Anthony B. Kos, John P. Nibarger, Radek Lopusnik, Thomas J. Silva, Zbigniew J. Celinski
A cryogenic pulsed inductive microwave magnetometer is used to characterize the switching dynamics in thin-film materials at low temperatures and microwave frequencies. The system is contained inside a 20-cm-dia ultrahigh vacuum chamber and cooled by a cryopump that allows measurements between 20 and 350 K. A temperature controller regulates the sample temperature using two silicon diodes as sensors. Applied magnetic fields of up to 36 kA/m (450 Oe) are generated by a four-pole, water-cooled electromagnet with independent control of each axis. Magnetic switching is driven by high-speed current step pulses in a coplanar waveguide structure with the sample placed in a flip-chip configuration. A 20 GHz sampling oscilloscope is used to record the dynamics of the magnetic reorientation. The switching dynamics are given for a 10-nm thick Ni-Fe film at 30 K in response to a 1 kA/m field step.