detected by measuring changes in the electro-acoustical transmission of a SAW delay line.

We report that spin current transport across Pt/ferromagnet (FM) interfaces as measured by the spin torques exerted on the FM is strongly dependent on the type and the thickness of the FM layer and on post-deposition processing protocols. By employing both harmonic voltage measurements and spin-torque ferromagnetic resonance measurements, we find that the efficiency of the Pt spin Hall effect in exerting a dampinglike spin torque on the FM corresponds to an effective spin Hall ratio ranging from <0.05 to >0.10 under different interfacial conditions.

We report a strong enhancement of the efficacy of the spin Hall effect (SHE) of Pt for exerting anti-damping spin torque on an adjacent ferromagnetic layer by the insertion of ?0.5?nm layer of Hf between a Pt film and a thin, ≤2?nm, Fe60Co20B20 ferromagnetic layer. This enhancement is quantified by measurement of the switching current density when the ferromagnetic layer is the free electrode in a magnetic tunnel junction.

Using polarization-resolved photoluminescence spectroscopy, we investigate the breaking of valley degeneracy by an out-of-plane magnetic field in back-gated monolayer MoSe2 devices. We observe a linear splitting of -0.22meV/T between luminescence peak energies in σ+ and σ- emission for both neutral and charged excitons. The optical selection rules of monolayer MoSe2 couple the photon handedness to the exciton valley degree of freedom; so this splitting demonstrates valley degeneracy breaking.

The technological appeal of multiferroics is the ability to control magnetism with electric field1-3. For devices to be useful, such control must be achieved at room temperature. The only single-phase multiferroicmaterial exhibiting unambiguousmagnetoelectric coupling at room temperature is BiFeO3 (refs 4 and 5). Its weak ferromagnetismarises fromthe canting of the antiferromagnetically aligned spins by the Dzyaloshinskii-Moriya (DM) interaction6-9.

We model, using the macrospin approximation, the magnetic reversal of a perpendicularly magnetized nanostructured free layer formed on a normal, heavy-metal nanostrip, subjected to spin-orbit torques (SOTs) generated by short (≤0.5ns) current pulses applied to the nanostrip, to examine the potential for SOT-based fast, efficient cryogenic memory.