Effect of Cu doping and oxygen-annealing on the magnetic properties of Nd_(0.5)Sr_(0.5)Mn_(1-x)Cu_xO_(3-δ) (x = 0.0, 0.01, 0.03, 0.05 and 0.10)

摘要

The polycrystalline samples with nominal compositions Nd_(0.5)Sr_(0.5)Mn_(1-x)Cu_xO_3 (x = 0.0, 0.01, 0.03, 0.05 and 0.10) have been synthesized with the aim to study the change in the structural, magnetic and electrical properties due to substitution of Cu for Mn and oxygen-annealing. The temperature dependence magnetization measurement shows a charge ordering transition (T_(co)) at 240 K in Nd_(0.5)Sr_(0.5)Mn0_3 sample. The Neel temperature (T_N) increases with increasing the Cu doping content but changes induced by even 0.1 Cu doping are quite small. As compared to the air sintered samples, higher values of T_n are observed for the oxygen annealed samples. Furthermore, oxygen annealing enhances the magnetization of the samples. It is also found that T_c increases and T_n decreases with increase in the applied magnetic-field. The value of resistivity decreases with the increasing Cu content from x = 0.0 to x = 0.03 and afterwards it increases with increasing value of x up to 0.10 for both air and oxygen sintered samples. It is also found that oxygen annealed samples exhibit higher resistivity than the air sintered samples. In the present paper the results are discussed according to the change of magnetic exchange interaction caused by Cu-doping. It is also found that the amount of Mn~(4+) appears to be the main variable which influences the physical properties.