On-chip detection of ferromagnetic resonance of a single submicron Permalloy strip

Abstract

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.Recent discoveries of novel phenomena in mesoscopic systems containing nanomagnets pave the way to new spintronics devices 1,2,3 . Brataas et al. 4 proposed a new application of ferromagnetic resonance (FMR), a so-called spin battery. In such a device, a spin current flows into a paramagnetic metal from its interface with a precessing ferromagnet, which is resonantly driven with an rf magnetic field. A number of experiments 5,6,7,8,9,10 , have been used to measure FMR on thin ferromagnetic films or on ensembles of small ferromagnets. This work measured rf-power transmission or absorption with a coplanar waveguide with ferromagnetic material on top of it, or with ferromagnetic material in a microwave cavity.

Electrical detection of spin pumping: dc voltage generated by ferromagnetic resonance at ferromagnet/nonmagnet contact

“…6͑b͔͒ gives ␥ = 176 GHz/ T, and N ʈ 0 M S = 60 mT, N Ќ 0 M S = 930 mT, consistent with earlier reports. 26,43 The fit confirms that the dc voltage appears at the uniform ferromagnetic resonance mode of the Py strip. The measured amplitude of the dc voltage as a function of the square of the applied rf current, at 13 GHz and 139 mT is shown in Fig.…”

“…We have recently shown that a submicron Py strip can be driven into the uniform precession ferromagnetic resonance mode 21,26 by using a small perpendicular rf magnetic field created with an on-chip coplanar strip waveguide 39 ͑CSW͒ positioned close to Py strip ͑similar geometry as shown in Fig. 3͒.…”

“…A way to periodically change the magnetization direction is to put F into FMR, where circular precession of the magnetization can be resonantly excited by a small applied rf magnetic field. 21,26 The transfer of spin angular momentum by the precessing magnetization of F in contact with N ͑spin pumping͒ was first described 9 using the formalism of parametric charge pumping 27 developed in the context of mesoscopic scattering problems. The main points of this description are discussed below.…”

Dispersion and spin wave “tunneling” in nanostructured magnetostatic spin waveguides

“…Ferromagnetic wires with magnetization, wave vector k, and biasing magnetic field H aligned along the wire have been explored theoretically 10,11 while elegant and powerful Brillouin light scattering experiments document thermally excited lateral standing wave patterns associated with the various spin wave modes. [12][13][14] Here we use shorted coplanar waveguides 15,16 to excite and detect BVMSWs in spin waveguides and directly measure the spin wave dispersion and attenuation. Further, we document spin wave "tunneling" through gaps in the wires produced by focused ion beam ͑FIB͒ etching.…”

Electrical Detection of Spin Pumping due to the Precessing Magnetization of a Single Ferromagnet

“…We have recently shown [12] that a submicron Py strip can be driven into the uniform precession ferromagnetic resonance mode, using a small perpendicular rf magnetic field created with an on-chip coplanar strip waveguide [13] positioned close to the Py strip (similar geometry as shown in Fig. 1).…”