Critical behavior of Ga[sub 1-x]Mn[sub x]As

Abstract

The temperature dependencies of the resistivity, the magnetization, the specific heat and the thermal diffusivity have been conducted in the close vicinity of magnetic phase transition in Ga1‐xMnxAs. Two different types of Ga1‐xMnxAs samples have been investigated. The sample with a Mn concentration of 1.6% shows an insulating behavior and the sample with a Mn concentration of 2.6% is metallic. From the M(T) and M(H) curves by using Arrott plots the Curie temperature and the critical exponents of β, γ, and δ have been determined. The temperature dependencies of the specific heat and thermal diffusivity of Ga1‐xMnxAs samples demonstrated a pronounced λ shaped peak, which indicates an existence of a second‐order phase transition in these samples. The specific heat peak maximum is located near the Curie temperature and therefore, it is attributed to the ferromagnetic‐paramagnetic phase transition. From detailed analysis of the specific heat and the thermal diffusivity data above and below TC, the value of critical exponent α has been determined. The critical behavior of the specific heat of Ga1‐xMnxAs samples is well described by the mean‐field including Gaussian fluctuations model.