A Wideband Spectrometer for NMR Studies

The design of a wideband decimeter-wave (200 - 900 MHz) spectrometer with a magnetic induction of up to ~ 10 T is described. This spectrometer is intended for studying electronic - nuclear oscillations in antiferromagnets at low temperatures (4.2 - 1.3 K). Critical field H_c = 2.5 +/- 0.3 T of a reorientation transition in a noncollinear antiferromagnet Mn3Al2Ge3O12 at temperature T = 1.3 K was determined from a 55Mn2+ NMR spectrum.