Specific heat of the magnetic glass system LaAl2:Gd between 0.5 K and 20 K

Specific heat measurements between 0.55 K and 20 K were performed on the alloy system LaAl2:Gd for Gd concentrations of 0.0, 1.0, 2.0, 3.0, and 6.0 atomic percent. The specific heat in external fields up to 4900 Oe was also studied. At low temperatures broad peaks associated with the magnetic ordering of the randomly-distributed Gd ions are observed, characteristic of a class of dilute magnetic alloys known as magnetic or spin glasses. For pure LaAl2 a superconducting transition was observed at 3.290K, but the sample was normal down to 1.30K for applied fields greater than 850 Oe. For temperatures below about 60K, the normal state specific heat is described by the equation C = (0.631 +- 0.1)/T2 + (10.08 +- 0.05)T + (0.124 +- 0.001)T3 millijoules/mole-K. For all values of applied field used, the specific heat data indicates the onset of magnetic order at some temperature T/sub m/, implying that the anomalous field-dependent behavior observed in previous magnetic resonance measurements is due to the way in which this technique samples the spin system