High pressure synthesis of ilmenite and perovskite type MnVO3 and their magnetic properties

Ilmenite and perovskite type Mn2+V4+O3 are newly synthesized at high pressures and high temperatures. The low pressure form of MnVO3 I is supposed to have a trichlinic symmetry and to be isomorphous with the vanadate ilmenites CoVO3 I and CuVO3 I. Unit cell dimensions are a = 5.072 (5) Å, b = 5.550 (5) Å, c = 5.023 (4) Å, α = 90°0′ (6′), β = 118°38′ (4′), γ = 63°4′ (4′) and V = 106.3 (1) Å3. The high pressure form of MnVO3 II, stabilized above about 45 kbar, has the orthorhombic perovskite structure with the possible space group of D162h-Pbnm or C92v-Pbn21. Unit cell dimensions are a = 5.106 (1) Å, b = 5.265 (1) Å, c = 7.387 (1) and V = 198.6 (1) Å3. MnVO3 II is the first perovskite containing Mn2+ ions in the larger cationic sites in the perovskite structure. Magnetic and electric properties of both MnVO3 I and II are studied. Magnetic susceptibilities of both substances obey the Curie-Weiss law. Weak ferromagnetic moments are found in both substances at low temperatures. MnVO3 I shows semiconducting behaviour, whereas MnVO3 II relatively low electric resistivity.