A broadband Ferromagnetic Resonance dipper probe for magnetic damping measurements from 4.2 K to 300 K

TL;DR

This paper introduces a broadband FMR dipper probe capable of precise magnetic damping measurements from 4.2 K to 300 K, featuring a novel probe head and stable temperature control for improved accuracy.

Contribution

It presents a new broadband FMR probe design with enhanced stability, signal-to-noise ratio, and temperature control, enabling accurate damping measurements across a wide temperature range.

Findings

Successful Gilbert damping measurements on thin films up to 26 GHz

Demonstrated stable operation from 4.2 K to room temperature

Achieved high signal-to-noise ratio with the new probe design

Abstract

A dipper probe for broadband Ferromagnetic Resonance (FMR) operating from 4.2 K to room temperature is described. The apparatus is based on a 2-port transmitted microwave signal measurement with a grounded coplanar waveguide. The waveguide generates a microwave field and records the sample response. A 3-stage dipper design is adopted for fast and stable temperature control. The temperature variation due to FMR is in the milli-Kelvin range at liquid helium temperature. We also designed a novel FMR probe head with a spring-loaded sample holder. Improved signal-to-noise ratio and stability compared to a common FMR head are achieved. Using a superconducting vector magnet we demonstrate Gilbert damping measurements on two thin film samples using a vector network analyzer with frequency up to 26 GHz: 1) A Permalloy film of 5 nm thickness and 2) a CoFeB film of 1.5 nm thickness. Experiments were performed with the applied magnetic field parallel and perpendicular to the film plane.