High-temperature properties of the 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 (Formula presented) double perovskite. We found between 300 K and 900 K two metal-insulator transition temperatures at (Formula presented) K and (Formula presented) K respectively. Below the first transition, the material is metallic and magnetically ordered. Above 590 K, (Formula presented) shows a metallic behavior again, while in the range (Formula presented) we observed a weak localization. The magnetic susceptibility can be described taking into account localized and itinerant electrons. The paramagnetic resonance of (Formula presented) ions with (Formula presented) can be studied in temperature. Above (Formula presented) 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 (Formula presented) ions. At high temperatures (Formula presented) K) we observe a second paramagnetic resonance line with (Formula presented) associated with a small amount of (Formula presented) ions.