**2. Experimental details**

The polycrystalline sample La0.67Ca0.18Sr0.15Mn0.98Ni0.02O3 was prepared using the sol–gel method. The sol–gel process is a very well known and proven method to generate homogeneous particles having a great quality and thin material. We have produced the polycrystalline La0.67Ca0.18Sr0.15Mn0.98Ni0.02O3 through sol–gel process. During this method, the basic reagents, *C*6*H*9*La O*6, *H*2*O*, *C*4*H*6*Ca O*4,2*O*, *C*4*H*6*MnO*4, 4*H*2*O* and *NiCl*26*H*2*O* have been weighed using stoichiometric ratios which were dissolved in distilled water under continued stirring. By adding an excess of citric acid, a sol was obtained by slow evaporation from the addition of ethylene glycol, which rendered the solution complex (with a molar ratio of 1:2:2 with regard to the cations: citric acid:ethylene glycol). Subsequently, every reagents have been diluted, and the mixture has been heated up on a hot plate, which gives a gel form. This gel was then dried and calcined for 5 h at 600°C. After, resultant powders have been annealed at 1000°C during 24 h and compressed to form circular pellets. The resulting pellets have been then sintered in air through 1000°C for approximately 10 h. Using X-ray diffraction, the crystalline structure of the studied powder was verified, confirming further that the specimen actually crystallizes into the rhombohedral structure having R3c space group, this was achieved through the use of X-ray diffraction (Siemens D5000 X-ray diffractometer, using monochromatic Cu Kα radiation *λ* = 1.5406 A°).

*Study of the Critical Behavior in La0.67Ca0.18Sr0.15Mn0.98Ni0.02O3 Manganite Oxide DOI: http://dx.doi.org/10.5772/intechopen.105053*

We also measured the magnetic isotherms of the sample over a 0–5 T range, approximately the PM-FM, phase transition, through a vibrating sample magnetometer designed in the laboratory of Louis Neel in Grenoble, for precise extraction of ceramic specimen's critical exponent. Isotherm value was adjusted by means of a demagnetization coefficient *D* that was calculated according to a standardized procedure based on measurement of low field DC magnetization under low temperature (*H* = *H*app � DM).
