High-temperature properties of the Sr2FeMoO6 double perovskite: Electricalresistivity, magnetic susceptibility, and ESR

In this work we present electrical resistivity, magnetic susceptibility, an d electron spin resonance data at high temperature of the Sr2FeMoO6 double perovskite. We found between 300 K and 900 K two metal-insulator transition temperatures at T(c)approximate to 405 K and approximate to 590 K respecti vely. Below the first transition, the material is metallic and magnetically ordered. Above 590 K, rho shows a metallic behavior again, while in the ra nge 405 K less than or equal to T less than or equal to 590 K we observed a weak localization. The magnetic susceptibility can be described taking int o account localized and itinerant electrons. The paramagnetic resonance of Fe3+ ions with g = 2.009(5) can be studied in temperature. Above T-c the li newidth data present similar behavior to that of manganese perovskites, wit h a relaxation mechanism related to spin-spin interactions. The intensity o f the resonance line decreases with T faster than a Curie law expected, due to a reduction in the number of localized spins of the Fe3+ ions. At high temperatures (T greater than or equal to 520 K) we observe a second paramag netic resonance line with g=1.995(1) associated with a small amount of Mo5 ions.