Strain-dependent magnetic anomalies in dopedUPt3

An anomaly at 6 K in the magnetic susceptibility and the specific heat is found in ${\mathrm{UPt}}_3$ doped both by Pd on the Pt sites and by Th on the U sites. The compositional behavior of the anomaly, with $T_{\mathrm{anomaly}}$ essentially constant for certain compositions (0.04≤x≤0.08 for Pd and 0.1≤x≤0.2 for Th) and falling rapidly at higher or lower concentrations, is unusual. With the use of field measurement of the specific-heat and the susceptibility data, the anomaly appears to be due to antiferromagnetism. This long-range order is found to be quite strain sensitive, disappearing upon grinding, just as found for superconductivity in pure ${\mathrm{UPt}}_3$. A simple model that encompasses all the data is proposed to explain the behavior of the anomaly.