Heterodyne detection of alternating magnetic fields with a resonating xylophone bar magnetometer

A resonating xylophone bar magnetometer has been utilized as the mixer in a heterodyne detector for variable-frequency alternating magnetic fields. To illustrate the range of this detection scheme, examples offered include the response to low frequency, sinusoidal magnetic fields at 2, 10, and 20 Hz and to high frequency sinusoidal magnetic fields in the MHz regime. In a final example, the response of the magnetometer to the field generated by a 20 Hz square wave has been compared to the Fourier components of an idealized square wave, with no apparent loss in sensitivity and a mean deviation from expected values of less than 0.5%.