The spin diffusion length for thermally excited magnon spins is measured by utilizing a non-local spin-Seebeck effect measurement. In a bulk single crystal of yttrium iron garnet (YIG) a focused laser thermally excites magnon spins. The spins diffuse laterally and are sampled using a Pt inverse spin Hall effect detector. Thermal transport modeling and temperature dependent measurements demonstrate the absence of spurious temperature gradients beneath the Pt detector and confirm the non-local nature of the experimental geometry. Remarkably, we find that thermally excited magnon spins in YIG travel over 120 µm at 23 K, indicating that they are robust against inelastic scattering. The spin diffusion length is found to be at least 47 µm and as high as 73 µm at 23 K in YIG, while at room temperature it drops to less than 10 µm. Based on this long spin diffusion length, we envision the development of thermally powered spintronic devices based on electrically insulating, but spin conducting materials.2

The longitudinal spin Seebeck effect refers to the generation of a spin current when heat flows across a normal metal/magnetic insulator interface. Until recently, most explanations of the spin Seebeck effect use the interfacial temperature difference as the conversion mechanism between heat and spin fluxes. However, recent theoretical and experimental works claim that a magnon spin current is generated in the bulk of a magnetic insulator even in the absence of an interface. This is the so-called intrinsic spin Seebeck effect. Here, by utilizing a non-local spin Seebeck geometry, we provide additional evidence that the total magnon spin current in the ferrimagnetic insulator yttrium iron garnet (YIG) actually contains two distinct terms: one proportional to the gradient in the magnon chemical potential (pure magnon spin diffusion), and a second proportional to the gradient in magnon

Self-assembly and light-induced mechanical switching of azobenzene derivatives deposited on GaAs(110) were explored at the single molecule level using scanning tunneling microscopy (STM). 3,3′,5,5′-Tetra-tert-butylazobenzene (TTB-AB) molecules in the trans isomer configuration were found to form well-ordered islands on GaAs(110). After exposure to ultraviolet (UV) light, the TTB-AB molecules exhibited conformational changes attributed to trans to cis photoisomerization. Photoisomerization of TTB-AB/GaAs is observed to occur preferentially in one-dimensional (1D) stripes. This 1D cascade behavior differs significantly from optically induced switching behavior observed when TTB-AB molecules are placed on a gold surface.

Spin currents are generated within the bulk of magnetic materials due to heat flow, an effect called intrinsic spin-Seebeck. This bulk bosonic spin current consists of a diffusing thermal magnon cloud, parametrized by the magnon chemical potential (µm), with a diffusion length of several microns in yttrium iron garnet (YIG). Transient opto-thermal measurements of the spin-Seebeck effect (SSE) as a function of temperature reveal the time evolution of µm due to intrinsic SSE in YIG. The interface SSE develops at

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