In this work we present electrical resistivity, magnetic susceptibility, and electron spin resonance data at high temperature of the Sr 2 FeMoO 6 double perovskite. We found between 300 K and 900 K two metalinsulator transition temperatures at T c Ϸ405 K and Ϸ590 K respectively. Below the first transition, the material is metallic and magnetically ordered. Above 590 K, shows a metallic behavior again, while in the range 405 KрTр590 K we observed a weak localization. The magnetic susceptibility can be described taking into account localized and itinerant electrons. The paramagnetic resonance of Fe 3ϩ ions with gϭ2.009(5) can be studied in temperature. Above T c the linewidth data present similar behavior to that of manganese perovskites, with a relaxation mechanism related to spin-spin interactions. The intensity of the resonance line decreases with T faster than a Curie law expected, due to a reduction in the number of localized spins of the Fe 3ϩ ions. At high temperatures (Tу520 K͒ we observe a second paramagnetic resonance line with gϭ1.995(1) associated with a small amount of Mo 5ϩ ions.

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