Magnetostriction and thermal expansion of BaPbyBi1-yO3 and Ba1-xKxBiO3 at low temperatures

The effect of magnetic field influence on the thermal expansion anomaly (ne gativity) was observed for Ba1 - xKxBiO3, La2 - xSrxCuO4 and BaPbyBi1 - yO3 systems. With growing magnetic field H the temperature T* of thermal expan sion Delta L/L minimum decreases (L - sample dimension). For BaPbyBi1 - yO3 samples it was revealed the influence of H on relative change of Delta L/L measured through the magnetostriction curves both in superconducting and n ormal metal phases. The observed effect is explained by the influence of th e superstructure ordering in the oxygen sublattice supplementing the orderi ng in metal (Bi or Cu) sublattice. (C) 2000 Elsevier Science B.V. All right s reserved.