Pulsed inductive microwave magnetometer developed at NIST. (News Briefs).

As part of its program in high-speed magnetics, NIST has developed an automated, pulsed inductive microwave magnetometer (PIMM) to characterize magnetic thin films. The PIMM is designed to measure the magnetodynamical properties of materials used in recording heads for magnetic data storage. The data storage industry is developing new magnetic alloys with high saturation magnetization to use in write heads. The magnetic damping behavior of these new alloys will determine their usefulness for high-speed recording.

The PIMM uses a co-planar 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 rise-time pulse generator. Orthogonal Helmholtz coils provide the magnetic bias and saturating fields required for the measurement. A 20 GHz digital sampling oscilloscope is used to acquire the data. The system can measure dynamical behavior as a function of several variables, including applied bias field, pulsed field amplitude and width, and sample orientation. Using fast Fourier transforms, the PIMM can determine the frequency dependence of the complex magnetic permeability as well as the step and impulse responses of magnetic systems.

The PIMM includes components necessary for completely automated magnetodynamic measurements. No user intervention is required to insert or remove attenuators on the front end of the high-bandwidth sampling oscilloscope. This reduces the chance of an electrostatic discharge that could damage the sensitive front-end circuitry of the oscilloscope. It also increases the system sensitivity since the attenuators can be set in finer increments to give the largest signal as the pulse amplitude is adjusted.

This unique magnetometer has been used by visiting scientists from university data storage research centers and disk drive manufacturers.

CONTACT: Ron Goldfarb, [phone]; [e-mail].