SQUID Measurements of the Susceptibilities of Impurity-Helium Condensates

For the first time, the magnetic susceptibilities of impurity-helium condensates containing magnetic impurities have been measured via a SQUID magnetometer in the temperature range between 1.1 and 2.1 K. The impurity-helium condensates are gel-like aggregates of nanocrystallites composed of molecules and free radicals. Molecular oxygen nanocrystals and atomic nitrogen embedded in molecular N2 nanocrystals have been studied. The susceptibilities of the samples containing nitrogen atoms followed Curie-Weiss behavior with very small Weiss temperatures ranging from +0 to −0.4 K. The behavior of samples composed of O2 nanocrystals deviated sharply from the results for bulk solid O2. The susceptibility of the samples was 102 larger than for bulk solid O2 and showed Curie-Weiss behavior with a Weiss temperature in the range from −4.5 to −5 K. This result is qualitatively consistent with results obtained in other laboratories for O2 confined in restricted geometries.