Structural and magnetic properties of mixed valent Ca2MnTiO6

Abstract

The compound Ca₂MnTiO₆, synthesized using a two-step solid-state reaction method, has been studied for its structural, spectroscopic (XPS) and magnetic properties, as part of our efforts to understand the correlation between mixed metal oxide bonds and magnetism in double perovskite oxides. Room temperature diffraction studies shows that the compound is in orthorhombic structure at room temperature and remains so till low temperatures, although the variation in global instability index (GII) indicated little instability of the structure as the temperature is lowered from room temperature (∼300 K) to 3 K. The compound exhibits interesting behavior in magnetic susceptibility, as it exhibits magnetization reversal or negative magnetic susceptibility at low applied fields which turns positive for higher fields. Magnetic susceptibility also exhibits two anomalies at T_N1 ∼ 8.2 K and another one around, T_N2, between 121 – 124 K. Magnetization as a function of field reveals weak antiferromagnetism in the system, as M varies non-linearly, but sluggishly below T<150 K, with no signature of saturation with respect to H. Overall, magnetization studies show that there is inherent magnetic frustration in the system and lack of long-range magnetic order, which is supported by low temperature neutron diffraction studies too. The XPS studies quantify the oxidation states of mixed valent Mn and Ti. A comparison of the structural and physical properties of double perovskite compound is presented here to understand the strong correlation between structural, spectroscopic and magnetic properties.