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

In this work we present electrical resistivity, magnetic susceptibility, and 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 respectively. Below the first transition, the material is metallic and magnetically ordered. Above 590 K, rho shows a metallic behavior again, while in the range 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 into 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 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 Fe3+ ions. At high temperatures (T greater than or equal to 520 K) we observe a second paramagnetic resonance line with g=1.995(1) associated with a small amount of Mo5+ ions.