We are currently doing a variable-frequency single-crystal study of a compound with Mn as the only magnetic ion. I have discovered an unexpected isotropic signal at g = 1.7. It appears at all frequencies and is independent of the direction of the applied field. I expect all signals from my compound to depend on the direction of the applied magnetic field. Thus, I expect that the signal at g=1.7 is an impurity of an origin unknown to me. Do any of you have suggestions?
If you are in a quartz EPR tube(particularly one that you flame sealed yourself), or mounted on a quartz rod, my best guess would be a quartz radical defect. Though g=1.7 is a bit low, I thought it should be closer to g=1.9, so it could be a result of sample position or field/frequency mis-calibration.
I would acquire an EPR spectrum with the same resonator, sample tube and crystal holder, but without the crystal. If the signal is still there, it's not from the crystal, and you don't need to worry about it if it's not overlapping with your crystal spectrum.