We have performed both zero field and high transverse field measurements at dilution refrigerator temperatures on a number of heavy electron systems, examining the superconducting and magnetic properties of these interesting materials. Among the materials studied to date are UBe
13, URu
2Si
2 and U
6Fe. The magnetic field penetration depth in the superconducting state of UBe
13 is greater than 10000 Å, as no increase in the transverse field relaxation rate is observed below
T c . A sharp increase in the precession frequency is seen, starting at
T c . This frequency shift shows little temperature dependence at low temperature; we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu
2Si
2 show the weak antiferromagnetic transition at 17.5 K. Finally, we we found no clear evidence for unconventional superconductivity in this material. Zero field measurements in URu
2Si
2 show the weak antiferromagnetic transition at 17.5 K. Finally, we have observed relaxation in high transverse field due to the formation of a flux lattice in U
6Fe, a material where the electron effective mass is rather lighter than in other heavy fermion systems. The relaxation exhibits a sharp onset at
T c=3.9 K, and is flat at low temperatures as expected for a conventional superconductor.
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