Imagine that a metallic wire is attached to a part of a large insulator, which itself exhibits no magnetization. It seems impossible for electrons in the wire to register where the wire is positioned on the insulator. Here we found that, using a Ni₈₁Fe₁₉/Pt bilayer wire on an insulating sapphire plate, electrons in the wire recognize their position on the sapphire. Under a temperature gradient in the sapphire, surprisingly, the voltage generated in the Pt layer is shown to reflect the wire position, although the wire is isolated both electrically and magnetically. This non-local voltage is due to the coupling of spins and phonons: the only possible carrier of information in this system. We demonstrate this coupling by directly injecting sound waves, which realizes the acoustic spin pumping. Our finding provides a persuasive answer to the long-range nature of the spin Seebeck effect, and it opens the door to 'acoustic spintronics' in which sound waves are exploited for constructing spin-based devices.

Superconductivity of nanosized Pb-island structures whose radius is 0.8 to 2.5 times their coherence length was studied under magnetic fields using low-temperature scanning tunneling microscopy and spectroscopy. Spatial profiles of superconductivity were obtained by conductance measurements at zero-bias voltage. Critical magnetic fields for vortex penetration and expulsion and for superconductivity breaking were measured for each island. The critical fields depending on the lateral size of the islands and existence of the minimum lateral size for vortex formation were observed.

When energy is introduced into a region of matter, it heats up and the local temperature increases. This energy spontaneously diffuses away from the heated region. In general, heat should flow from warmer to cooler regions and it is not possible to externally change the direction of heat conduction. Here we show a magnetically controllable heat flow caused by a spin-wave current. The direction of the flow can be switched by applying a magnetic field. When microwave energy is applied to a region of ferrimagnetic Y3Fe5O12, an end of the magnet far from this region is found to be heated in a controlled manner and a negative temperature gradient towards it is formed. This is due to unidirectional energy transfer by the excitation of spin-wave modes without time-reversal symmetry and to the conversion of spin waves into heat. When a Y3Fe5O12 film with low damping coefficients is used, spin waves are observed to emit heat at the sample end up to 10 mm away from the excitation source. The magnetically controlled remote heating we observe is directly applicable to the fabrication of a heat-flow controller.

A platinum (Pt)/yttrium iron garnet (YIG) bilayer system with a well-controlled interface has been developed; spin mixing conductance at the Pt/YIG interface has been studied. Crystal perfection at the interface is experimentally demonstrated to contribute to large spin mixing conductance. The spin mixing conductance is obtained to be 1.3 × 10 18 m −2 at the well-controlled Pt/YIG interface, which is close to a theoretical prediction.

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The force sensor is key to the performance of atomic force microscopy (AFM). Nowadays, most atomic force microscopes use micromachined force sensors made from silicon, but piezoelectric quartz sensors are being applied at an increasing rate, mainly in vacuum. These self-sensing force sensors allow a relatively easy upgrade of a scanning tunneling microscope to a combined scanning tunneling/atomic force microscope. Two fundamentally different types of quartz sensors have achieved atomic resolution: the "needle sensor," which is based on a length-extensional resonator, and the "qPlus sensor," which is based on a tuning fork. Here, we calculate and measure the noise characteristics of these sensors. We find four noise sources: deflection detector noise, thermal noise, oscillator noise, and thermal drift noise. We calculate the effect of these noise sources as a factor of sensor stiffness, bandwidth, and oscillation amplitude. We find that for self-sensing quartz sensors, the deflection detector noise is independent of sensor stiffness, while the remaining three noise sources increase strongly with sensor stiffness. Deflection detector noise increases with bandwidth to the power of 1.5, while thermal noise and oscillator noise are proportional to the square root of the bandwidth. Thermal drift noise, however, is inversely proportional to bandwidth. The first three noise sources are inversely proportional to amplitude while thermal drift noise is independent of the amplitude. Thus, we show that the earlier finding that quoted an optimal signal-to-noise ratio for oscillation amplitudes similar to the range of the forces is still correct when considering all four frequency noise contributions. Finally, we suggest how the signal-to-noise ratio of the sensors can be improved further, we briefly discuss the challenges of mounting tips, and we compare the noise performance of self-sensing quartz sensors and optically detected Si cantilevers.

The influence of high pressures of carbon monoxide (CO) on the stability of a Au/Ni(111) surface alloy has been studied by high-pressure scanning tunneling microscopy. We show that CO induces a phase separation of the surface alloy at high pressures, and by means of time-lapsed STM movies we find that Ni atoms are removed from the surface layer during the process. Density functional theory calculations reveal the thermodynamic driving force for the phase separation to be the Au-induced compression of the CO overlayer with a resulting CO-CO repulsion. Furthermore, the atomistic mechanism of the process is shown to be kink-site carbonyl formation and evaporation which is found to be enhanced by the presence of Au.

In a previous Letter [1], Jensen et al. investigated the high-pressure (200-750 torr) response of the Pt(111) surface towards carbon monoxide using scanning tunneling microscopy (STM). A new hexagonal CO overlayer structure was found, quite different from the structures formed at similar coverages under low pressure and temperature conditions, and Jensen et al. concluded that their results illustrated the inequivalence between studies of surfaces in catalytic conditions of high pressure and surface science studies carried out in high vacuum.In this Comment, we present atomically resolved STM images obtained at room temperature with a novel highpressure STM described elsewhere [2]. Our results differ from those obtained by Jensen et al. in several respects: At 1 bar of CO, we detect two rotational domains of a hexagonal CO Moiré pattern with a periodicity of 11.8 6 0.4 Å A B C FIG. 1. (A) STM image ͑240 3 125͒ Å 2 of two rotational domains of the Moiré pattern formed at 1 bar CO. (B) Highresolution STM image ͑55 3 51͒ Å 2 of the CO overlayer obtained at 1 bar CO. (C) The ͑ p 19 3p 19͒ R23.4 ± -13 CO structure. One CO molecule in the unit cell has been fixed in the on-top position. If, alternatively, the CO molecule is fixed to the bridge or fcc position, the energy is raised by about 0.4 eV per unit cell (three-layer Pt slab). The unit cell of the pattern is indicated with the solid line. Dark balls represent CO molecules adsorbed in nearly on-top sites (see text). rotated C 24 6 2 ± with respect to the underlying substrate (see Fig. 1A). This alone invalidates the model proposed in [1] consisting of a nonrotated CO overlayer. Furthermore, we resolve the individual CO molecules of the overlayer structure and find that the Moiré pattern arises from a ͑ p 19 3 p 19͒R23.4 ± -13 CO unit cell, corresponding to a surface coverage of 0.68 ML (Fig. 1B). From an interplay between our STM results and density functional calculations, we arrive at the lowest-energy structural model shown in Fig. 1C with 13 CO molecules per unit cell. The brightest protrusions in Fig. 1B are associated with CO in on-top adsorption sites.At low pressure and temperature conditions (170 K), we moreover observe the exact same CO Moiré structure when the Pt(111) surface is saturated with CO. This result is consistent with earlier low-temperature LEED studies [3]. 170 K is thus a sufficiently high temperature to overcome the CO diffusion barrier and facilitate long-range ordering, and yet sufficiently low to form high-coverage saturation structures. (At 90 K we observe a kinetically hindered domain structure.)Comparing the high-pressure CO structural model presented in Fig. 1C with the c͑4 3 2͒-2CO roomtemperature UHV saturation structure (u 0.5 ML), a 47% on-top occupancy increase is found. In this way our STM results are in excellent agreement with a recent sum-frequency generation study by Rupprechter et al., who observed a ϳ40% on-top occupancy increase when the CO pressure was raised from low to high pressure [4].With respect to the so-called p...