CRITICAL BEHAVIOR IN Lao.7Sro.3Mno.9sCuo.02O3 COMPOUND

Tóm tắt

The magnetic data o f Lao.7Sr().3Mn()^Cuo.()20j in the ferro-paramagnetic phase transition region has been analyzed using the Modified Arrott plots (MAP), the Kouvel-Fisher and the scaling hypothesis methods. The obtained data is compared to 4 theoretical models: Mean field, 3D Heisenberg, 3D Ising and Tritical mean field. The results suggest that the magnetic interaction in the sample is corresponding to the 3D Ising model. The n value (which relates to the magnetic order) conducted by law ASmax = a (ụ ồH Ỵ is 0.641(8). This value is different from 0.556(5) derived from critical exponents o f/3 and Ỵ extracted from fitting values o f spontaneous magnetisation and initial sitsceptibility to Kouvel-Fisher law. A low value of entropy is changed but the relative cooling power is improved.
Keywords: Magnetocaloric, critical exponents, manganites, perovskite.