# EPR or NMR sample that will give narrow lines at 4 K

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.

• Come on, homework? You should be able to propose a few, and make educated guesses at their linewidth!
– Karl
Jul 8 '19 at 22:31
• @ Karl, I'm a physicist... I dont know many commonly used EPR samples. If its worth anything, we did try teflon NMR and copper sulfate EPR and they both failed. Jul 9 '19 at 5:35
• A search using g-standard and/or single line epr might help. In the worse case O am pretty sure you can ask an author and you will get advice in minutes. Jul 9 '19 at 11:19
• I'm amazed someone gave you access to LHe cryogenic equipment for this. Have you tried if your EPR works at room temperature? Btw. the abbreviation "EPR" and "CW fashion" don't fit.
– Karl
Jul 9 '19 at 19:09
• I'm amazed someone gave you access to LHe cryogenic equipment for this.- It actually belongs to me, I use cryogens on a daily basis so I wouldn't be so amazed. Btw. the abbreviation "EPR" and "CW fashion" don't fit. - How about "Continuous Wave EPR" as contrast to "Pulsed EPR"? Jul 10 '19 at 6:48