UC Irvine

This master dissertation investigates detection of microwave signals by magnetic tunnel junctions(

MTJs) as sensing elements. The detection is based on the spin-torque diode eect.

First, we show a wireless detection of microwave signals using a MTJ based detector. This

MTJ detector is integrated with compact coplanar waveguide antennas and non-magnetic,

microwave-transparent, reusable antenna holder. We compare the experimental results with

MTJs of dierent magnetic layer structures. The tested structures can achieve comparable

sensitivities to those of commercial semiconductor, diode-based microwave sensors. The detection

frequencies can be tuned by a permanent magnet attached to the detector. Second,

we demonstrate a microwave frequency determination method by a pair of MTJs as microwave

detectors. A resonance-type spin-torque microwave detector (STMD) can be used

to determine the frequency of an input microwave signal. But the accuracy is limited by

the STMD's ferromagnetic resonance linewidth. By applying a pair of uncoupled STMDs

connected in parallel to a microwave signal source, we show that the accuracy of frequency

measurement is improved signicantly.