Modified Electron Paramagnetic Resonance System (for FMR) - diagram

A modified Varian electron paramagnetic resonance (EPR) spectrometer is used with a klystron to do ferromagnetic resonance (FMR) spectroscopy in the X-band (9.53 GHz). The magnetic sample to be measured is placed between the poles of an electromagnet, at the end of a shorted waveguide or centered in a cavity. An incident microwave signal couples to the sample and is partially absorbed. A crystal detector then measures the reflected microwave signal. This signal from the crystal detector is then input into the lock-in amplifier where it is compared with the reference signal. The output voltage from the lock-in amplifier vs. the external magnetic field corresponds to the derivative of the absorption curve. The half power linewidth and magnetic resonance field can be then found easily.