Perovskites of the LnV1-XFeXO3 type (with Ln = La – Er, Y) were synthesized by rapid solidification and structurally and magnetically characterized by X-ray diffraction, transmission electron microscopy, magnetometry and Mössbauer spectroscopy (57Fe, 151Eu and 155Gd). These solid solutions crystallized with the Pbnm symmetry, with the iron and vanadium cations randomly distributed in the transition metal octahedral sites. Heat treatments at 1100ºC revealed that these distorted orthorhombic compounds are metastable what may explain why they had not been synthesized and effectively characterized before, in spite of the extensive investigations earlier carried out on the end compounds, i.e., the LnFeO3 orthoferrites and LnVO3 orthovanadates. For X = 0.50, the lattice parameters follow linearly the lanthanide contraction and similar temperature dependences for magnetization were revealed by groups of two or three lanthanides, though all of them transiting near RT between ordered and not-ordered states. Also depending on the lanthanide composing the X = 0.50 perovskite, iron is present with two valences (i.e., Fe3+ and Fe2+) in these compounds. At 85K, the ferric cation occupies two magnetically different sites, indicating that a phase transition takes place when lowering the temperature. It is suggested that this is an orbital transition of the kind frequently observed for some orthovanadates. Mössbauer spectroscopy also showed that the presence of iron, sharing the transition cation sites with vanadium in the perovskite structure, inhibits or suppresses the R.E. magnetic ordering usually observed at liquid helium temperatures for the LnVO3 perovskites.
Perovskites of the LnV1-XFeXO3 type (with Ln = La – Er, Y) were synthesized by rapid solidification and structurally and magnetically characterized by X-ray diffraction, transmission electron microscopy, magnetometry and Mössbauer spectroscopy (57Fe, 151Eu and 155Gd). These solid solutions crystallized with the Pbnm symmetry, with the iron and vanadium cations randomly distributed in the transition metal octahedral sites. Heat treatments at 1100ºC revealed that these distorted orthorhombic compounds are metastable what may explain why they had not been synthesized and effectively characterized before, in spite of the extensive investigations earlier carried out on the end compounds, i.e., the LnFeO3 orthoferrites and LnVO3 orthovanadates. For X = 0.50, the lattice parameters follow linearly the lanthanide contraction and similar temperature dependences for magnetization were revealed by groups of two or three lanthanides, though all of them transiting near RT between ordered and not-ordered states. Also depending on the lanthanide composing the X = 0.50 perovskite, iron is present with two valences (i.e., Fe3+ and Fe2+) in these compounds. At 85K, the ferric cation occupies two magnetically different sites, indicating that a phase transition takes place when lowering the temperature. It is suggested that this is an orbital transition of the kind frequently observed for some orthovanadates. Mössbauer spectroscopy also showed that the presence of iron, sharing the transition cation sites with vanadium in the perovskite structure, inhibits or suppresses the R.E. magnetic ordering usually observed at liquid helium temperatures for the LnVO3 perovskites.
1-XFeXO3 type (with Ln = La – Er, Y) were synthesized by rapid solidification and structurally and magnetically characterized by X-ray diffraction, transmission electron microscopy, magnetometry and Mössbauer spectroscopy (57Fe, 151Eu and 155Gd). These solid solutions crystallized with the Pbnm symmetry, with the iron and vanadium cations randomly distributed in the transition metal octahedral sites. Heat treatments at 1100ºC revealed that these distorted orthorhombic compounds are metastable what may explain why they had not been synthesized and effectively characterized before, in spite of the extensive investigations earlier carried out on the end compounds, i.e., the LnFeO3 orthoferrites and LnVO3 orthovanadates. For X = 0.50, the lattice parameters follow linearly the lanthanide contraction and similar temperature dependences for magnetization were revealed by groups of two or three lanthanides, though all of them transiting near RT between ordered and not-ordered states. Also depending on the lanthanide composing the X = 0.50 perovskite, iron is present with two valences (i.e., Fe3+ and Fe2+) in these compounds. At 85K, the ferric cation occupies two magnetically different sites, indicating that a phase transition takes place when lowering the temperature. It is suggested that this is an orbital transition of the kind frequently observed for some orthovanadates. Mössbauer spectroscopy also showed that the presence of iron, sharing the transition cation sites with vanadium in the perovskite structure, inhibits or suppresses the R.E. magnetic ordering usually observed at liquid helium temperatures for the LnVO3 perovskites.