Magnetic and charge ordering properties of Bi_(0.2)Ca_(0.8)Mn_(0.9)X_(0.1)O_3 (where X = Ti, Cr, Fe, Co, Ni, Cu)

摘要

Structural, magnetic and transport properties of Bi_(0.2)Ca_(0.8)Mn_(0.9)X_(0.1)O_3 (where X = Ti, Cr, Fe, Co, Ni, Cu) have been investigated. The parent sample Bi_(0.2)Ca_(0.8)MnO_3 (BCMO) exhibits robust charge-ordered antiferrro-magnetic (COAFM) phase with charge ordering temperature (Tco) ~155 K and AFM Neel temperature (T_N) ~105 K. T_(CO) decreases by ~10 K and ~33 K, respectively, in Ni~(2+) and Cu~(2+) doped samples, while it increases by 42 K in Ti~(4+) doped sample. In case of Fe~(3+), Co~(3+) and Cr~(3+) doped samples charge-ordering (CO) completely melts. The paramagnetic (PM) to ferromagnetic (FM) transition temperatures (Tc) of doped samples have lower values as compared to undoped one. In addition, a spin glass (SG) state is observed in all the samples and the magnetic state at T< Tc is akin to a cluster glass (CG) for undoped and Ni, Cu, Ti doped samples formed due to the presence of FM clusters in COAFM matrix. Furthermore, the enhancement in resistivity in all the doped samples with respect to undoped one has been observed. Based on the present study it has been proposed that the disorder induced by doping on the Mn site and magnetic exchange interactions between Mn and doped ions play a key role in explaining magnetic and electrical properties.