Highly Sensitive Ferromagnetic Resonance Measurements Using Coplanar Waveguides

Abstract

Ferromagnetic resonance (FMR) measurements using coplanar waveguides (CPWs) make it possible to perform highly sensitive magnetization measurements, since a CPW can concentrate electromagnetic waves onto a narrow signal line. In this study, we aimed to perform FMR measurements of a minute individual magnet, and investigated the dependence of the sensitivity on the signal line width. We fabricated CPWs on MgO wafers and placed an individual NiFe dot on each of CPWs. NiFe dots with a thickness of 30 nm and various lateral sizes, i.e. 50 × 100, 50 × 80, 50 × 30, 50 × 20, and 50 × 10 m, were fabricated. The signal line widths of these samples were 150, 100, 50, 30, and 15 m, respectively. The external magnetic field dependence of the resonance frequency was well fitted by Kittel's formula. As expected, we obtained larger signals from smaller samples, because narrower signal lines that create larger rf fields were employed for smaller samples.

Effect of Doping Elements on the Damping Constant of $({\hbox {Ni-Fe}})_{1-{ x}}{\hbox {M}}_{ x}$ (${\hbox {M}}={\hbox {Ga}}$, Ag, Mo, and W) Films

“…Details of this process to obtain are reported elsewhere [6], [7]. Note that inhomogeneous broaden-ing of caused by as anisotropy field dispersion which may be influential to estimation of was considered to be negligible since an external magnetic field was applied up to 20 kA/m during the resonance measurement and was strong enough to magnetically saturate the films.…”

“…Using this CPW, was evaluated by the CPW-FMR method with a sweeping frequency (0.1-20 GHz) in a various external magnetic field (0-79.6 kA/m) applied parallel to this CPW plane. Details of the method are described later in this paper and also in [6] and [7].…”

Tunnel Magnetoresistance and Spin-Transfer-Torque Switching in PolycrystallineCo2FeAlFull-Heusler-Alloy Magnetic Tunnel Junctions on AmorphousSi/

“…The Gilbert damping parameter, , is a critical parameter for determining the critical current density of STT switching. In order to examine  for the polycrystalline CFA film, demagnetization field (H d ), and magnetic damping parameter ( H ), respectively, estimated by fitting each spectrum using an analytical solution [42]. Here, we assume the gyromagnetic ratio () as 2 × 0.00297 GHz/Oe and neglect the in-plane magnetic anisotropic field.…”

Experiments on Microwave-Assisted Magnetization Reversal in a Submicron-Scale Permalloy Single Element with a Zero-Field Resonance Frequency of 6.3 GHz

“…To improve the detectable intensity of the ferromagnetic resonance (FMR) absorption of the NiFe element in the CPW, it is important to reduce the width of the center conductor of the CPW. 8) In this study, the width of the center conductor could be narrowed up to the pattern width of the NiFe element by means of a lift-off method followed by Ar ion milling with a precise control of the milling depth. The sample was prepared as follows: An electrically shorted CPW consisting of Ti (10 nm)/Au (50 nm)/Ti (10 nm)/ NiFe (35 nm)/Au (10 nm) was first fabricated on a glass substrate by the conventional lift-off method.…”