Evidence of Ferrimagnetism in Ferromagnetic La$_{0}$$_{.}$$_{67}$Ca$_{0}$$_{.}$$_{33}$MnO$_{3}$ nanoparticle arXiv:1002.4574v2 [cond-mat.mes-hall] 25 Feb 2010 R.N. Bhowmik ∗ Department of Physics,Pondicherry University, R.V. Nagar, Kalapet, Pondicherry-605014, India The present report is dedicated to show that ferromagnetic La 0 . 67 Ca 0 . 33 MnO 3 (LCMN) particles can be better described in the framework of ferrimagnetic model. To confirm the ferrimagnetic signature in ferromagnetic LCMN particles, the tem- perature dependence of the inverse of magnetic susceptibility in the paramagnetic state of the samples was taken as a tool of data analysis. The observed ferrimag- netism is understood as an effect of of the core-shell spin structure in LCMN particles. Key Words: A. Ferromagnetic nanoparticle; B. Mechanical Milling; C. Ferrimag- netism; D. Core-shell spin structure PACS:75.47.Lx,75.30.Cr,75.50.-y,75.50.Gg,75.50.Tt Magnetic nanomaterials are continued to be at the center of current research interests due to their huge technological applications and incomplete undestanding of many discov- ered phenomena. For example, superparamagnetic blocking of magnetic moments below the conventional paramagnetic to ferromagnetic transition temperature (T$_{C}$), appearance of unconventional spin glass behaviour at lower temperatures, decrease of effective magnetic moment of the material, exchange bias effect, quantum tunnelling of magnetization, and low field magnetoresistance have been observed when the particle size of ferromagnetic materi- als decreases into nanosize dimension (below 100 nm)[1, 2]. Various mechanisms have been introduced in literature to describe the magnetic features of nanoparticles, e.g., core-shell I. INTRODUCTION ∗ E-mail address for correspondence: rnbhowmik.phy@pondiuni.edu.in