Suppression of the N\'eel temperature in hydrothermally synthesized alpha-Fe2O3 nanoparticles

摘要: Magnetic measurements up to 1000 K have been performed on hydrothermally synthesized $\alpha$-Fe$_{2}$O$_{3}$ nanoparticles (60 nm) using a Quantum Design vibrating sample magnetometer. A high vacuum environment (1$\times$10$^{-5}$ torr) during the magnetic measurement leads complete reduction of Fe$_{3}$O$_{4}$. This precludes determination N\'eel temperature for nanoparticles. In contrast, coating with SiO$_{2}$ stabilizes phase 930 K, which allows us determine first time. The 60-nm is found be 945 about 15 below bulk value. small consistent finite-size scaling theory. Our current results also show that can effectively protect from oxidation or reduction, important technological applications.