Effects of oxygen deficit, Sr, Ti and Cr substitution on the antiferro-ferromagnet transition in Nd0.6Ca0.4MnO3

We have investigated phase transitions in Nd0.6Ca0.4-xSrx(Mn1-yMy)O3-y (M = Cr, Ti) by measurement of magnetization and electrical transport in magnet ic fields up to 12 T. It is shown that oxygen deficit up to y = 0.03, Sr do ping up to x = 0.05 and Cr doping up to y = 0.03 lead to strong decrease of magnetic field which induces antiferro-ferromagnet (A-F) transition. Sampl es with chromium content above y = 0.03 and Sr-content above x = 0.1 are fe rromagnets whereas in the samples with large oxygen deficit an antiferromag netic structure is stabilized. The magnetization measurements indicate the ferromagnetic coupling between manganese and chromium ions. (C) 1999 Elsevi er Science B.V. All rights reserved.