14N nuclear quadrupole resonance of p-nitrotoluene using a high-Tc rf SQUID

Using a high-T-c radio-frequency superconducting quantum interference device (rf SQUID), we successfully detected nuclear quadrupole resonance (NQR) at about 887 kHz for N-14 in p-nitrotoluene (PNT). A normal metal transformer made of copper wire was used to improve the sensitivity of the high-T-c rf SQUID and pulse-controlled rf switches and cross diodes were inserted in the transformer to reduce the influence of the strong excitation field. The preliminary results for NQR detection using the high-T-c SQUID had a similar signal-to-noise ratio to that of using a low noise preamplifier.