The Effect of Mechanical Activation on the Synthesis and Properties of Multiferroic Lead Iron Niobate
The present work studies the effect of high-energy mechanical activation using the planetary-centrifugal ball mill AGO-2 and subsequent annealing on the synthesis and magnetic properties of PbFe0.5Nb0.5O3 (PFN). This technique enables one to perform the mechanically activated synthesis of PFN at much shorter time. The results of X-ray phase analysis, electron microscopic studies and transmission Mossbauer 57Fe spectra measurement are presented and discussed. Mossbauer studies show that the temperature of magnetic phase transition in PbFe0.5Nb0.5O3 powders can be changed by mechanical activation and subsequent annealing.
Electron microscopy, X-Ray diffraction and Mossbauer studies of PbFe0.5Nb0.5O3, PbFe0.5Ta0.5O3 and BaFe0.5Nb0.5O3 ceramics sintered from mechanoactivated nanopowders
ABSTRACT The effect of high-energy mechanical activation on magnetic phase transition temperature TM of PbFe0.5Nb0.5O3, PbFe0.5Ta0.5O3, and BaFe0.5Nb0.5O3 perovskites has been studied. Mossbauer studies have shown that TM values in all the perovskites studied can be changed substantially by mechanical activation and subsequent annealing. The increase of TM by 40-50 K, as compared to corresponding single crystals and ceramics sintered from the non-activated powders, was achieved in the mechanoactivated powders of both lead-containing and lead-free perovskites studied.
Investigation of magnetic frustration in A2FeMO6(A Ca, Sr, Ba; M Nb, Ta, Sb) by magnetometry and Mössbauer spectroscopy
Perovskite-related compounds in the series A2FeMO6(A Ca, Sr, Ba; M Nb, Ta, Sb) have been prepared using the standard techniques of solid state chemistry and characterized by X-ray powder diffraction, magnetometry and Mossbauer spectroscopy. All but the 6H hexagonal compound Ba2FeSbO6 adopt cubic or pseudo-cubic crystal structures and show a magnetic susceptibility maximum at ca. 25 K. Field cooled and zero-field cooled susceptibility data show a hysteresis below this maximum. The Mossbauer spectra recorded at 4.2 K comprise a single magnetic hyperfine pattern typical of Fe3+, but with a high degree of line broadening. The spectra show a relaxational (nonBrillouin) collapse above 20 K. The data are described in terms of spin-glass behaviour and the factors controlling the magnetic properties are discussed.