content_image/348920.jpg
## III. EXPERIMENTAL RESULTS 

Details of the temperature and field dependence of dc magnetization have been reported elsewhere [11]. In summary, the paramagnetic to ferromagnetic Curie temperature (T$_{C}$) for bulk (LCMN) sample is nearly 281 K and T$_{C}$ decreases to 262 K, 250 K, 238 K, 225 K and 212 K for mechanical milled mh25(nanocrystalline, particle size ∼ 65 nm), mh61 (nanocrystalline, particle size ∼ 12 nm), mh98 (nanocrystalline+amorphous, particle size ∼ 16 nm), mh146 (amorphous, particle size ∼ 60 nm) and mh200 (amorphous, particle size ∼ 90 nm) samples. At the same time, the long ranged ferromagnetic order (spontaneous magnetization ∼ 3.6 µ$_{B}$ ) of bulk LCMN sample decreases to 2.17, 0.87, 0.35, 0.17, 0.10 (in µ$_{B}$ ) unit) for mh25, mh61, mh98, mh146 and mh200 samples, respectively. These are some typical features of the magnetic disorder effect in ferromagnetic materials. In the present paper, we would like to show some specific magnetic features of the samples based on magnetization data at (higher temperature) paramagnetic regime. In Fig. 1, the dc magnetic susceptibility ( χ$_{dc}$ = M/H) of bulk LCMN sample sharply increases above the magnetization peak temperature T$_{p}$ ∼ 260 K. On the other hand, magnitude of susceptibility, as well as sharp increase of magnetization below the respective T$_{C}$ systematically decreases for mh25, mh98 and mh200 samples. The decrease of the χ (T) variation in milled samples reflects the increasing magnetic disorder in the ferromagnetic material and realized in the previous work [11]. Interestingly, a typical ferrimagnetic sample, e.g., Mn 0 . 5 Ru 0 . 5 Co 2 O 4 (RuMn) spinel oxide in the inset of Fig. 1, also exhibits the similar χ$_{dc}$ (T) behaviour above its magnetization peak temperature T$_{p}$ ∼ 100 K. This means only the shape of χ$_{dc}$ (T) curve in the paramagnetic state can not determine the nature of magnetic order in the samples, whether ferromagnet or ferrimagnet. The nature of magnetic order can be confirmed in convincing manner from the temperature dependence of the inverse of magnetic susceptibility in the paramagnetic state. For this purpose, we extended the dc magnetization measurement up to 400 K. First, we confirm the difference of the temperature dependence of the inverse of susceptibility curve in paramagnetic regime between bulk LCMN (ferromagnetic) and RuMn (ferrimagnetic) samples. Fig. 2 shows that the inverse of dc susceptibility ( χ − 1 dc = H/M) data for bulk LCMN sample at high temperatures (T ≥ 300 K) are fitted with a simple Curie-Weiss law: 

<img src='content_image/348920.jpg'>

