Structural and magnetic properties of Pr18Li8Fe5−xMxO39 (M=Ru, Mn, Co)

A polycrystalline sample of Pr18Li8Fe4RuO39 has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mössbauer spectroscopy; samples of Pr18Li8Fe5−xMnxO39 and Pr18Li8Fe5−xCoxO39 (x  =1, 2) have been studied by magnetometry. All these compounds adopt a cubic structure (space group Pm3¯n, a0∼11.97 Å) based on intersecting 〈111〉 chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Pr–O framework. The trigonal-prismatic site in Pr18Li8Fe4RuO39 is occupied by Li+ and high-spin Fe3+. The remaining transition-metal cations occupy the two crystallographically-distinct octahedral sites in a disordered manner. All five compositions adopt a spin-glass-like state at 7 K (Pr18Li8Fe4RuO39) or below.

Pr18Li8Fe5−xMxO39 (M=Ru, Mn, Co) have been studied by neutron diffraction, Mössbauer spectroscopy and magnetometry, allowing the distribution of the different cation species over the octahedral and trigonal-prismatic coordination sites within the structure to be determined. All the compositions studied undergo a transition to a spin-glass-like phase on cooling below ∼5 K.Figure optionsDownload as PowerPoint slide