A NEUTRON-DIFFRACTION STUDY OF THE PR(1-X)(3-2X)(3+)MN(2X)(4+)O(3) (A=K, NA) PEROVSKITES()A(X)(+)MN(1)

The mixed-valence manganites Pr1-x3+Kx+Mn2x4+O3 and Pr1-x3+Nax+Mn1-2x3 +Mn2x4+O3 have been prepared up to maximum content of 30% Mn4+ and 40% Mn4+ (x = 0.15 and 0.20), respectively and investigated by neutron di ffraction. The structural determination of these types of perovskites has been performed within the space group Pbnm and complete structure parameters and data on magnetic arrangements were given. As to the cry stal structure and magnetic ordering, the potassium and natrium system s behave similarly to manganites with divalent substitutions and the s ame Mn4+ content. In particular, the concentration transition from the antiferromagnetic ordering for PrMnO3 to the ferromagnetic one for 20 % of(x = 0.10 for the present systems) involves true canted arrangemen ts. This supports the concept of the double-exchange interactions betw een the disordered Mn3+ and Mn4+ pairs. (C) 1998 Elsevier Science B.V. All rights reserved.