Crystal structure, phase transitions and magnetic properties of pyrrhotite-type compounds Fe7−xTixS8

Crystal Structure and Magnetic Properties of Pyrrhotite-Type Compounds Fe7-yVyS8

“…2a shows the concentration dependence of the magnetization M 50 measured in a field of 50 kOe at temperature 2 K on the Fe 7¡y V y S 8 samples. The non-monotonous behaviour of the magnetization was also observed in the Fe 7¡y Ti y S 8 system, which was explained by the ferrimagnetic ordering of the Fe magnetic moments and by non-random substitutions in the cation layers [3,4] since the statistical distribution of substituting atoms should result in the monotonous reduction of the resultant magnetization. For Fe 7¡y Ti y S 8 , the non-random Ti for Fe substitution in alternating cationic layers was derived from neutron diffraction data [4].…”

“…1). As in the case of the Ti for Fe substitution [3,4], the replacement of Fe by V up to y 1 significantly reduces the magnetization, while further growth of the V content results in a non-monotonous change of the magnetization. Fig.…”

“…According to X-ray diffraction all the synthesized samples Fe 7¡y V y S 8 (0 ¤ y ¤ 7) have layered superstructures of the NiAs-type, while in the case of Ti for Fe substitution, the single phase Fe 7¡y Ti y S 8 samples were obtained only at y ¤ 4 [3]. The changes in the crystal structure in Fe 7¡y V y S 8 with substitution can be characterized by the lattice parameters a 0 and c 0 of the NiAs fundamental unit cell.…”

“…For Fe 7¡y Ti y S 8 , the non-random Ti for Fe substitution in alternating cationic layers was derived from neutron diffraction data [4]. The presence of a minimum of the resultant magnetization at y 1.5 in Fe 7¡y V y S 8 may be associated with the compensation of the sublattice magnetizations, as in Fe 7¡y Ti y S 8 [3,4]. However, unlike the The magnetic state of the V-substituted compounds Fe 7¡y V y S 8 with y 5 seems to be non-homogeneous.…”

“…The presence of vacancies in every second Fe layer leads to incomplete compensation of magnetic moments and to a ferrimagnetic order which enters below the Neel temperature of about 590 K [1,2]. The magnetic properties of Fe 7 X 8 are strongly influenced by substitutions in both the Fe [3,4] and chalcogen sublattices [5]. The replacement of iron in Fe 7¡y M y X 8 (X = S, Se) by other 3d metal (M = Ti, Co) atoms in cation layers is found to be non-random and dramatically affects the magnetic behavior [4].…”