We have made a crossed coil setup (X and Y transmit/receiving coils) with a SQUID pick up loop along Z.
Now we want to see EPR or NMR lines, probably using it in a CW fashion, ie. putting a ramp + lock-in oscillation in X, a CW excitation frequency in Y and demodulating the SQUID signal in Z.
Question is: What sample will give us nice, narrow, distinguishable lines at 4°K?.
Note: we can only go up to 10 mT with the X coil. Liquid $^3$He is off our budget.