Moessbauer Study of (Ca,Sr)RuO3 Doped with 57Fe

2% of 57Fe doped in Ca1-xSrxRuO3 materials ( x ranging from 0 to 1) were prepared by a sol-gel method. The influence of the Sr/Ca ratio on the structural and magnetic properties of ruthenates was investigated by XRD and Moessbauer spectroscopy (15 - 300 K). The refined lattice parameters indicate an expansion of the unit cell volume with Sr and a transition of the crystal symmetry from orthorhombic for x < 0.4 to tetragonal for higher Sr content. This transition is also manifested in the 57Fe Moessbauer spectra through the change of: (a) the quadrupole splitting parameter (∼ 0.1 mm/s for x=0 and ∼0 or slightly negative for x ≥ 0.4 samples). (b) The isomer shift (c) the magnetic hyperfine parameters (Heff), and (d) the magnetic transition temperature, which increase with x. The temperature dependence of Heff is significantly different for the CaRu0.9857Fe0.02O3 as compared to samples with x = 0.6, 0.8 and 1. In the latter materials, Moessbauer spectra at low temperatures show a much wider distribution in Heff In particular, the field maximum probability decreases progressively with T, whereas for the x=0 material, it remains almost constant. Such behavior is closely related with the literature data on a spin glass ordering of Ca1-xSrxRuO3 with x < 0.2 and a ferromagnetic behavior for the rich Sr samples