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We use the dipolar fields from a magnetic cantilever tip to generate localized spin wave precession modes in an in-plane magnetized, thin ferromagnetic film. Multiple resonances from a series of localized modes are detected by ferromagnetic resonance force microscopy and reproduced by micromagnetic models that also reveal highly anisotropic mode profiles. Modeled scans of line defects using the lowest-frequency mode provide resolution predictions of (94.5±1.5) nm in the field direction, and (390±2) nm perpendicular to the field.

The comment of M. Weiler et al.[1] raises a pertinent question about the origin of the electrical signal detected in our letter [2], reporting on the detection of the ac part of the spin-pumping current emitted during ferromagnetic resonance using the inverse spin Hall effect (ac-ISHE). The originality of our method was to induce a resonance in YIG|Pt at half the frequency using parametric excitation in the parallel geometry. Other attempts to measure the ac-ISHE have used a balanced circuit [3], spin rectification effects [4] or phase detection [5]. M. Weiler et al. point out to an inconsistency in the interpretation of our data: if indeed the uniform mode of our YIG would be excited, then the produced ferromagnetic inductive (FMI) voltage should have dominated over the ac-ISHE voltage and it should have lead to the same signal amplitude in both YIG|Pt and YIG|Al. In ref.[2], we report a signal in YIG|Pt that is about an order of magnitude smaller than the predicted FMI-voltage and the signal vanishes in the case of YIG|Al, where only the FMI-voltage should dominate.Because we missed the estimation of the expected FMI contribution, we have revisited exhaustively [6] our measurement of the ratio, ρ, between the signal measured in the YIG|Pt and YIG|NM, where NM is a normal metal suppressing the ISHE. We present in FIG.1 two sets of measurements performed near the onset of the parametric excitation. We first show in panel (b) and (c), a comparison of the signal measured in YIG|Pt 7nm and in YIG|Pt 7nm |Al 50nm [7]. The two sets are performed at the same YIG location, ensuring that the parametric threshold is unchanged. Although increasing the NM thickness reduces the impedance of the circuit, this should enhance the FMI-part of the signal. This method thus yields an under-estimation of the ratio ρ = |V iSHE + V FMI |/|V FMI |. Comparing the two samples, we find that the ratio ρ is larger than 5 when P ≤ 24 dBm. The disappearance of the signal above 3 GHz is due to the fact that the stripline becomes there inefficient to pump parametrically the YIG. In order to check the influence of the impedance match, we have repeated the measurement in another YIG sample covered by three electronically connected slabs of respectively Pt 7nm , Al 15nm and Pt 7nm

Measuring local magnetization dynamics and its spatial variation is essential for advancements in spintronics and relevant applications. Here we demonstrate a phase-sensitive imaging technique for studying patterned magnetic structures based on picosecond laser heating. With the timeresolved anomalous Nernst effect (TRANE) and extensions, we simultaneously image the dynamic magnetization and RF driving current density. The stroboscopic detection implemented in TRANE microscopy provides access to both amplitude and phase information of ferromagnetic resonance (FMR) and RF current. Using this approach, we measure the spatial variation of the Oersted driving field angle across a uniform channel. In a spatially nonuniform sample with a cross shape, a strong spatial variation for the RF current as well as FMR precession is observed. We find that both the amplitude and the phase of local FMR precession are closely related to those of the RF current.

Transparent e-skin that can fully mimic human skin with J-shaped mechanical-behavior and tactile sensing attributes have not yet been reported. In this work, the skin-like hydrogel composite with J-shaped mechanical behavior and highly transparent, tactile, soft but strong, flexible, and stretchable attributes is developed as structural strain sensing element for e-skin. Piezo-resistive polyacrylamide (PAAm) hydrogel is used as supporting matrix to endow high transparency, softness, flexibility, stretch-ability and strain sensing capability desired for e-skin. Ultrahigh molecular weight polyethylene (UHMWPE) fiber with a wavy configuration is designed as reinforcement filler to provide the tunable strain-limiting effect. As a result, the as-prepared UHMWPE fiber/PAAm composite e-skin presents unique “J-shape” stress–strain behavior akin to human skin. And the PAAm composite can switch from supersoft to highly stiff in the designed strain range up to 100% with a prominent tensile strength of 48.3 MPa, which enables it to have the high stretch-ability and excellent load-bearing ability, simultaneously. Moreover, finite element model is developed to clarify the stress distribution and damage evolution for the UHMWPE fiber/PAAm composite during the tensile process. The PAAm composite exhibits not only an excellent strain sensing performance with a long-term reliability up to 5000 loading–unloading cycles but also an extraordinary softness and mechanical strength with a low initial modulus of 6.7 kPa, which is matchable with soft human epidermis. Finally, the e-skin is used for demonstrations in monitoring various human activities and protecting structural integrity in designed strain ranges. The strategy for reinforcing piezo-resistive hydrogel with wavy-shaped UHMWPE fibers proposed here is promising for the development of transparent, flexible, soft but strong e-skin with a tunable strain-limiting effect akin to human skin.

Magnetic field noise from magnons can reduce the lifetimes of proximate spins and degrade the performance of spin based technologies. However, spatial and temporal averaging over the area of typical field sensors makes measuring magnetic field noise challenging. Here, we use an ensemble of nitrogen-vacancy (NV) point-defects in diamond to measure the spectral profile of thermally excited spinwave noise at room temperature as a function of the distance away from a 20 nm thick Permalloy (Py) thin film. We systematically vary the separation between the NV and Py layers using a silicon-dioxide wedge and measure the longitudinal relaxation rate of the NV center ms = 0 state as a function of the separation. The measured spinwave-induced relaxation of an ensemble of NV centers is well described by a magnetostatic model of dipole fields from the spinwaves. We furthermore find that our all-optical, nonperturbative measurements of the spinwave noise can be used to extract information about the ferromagnetic source, such as magnetization, damping, and fluctuating amplitude. This technique is amenable to application with stand-off from ferromagnetic elements and from buried structures.

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