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Register a new userOn-chip detection of ferromagnetic resonance of a single submicron permalloy strip
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We measured ferromagnetic resonance of a single submicron ferromagnetic strip, embedded in an on-chip microwave transmission line device. The method used is based on detection of the oscillating magnetic flux due to the magnetization dynamics, with an inductive pick-up loop. The dependence of the resonance frequency on applied static magnetic field agrees very well with the Kittel formula, demonstrating that the uniform magnetization precession mode is being driven.
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Permalloy films with one-dimensional (1D) profile modulation of submicron periodicity are fabricated based on commercially available DVD-R discs and studied using ferromagnetic resonance (FMR) method and micromagnetic numerical simulations. The main resonance position shows in-plane angular dependence which is strongly reminiscent of that in ferromagnetic films with uniaxial magnetic anisotropy. The main signal and additional low field lines are attributed to multiple standing spin wave resonances defined by the grating period. The results may present interest in magnetic metamaterials and magnonics applications.
The dynamic magnetic susceptibility of magnetic materials near ferromagnetic resonance (FMR) is very important in interpreting dc-voltage in electrical detection of FMR. Based on the causality principle and the assumption that the usual microwave absorption lineshape around FMR is Lorentzian, general forms of dynamic susceptibility of an arbitrary sample and the corresponding dc-voltage lineshape are obtained. Our main findings are: 1) The dynamic susceptibility is not a Polder tensor for material with arbitrary anisotropy. Two off-diagonal elements are not in general opposite to each other. However, the linear response coefficient of magnetization to total rf field is a Polder tensor. This may explain why two off-diagonal elements are always assumed to be opposite to each other in analyses. 2) The frequency dependence of dynamic susceptibility near FMR is fully characterized by six numbers while its field dependence is fully characterized by seven numbers. 3) A recipe of how to determine these numbers by standard microwave absorption measurements for an arbitrary sample is proposed. Our results allow one to unambiguously separate the contribution of the anisotropic magnetoresistance to dc-voltage from that of the anomalous Hall effect. With these results, one can reliably extract the information of spin pumping and the inverse spin Hall effect, and determine the spin-Hall angle. 4) The field-dependence of susceptibility matrix at a fixed frequency may have several peaks when the effective field is not monotonic of the applied field. In contrast, the frequency-dependence of susceptibility matrix at a fixed field has only one peak. Furthermore, in the case that resonance frequency is not sensitive to the applied field, the field dependence of susceptibility matrix, as well as dc-voltage, may have another non-resonance broad peak. Thus, one should be careful in interpreting observed peaks.
We have suspended an Al based single-electron transistor whose island can resonate freely between the source and drain leads forming the clamps. In addition to the regular side gate, a bottom gate with a larger capacitance to the SET island is placed underneath to increase the SET coupling to mechanical motion. The device can be considered as a doubly clamped Al beam that can transduce mechanical vibrations into variations of the SET current. Our simulations based on the orthodox model, with the SET parameters estimated from the experiment, reproduce the observed transport characteristics in detail.
We demonstrate nuclear magnetic resonance (NMR) spectroscopy of picoliter-volume solutions with a nanostructured diamond chip. Using optical interferometric lithography, diamond surfaces were nanostructured with dense, high-aspect-ratio nanogratings, enhancing the surface area by more than a factor of 15 over mm^2 regions of the chip. The nanograting sidewalls were doped with nitrogen-vacancy (NV) centers so that more than 10 million NV centers in a (25 micrometer)^2 laser spot are located close enough to the diamond surface (5 nm) to detect the NMR spectrum of 1 pL of fluid lying within adjacent nanograting grooves. The platform was used to perform 1H and 19F NMR spectroscopy at room temperature in magnetic fields below 50 mT. Using a solution of CsF in glycerol, we demonstrate that 4 +/- 2 x 10^12 19F spins in a 1 pL volume, can be detected with a signal-to-noise ratio of 3 in 1 s integration. This represents nearly two orders of magnitude improvement in concentration sensitivity over previous NV and picoliter NMR studies.
The magnetization characteristic in a permalloy thin strip is investigated by electrically measuring the anisotropic magnetoresistance and ferromagnetic resonance in in-plane and out-of-plane configurations. Our results indicate that the magnetization vector can rotate in the film plane as well as out of the film plane by changing the intensity of external magnetic field of certain direction. The magnetization characteristic can be explained by considering demagnetization and magnetic anisotropy. Our method can be used to obtain the demagnetization factor, saturated magnetic moment and the magnetic anisotropy.
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