Structural and magnetic properties of a new type of ordered oxygen-deficient perovskite, KMnVO4

A new ternary vanadate KMnVO4 was prepared by a solid-state reaction and was shown to be a new type of ordered oxygen-deficient perovskite ABO3 - with = 1/3. Its formula can be rewritten as (K2,Mn)[Mn,V2]O8 1. An ordered distribution of potassium and manganese atoms in the A site and of vanadium and manganese atoms in the B site is observed. The manganese atoms are in distorted octahedral and tetrahedral sites, whereas all of the vanadium atoms form VO43- tetrahedra. This oxide contains four different types of high-spin Mn2+ ions in equal number. Magnetic susceptibility and specific heat measurements as well as spin dimer analysis show that substantial antiferromagnetic spin-exchange interactions occur primarily among three of the four different types of Mn2+ ions, and the fourth Mn2+ ion remains paramagnetic down to 2 K