Structures, chemical states and properties of Sr₂Fe_1+xMo_1−xO₆ ceramics sintered in N₂

Abstract

Abstract We report that the Fe-rich single-phase Sr 2 Fe 1+ x Mo 1− x O 6 ( x = 1/9, 1/6 and 1/3) ceramics can be synthesized in a N 2 stream by the solid-state reaction method, while the usual Sr 2 FeMo 2 O 6 (i.e. x = 0) can only be synthesized in a H 2 +Ar stream. X-ray diffraction shows that all ceramics are well crystallized with tetragonal symmetry. X-ray photoelectron spectroscopy results confirm that the chemical states of interior Fe and Mo cations are significantly more complex than those of the surface cations. With the increase in x , the materials change from ferrimagnetic ( x = 0, 1/9, 1/6) to spin-glass-like behaviour ( x = 1/3) and the magnetism decreases dramatically. The Curie temperature ( T c ) and the magnetoresistance (MR) at 10 K with a field of 2 T ( T c , MR) are (400 K, −20.9%), (390 K, −10.3%) and (385 K, −4.5%) for x = 0, 1/9 and x = 1/6, respectively. The results are further analysed by Monte Carlo simulations. Our results show that high- T c ferrimagnetic double perovskites with good magnetic and transport properties can be obtained conveniently in a N 2 stream instead of conventional H 2 +Ar, which not only provides a safe and low-cost way to synthesize these materials, but may also be helpful in decreasing the oxygen vacancy concentration.