Магнетизм в наноразмерных порошках ферромолибдата стронция

Single-phase nanosized Sr 2 FeMoO 6- δ powders were synthesized by citrate-gel method at pH = 4, 6, 9, with various degrees of superstructural ordering of Fe 3+ and Mo 5+ cations ( P = 65 % for pH = 4, P = 51 % for pH = 6 and P = 20 % for pH = 9). According to the XPS analysis results, mixed valence state of cations iron and molybdenum was established. With increasing of pH, the Fe 2+ concentration value rises from 63 % to 72 %, whereas the Fe +3 concentration drops from 37 % to 28 %. According to the results of investigations of magnetization temperature dependence performed in ZFC (zero-field cooling) and FC (field cooling) modes a metastable superparamagnetic state in low-dimensional grains of Sr 2 FeMoO 6- d ferrimagnetic powders at T < 19 K was established. In powders with pH = 4 the number of low dimensional grains is significantly larger than powders with pH = 6 and 9. This has led to their large magnetization value at T = (4,2-19) K.