Температура магнитного упорядочения оксида трехвалентного железа varepsilon-Fe-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

The trivalent iron oxide ε-Fe_2O_3 is a fairly rare polymorphic iron oxide modification, which only exists in the form of nanoparticles. This magnetically ordered material exhibits an intriguing magnetic behavior, specifically, a significant room-temperature coercivity H _C (up to ~20 kOe) and a magnetic transition in the temperature range of 80–150 K accompanied by a sharp decrease in the H _C value. Previously, the temperature of the transition to the paramagnetic state for ε-Fe_2O_3 was believed to be about 500 K. However, recent investigations have shown that the magnetically ordered phase exists in ε-Fe_2O_3 also at higher temperatures and, around 500 K, another magnetic transition occurs. Using the data on the magnetization and temperature evolution of the ferromagnetic resonance spectra, it is shown that the temperature of the transition of ε-Fe_2O_3 particles 3–10 nm in size to the paramagnetic state is ~850 K.