9 TABLE I: The particle size (d) of the milled samples are determined from the TEM data. The fit parameters (C and θ$_{w}$ ) were obtained using simple Curie-Weiss law (equation 1). The parameters (C$_{eff}$, θ 1 , θ 2 and ξ ) were obtained using equation (2) for different milled samples. It may be mentioned that the present values of C and θ$_{w}$ (K) using temperature range 330 K to 400 K are slightly different from the values C ∼ 0.0176 and θ$_{w}$ ∼ 275 K using temperature range 300 K to 340 K and previously repored [11]. Sample d C (K g Oe/emu) θ$_{w}$ (K) C$_{eff}$ (K g Oe/emu) θ 1 (K) θ 2 (K) ξ (arb. unit) Bulk few µ m 0.196 270 – – – – mh25 65 nm 0.0275 200 0.035(3) 120 ± 4 251 106450 ± 2200 mh61 12 nm 0.0365 100 0.043(2) 33 ± 3 250 53400 ± 520 mh98 16 nm 0.0244 20 0.043(2) -46 ± 4 247 91800 ± 1000 mh146 60 nm 0.0251 -80 0.024(6) -87 ± 2 243 80000 ± 1200 mh200 90 nm 0.0245 -97 0.024(3) -106 ± 3 242 62000 ± 800