Hyperfine interactions, charge compensation mechanisms, and the distribution of tin dopant cations in rare-earth orthochromites RCrO3 (R = Sm, Eu, Gd, Ho)
The reduction in the squared cosine of angle θ of the Cr-O-Cr bond in the Sm-Ho series in samples containing Sn4+ ions in the Cr3+ position in the crystallite bulk is accompanied by a linear increase in hyperfine field HT→0 K at 119Sn nuclei. Upon annealing in H2, tin attains oxidation state +2 occupying the Cr3+ and R3+ positions on the surfaces of particles. Mössbauer measurements in situ at 100 K do not reveal the spin polarization of Sn2+, but this polarization does manifest itself for part of the daughter Sn4+ ions formed when samples come into contact with air.