DC magnetization studies of nano- and micro-particles of bilayered   manganite LaSr2Mn2O7
  Systematic studies of magnetic properties of LaSr2Mn2O7 as a function of crystalline grain size provide information on how the crystalline grain size affects the magnetic and charge ordering in this compound. The half-doped bi-layered manganite LaSr2Mn2O7 (x=0.5) in its bulk form has CE-type antiferromagnetic (CE-AFM) charge ordering phase transition. In this work, we have prepared LaSr2Mn2O7 ceramic samples using Pechini sol-gel method to produce different grain sizes and the effect of crystalline grain sizes between 150 200 to 1000 nm on magnetic properties results obtained by the SQUID magnetometer have been investigated. The DC magnetization (DCM) measurements for all samples indicate that the crystalline grain size has no considerable effect on TCO. Just the temperature of charge ordering peak becomes sharper, and susceptibility measurement in the zero field cooling (ZFC) and filed cooling (FC) increases as the grain sizes becomes systematically smaller. The results obtained from magnetic hysteresis curves confirm the anti-ferromagnetic phase formation as a ground state and Arrott plots obtained manifest the existence of first and second order magnetic phase transition in all samples. In addition, in sample with a grain size of 150 200 nm, enhancement of the magnetic properties, which is accompanied with the formation of FM phase on the surface of grain or particle, is observed. 
M. E. Ehsani, M.E. Ghazi, P. Kameli, F.S. Razavi
cond-mat.mtrl-sci cond-mat.str-el cond-mat.supr-con