title: Layer-preferential substitutions and magnetic properties of pyrrhotite-type Fe7-yMyX8 chalcogenides (X = S, Se; M = Ti, Co).
abstract: A comparative study of four series of pyrrhotite-type chalcogenide compounds Fe(7-y)M(y)X(8) (X = S, Se) with substitution of Ti or Co for iron has been performed by means of x-ray and neutron powder diffraction, and by magnetization measurements. In Fe(7-y)M(y)X(8) compounds having a ferrimagnetic order at y = 0, the substitution of either Ti or Co for iron is observed to result in a monotonous decrease of the magnetic ordering temperature, while the resultant magnetization shows a non-monotonous behavior with a minimum around y = 1.0-1.5 in all the Fe(7-y)M(y)X(8) families except Fe(7-y)Co(y)Se(8). Suppression of a magnetically ordered state with substitutions in Fe(7-y)M(y)X(8) is ascribed to nearly zero values of Ti and Co magnetic moments, while the non-monotonous changes of the resultant magnetization are explained by the compensation of the sublattice magnetizations due to the non-random substitutions in alternating metallic layers. The difference in the cation partitioning observed in Fe(7-y)Ti(y)X(8) and Fe(7-y)Co(y)X(8) is attributed to the difference in the spatial extension of Ti and Co 3d orbitals. High coercive field values (20-24 kOe) observed at low temperatures in the Ti-containing compounds Fe(7-y)Ti(y)X(8) with y ⩾ 3 are suggested to result from the enhancement of Fe orbital moment due to the Ti for Fe substitution.
authors.affiliation: Institute of Metal Physics, Russian Academy of Science, 620990, Ekaterinburg, Russia. Institute of Natural Sciences, Ural Federal University, 620083, Ekaterinburg, Russia.
authors.forename: N V
authors.initials: NV
authors.lastname: Baranov
authors.forename: P N G
authors.initials: PN
authors.lastname: Ibrahim
authors.forename: N V
authors.initials: NV
authors.lastname: Selezneva
authors.forename: A F
authors.initials: AF
authors.lastname: Gubkin
authors.forename: A S
authors.initials: AS
authors.lastname: Volegov
authors.forename: D A
authors.initials: DA
authors.lastname: Shishkin
authors.forename: L
authors.initials: L
authors.lastname: Keller
authors.forename: D
authors.initials: D
authors.lastname: Sheptyakov
authors.forename: E A
authors.initials: EA
authors.lastname: Sherstobitova