Abstract:We investigated a possible use of the magnonic interferometric switches in multi-valued logic circuits. The switch is a three-terminal device consisting of two spin channels where input, control, and output signals are spin waves. Signal modulation is achieved via the interference between the source and gate spin waves. We report experimental data on a micrometer scale prototype based on Y 3 Fe 2 (FeO 4 ) 3 structure. The output characteristics are measured at different angles of the bias magnetic field. The On/Off ratio of the prototype exceeds 36 dB at room temperature. Experimental data is complemented by the theoretical analysis and the results of micro magnetic simulations showing spin wave propagation in a micrometer size magnetic junction. We also present the results of numerical modeling illustrating the operation of a nanometersize switch consisting of just 20 spins in the source-drain channel. The utilization of spin wave interference as a switching mechanism makes it possible to build nanometerscale logic gates, and minimize energy per operation, which is limited only by the noise margin. The utilization of phase in addition to amplitude for information encoding offers an innovative route towards multi-state logic circuits. We describe possible implementation of the three-value logic circuits based on the magnonic interferometric switches. The advantages and shortcomings inherent in interferometric switches are also discussed.2

Silicon's weak intrinsic spin-orbit coupling and centrosymmetric crystal structure are a critical bottleneck to the development of Si spintronics, because they lead to an insignificant spin-Hall effect (spin current generation) and inverse spin-Hall effect (spin current detection).Here, we undertake current, magnetic field, crystallography dependent magnetoresistance and magneto-thermal transport measurements to study the spin transport behavior in freestanding Si thin films. We observe a large spin-Hall magnetoresistance in both p-Si and n-Si at room temperature and it is an order of magnitude larger than that of Pt. One explanation of the unexpectedly large and efficient spin-Hall effect is spin-phonon coupling instead of spin-orbit coupling. The macroscopic origin of the spin-phonon coupling can be large strain gradients that can exist in the freestanding Si films. This discovery in a light, earth abundant and centrosymmetric material opens a new path of strain engineering to achieve spin dependent properties in technologically highly-developed materials.

We propose and demonstrate a technique for magnetic microstructure imaging via their interaction with propagating spin waves. In this approach, the object of interest is placed on top of a magnetic testbed made of material with low spin wave damping. There are micro-antennas incorporated in the testbed. Two of these antennas are used for spin wave excitation while another one is used for the detecting of inductive voltage produced by the interfering spin waves. The measurements are repeated for different phase differences between the spin wave generating antennas which is equivalent to changing the angle of illumination. The collected data appear as a 3D plotthe holographic image of the object. We present experimental data showing magnonic holographic images of a low-coercivity Si/Co sample, a high-coercivity sample made of SrFe 12 O 19 and a diamagnetic copper sample. We also present images of the three samples consisting of a different amount of SrFe 12 O 19 powder. The imaging was accomplished on a Y 3 Fe 2 (FeO 4) 3 testbed at room temperature. The obtained data reveal the unique magnonic signatures of the objects. Experimental data is complemented by the results of numerical modeling, which qualitatively explain the characteristic features of the images. Potentially, magnonic holographic imaging may complement existing techniques and be utilized for non-destructive in-situ magnetic object characterization. The fundamental physical limits of this approach are also discussed.

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