Electron-Nuclear Double Resonance and Relaxation in RbMnF3

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Abstract
Electron‐nuclear double resonance has been observed in RbMnF3 at liquid‐helium temperatures. Nuclear saturation, which was induced by applying a large amplitude UHF signal to the sample, was detected as a shift in the field required for AFMR at x‐band frequencies. With the field applied in the [100] direction, saturation could be induced by pumping either the low‐field or spin‐flop modes. For a given x‐band frequency, the effective nuclear temperatures for the low‐field and spin‐flop modes were in substantial agreement. The range of pumping frequency over which saturation could be induced was roughly 100 MHz, (≤686 MHz), and was a function of the Mn55 resonant frequency. Extrapolation of the experimental data to infinite nuclear temperature yields a value of 686.5 MHz for the unpulled nuclear hyperfine frequency, which agrees well with the value obtained from direct NMR experiments. Measurements of the saturation decay yielded a value of 50 msec for T1 at 4.2°K.