A convenient way of determining the ferromagnetic transition temperature of metallic (Ga,Mn)As

We have studied magnetic and transport properties of insulating and metallic (Ga,Mn)As layers before and after annealing. A dramatic increase of the ferromagnetic transition temperature TC by postgrowth annealing has been realized in both insulating and metallic (Ga,Mn)As. The as-grown insulating (Ga,Mn)As can be turned into metallic by the low-temperature annealing. For all the metallic (Ga,Mn)As, a characteristic feature in the temperature dependence of sheet resistance appears around TC. This phenomenon may provide a simple and more convenient method to determine the TC of metallic (Ga,Mn)As compared with superconducting quantum interference device (SQUID) measurement. Moreover, the TC of the metallic (Ga,Mn)As obtained by this way is in good agreement with that measured by a SQUID magnetometer.