Magnetic and electrical properties of BaSrMMoO6 (M = Mn, Fe, Co, and Ni)

Abstract

The remarkable transformation of the magnetic properties of four double perovskite oxides has been studied, while the crystal structure remains unchanged between the four compounds. BaSrFeMoO6 is known to be ferrimagnetically ordered. However, our work indicates that BaSrMnMoO6, BaSrCoMoO6, and BaSrNiMoO6 are all antiferromagnetic, where the Neel temperature increases systematically as a function of the transition metal. The transition to the antiferromagnetic state occurs below 6 K, 30 K, and 75 K for the Mn, Co, and Ni compounds, respectively. We have also performed X-ray photoelectron spectroscopy (XPS) studies on all four compounds. The XPS indicates that BaSrMnMoO6 and BaSrFeMoO6 contain molybdenum in the pentavalent state, while Mn and Fe are trivalent. The situation is different for BaSrCoMoO6 and BaSrNiMoO6, which contain hexavalent molybdenum and divalent cobalt and nickel. It should be noted that the Mn and Fe compounds can only be synthesized in 5% H2/Ar balance, while BaSrCoMoO6 and BaSrNiMoO6 can be made in pure argon. Furthermore, we have examined the electrical conductivities of all four materials in the temperature range 25–800 °C to further highlight the contrast between the Fe compound, which has a metal-like behavior, and the Mn, Co, and Ni analogs, which are semiconductors.