3 Recently, La 0 . 67 Ca 0 . 33 MnO 3 nanoparticles in crystalline and amorphous structural phases have shown many interesting magnetic properties, related to magnetic disorder at core- shell structure of the particles [11]. A proper knowledge of magnetic interactions between core-shell spins would be useful not only to realize the colossal magnetoresistance and inter- grain tunneling of polarized spins, but also relevant to realize the effect of disorder on double exchange ferromagnetism in manganites. In the present work, we demonstrate that the modified magnetism in ferromagnetic La 0 . 67 Ca 0 . 33 MnO 3 nanoparticles is identical to the typical features of ferrimagnetic materials. The evidence of ferrimagnetic signature in La 0 . 67 Ca 0 . 33 MnO 3 nanoparticles is also discussed by comparing the features already observed in ferrimagnetic (Mn 0 . 5 Ru 0 . 5 Co 2 O 4 and MnCr 2 O 4 ) particles. Details of the sample preparation of La 0 . 67 Ca 0 . 33 MnO 3 (perovskite) particles and their characterization have been reported elsewhere [11]. In brief, the polycrystalline bulk La 0 . 67 Ca 0 . 33 MnO 3 sample was prepared by solid state sintering (maximum temperature 1380 $^{0}$C) method. The bulk sample was subjected to mechanical milling in Argon atmo- sphere upto 200 hours using Fritsch Planetary Mono Mill ”Pulverisette 6” to synthesize the material in nanocrystalline and amorphous phase. The structural phase of the samples was confirmed from room temperature XRD spectrum. The XRD spectrum indicated that crystalline nature of the material decreases significantly for the milling time more than 61 hours and amorphous phase dominates in the spectrum for milling time more than 98 hours. Both bulk and milled samples (upto mh98) are in similar crystallographic phase and found to be matching with orthorhombic structure with Pnma space group. The temperature dependence of magnetization under zero field cooled condition was measured using SQUID magnetometer (MPMS-Quantum Design, USA). The temperature dependence of dc mag- netization at 100 Oe in the temperature range 100 K to 400 K was also reproduced using vibrating sample magnetometer (Lakeshore 7404 model). II. EXPERIMENTAL