Lattice effects on the magnetic and transport properties in La(1.4)Sr(1.6-x)A(x)Mn(2)O(7) (A = Ca, Ba)

The structural and physical properties of the Ruddlesden-Popper phases La(1 .4)Sr(1.6-x)A(x)Mn(2)O(7) (A = Ca, Ba) were studied. Single phase compounds were obtained up to x = 0.4 for Ca and x = 0.3 for Ba, respectively. Their magnetic and transport behavior is largely dependent upon the size of the A cations. By comparison with the magnetic and transport properties of the parent compound La1.4Sr1.6Mn2O7, the samples substituted by Ca and Ba exhib it reduced magnetic moments and conductivity. There is also a growing spin- glass like character with substitution. These can be explained by suppresse d ferromagnetic double exchange interactions that result from local distort ions by the size mismatch among La, Sr, and Ca/Ba. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.