Specific Heat Study of GaMnAs

Specific heat was used to study the magnetic phase transition in GaMnAs. Two types of samples were investigated. The sample with a Mn concentration of 1.6% shows an insulating behavior whereas the sample with a Mn concentration of 2.6% is metallic. The temperature dependence of the specific heat for both samples reveals a lambda-shaped peak near the Curie temperature, which indicates a second-order phase transition is occuring in these samples. The critical behavior of the specific heat for the GaMnAs samples is consistent with the mean-field behavior with Gaussian fluctuations of the magnetization in the vicinity of TC.