Determination of Mn valence from X-ray absorption near edge structure and study of magnetic behavior in hole-doped (Nd1-xCax)MnO3 system

The Mn valence in (Nd1-xCax)MnO3 (x = 0-0.5) has been successfully determined using Mn 2(p)-edge X-ray absorption near edge structure spectra. Moreover, we have measured the magnetic properties across the series (Nd1-xCax)MnO3; the results show that the perovskite NdMnO3 is an antiferromagnet with two Neel temperatures (T-N) Of 14 and 60 K, respectively. By replacement of Nd3+ with Ca2+, the mixed compounds (Nd1-xCax)MnO3 became ferromagnetic with a Curie temperature of around 130 K (T-C) for x in the range 0.1-0.3. Furthermore, two weak antiferromagnetic transitions with T-N's Of around 30 and 75 K, respectively, embedded in the matrix of the ferromagnet have also been discovered in the range x 0.2-0.3. For x greater than or equal to 0.4, the samples change to antiferromagnetic with T-N's of around 30 K together with a weak broad ferromagnetic transition with T-C's of around 130 K. Tt is also important to note that the charge-ordering-induced antiferromagnetic transition at the temperature (T-CO) 250 Ei was observed in the samples of x = 0.4 and 0.5. (C) 1996 Academic Press, Inc.