Magnetotransport properties of the Sm-0.56(Sr0.44-xMex)MnO3 (Me = Ba, Ca, Cd) perovskites

The magnetization, magnetoresistance and elastic properties of Sm-0.56(Sr0. 44-xMex)MnO3 (Me = Pa, Cd, Ca) have been investigated. It is established th at Sm0.56Sr0.44MnO3 exhibits a metamagnetic behaviour as well as anomalous elastic properties in a wide range of temperatures above the Curie point T- C = 134 K. Small additions of Ba Cd and Ca ions lead to (i) an inhomogenous magnetic state appearance and (ii) an irreversible metamagnetic behaviour below the Curie point. Further increase of Bg Cd or Ca destroys the long-ra nge ferromagnetic order giving rise to a spin-glass-like behaviour. Strongl y reduced Sm0.56Ba0.44MnO2.68 is a weak ferromagnet with T-N = 137 K. It is supposed that short-range charge ordering occurs in these compounds. The m etamagnetic behaviour is associated with a concurrence of positive and nega tive superexchange interactions in the Ising antiferromagnet.