Correlation of the magnetic and transport properties with polymorphic transitions in bismuth pyrostannate Bi2(Sn1 − x Cr x )2O7

Abstract

The correlation of the electrical, magnetic, and structural properties of Bi 2 (Sn 1 -x Cr x ) 2 O 7 solid solutions has been investigated for two compositions with x = 0.05 and 0.1. The temperatures of structural phase transitions and anomalies of the electrical resistance in the vicinity of these transitions at temperatures in the range 300 K < T < 1000 K have been determined using differential scanning calorimetry. It has been found that the thermoelectric power changes sign upon the polymorphic transition. The paramagnetic Curie temperature and the chromium ion spin have been found from the temperature dependence of the magnetic susceptibility in the range 4 K < T < 1000 K and from the field dependence of the magnetic moment in mag netic fields of up to 6 T.

The effect of cation substitution on conductivity in the region of structural phase transition

“…The compound Bi 2 Sn 2 O 7 is dielectric and the substitution tin ions by 3d metals induces various types of exchange interactions. So, an antiferromagnetic exchange occurs between manganese ions, and at substitution by trivalent chromium, the spins of ions strive to line up ferromagnetically [4]. Replacement of Sn 4+ by Cr 3+ induces the charge ordering, and the interaction between the magnetic and ferroelectric subsystems, ferroelectric properties can be obtained as a result [5][6][7].…”