The Nd-Mn exchange interaction, low temperature specific heat and magnetism of Nd2/3Ca1/3MnO3

The low temperature specific heat and magnetic characteristics of Nd2/3Ca1/3MnO3 perovskite are studied in a wide range of magnetic fields (up to 9 T). Temperature dependent specific heat data show a broadened Schottky-like anomaly below 20 K caused by splitting of the Nd3+ ions ground-state doublet in the effective molecular field H-ex determined by exchange interaction between Nd and Mn spin systems supplemented by an applied external magnetic field. Existence of the splitting at zero magnetic field and expressed field dependence is the evidence of a strong exchange coupling between Nd and Mn magnetic subsystems. The Nd-ions magnetic ordering leads to an additional contribution to the magnetic moment of the system below 30 K, producing anomalies of the magnetic loss and field-cooled and zero-field-cooled magnetizations. The observed broadened Schottky-like anomalies are fitted for each applied magnetic field by the sum of three Schottky functions. Applied magnetic field extends the anomaly region and shifts it to higher temperatures. Splitting of the higher crystal field Kramers doublets gives an additional contribution to the heat capacity in magnetic fields. The ground state doublet g-factors g(parallel to) and g(perpendicular to) were estimated to be 3.4 and 2.2, respectively, and H-ex was estimated to be 9 T. The Nd3+ ions magnetic moment estimated from the magnetization data agrees with the value obtained from the specific heat data. (C) 2011 Elsevier B.V. All rights reserved.