MAGNETIC AND ELECTRIC PROPERTIES OF BI(LA)SR(CA)MN2O6

Bi1-xLaxSrMn2O6 and BiSr1-xCaxMn2O6 are prepared by solid state reacti on. They are n-type semiconductors with ferromagnetism at room tempert ure. When Bi is substituted partly by rare earth, a negative magnetore sistance effect is observed in the pellet of Bi1-xLaxSrMn2O6. There ar e semiconductor-metal transitions at 820 K in BiSrMn2O6. The transitio ns are attributed to the magnetic transition at high temperature. The substitution of Ca for Sr makes the transition temperature increase. H owever, when Bi is partly substituted by La, the solid solution does n ot change into metal. (C) 1996 Academic Press, Inc.