Pulsed inductive microwave magnetometer

Abstract

We describe the apparatus, software, and measurement procedures for a pulsed inductive microwave magnetometer (PIMM). PIMM can measure the dynamical properties of materials used in recording heads for magnetic storage applications, and it can be used as a general magnetodynamics diagnostic tool. PIMM uses a coplanar waveguide as both a source of fast pulsed magnetic fields and as an inductive flux sensor. Magnetic field pulses are provided by a 10 V, 55 ps risetime pulse generator; a 20 GHz digital sampling oscilloscope is used to acquire the fast pulse data; and orthogonal Helmholtz pairs provide the bias and saturating fields required for the measurement. The system can measure dynamical behavior as a function of several variables, including applied magnetic bias field, magnetic pulsed field amplitude and width, and sample orientation. Using a fast Fourier transform, PIMM can determine the frequency dependence of the complex magnetic permeability, as well as the step and impulse responses of the magnetic system. Data from 50 nm Ni–Fe and rare-earth-doped Ni–Fe thin films are presented.