Etude ab-inition des propriétés physiques des nouveaux matériaux ternaires et quaternaires

Abstract

First-principles total energy calculations were performed to study the stability of Rh2TMSn (TM=Cr, Mn, and Fe) toward different magnetic ordering, ferromagnetic (FM), antiferromagnetic type I (AFM-I), and antiferromagnetic type II (AFMII). We studied the effects of electron correlation on the magnetic stability of the compounds in both cubic and tetragonal structures using density functional theory (DFT) within the generalized gradient approximation (GGA) and GGA+U. The results show that the electron correlation has an important role in determining the magnetic stability of the compounds. The magnetic stability obtained from GGA+U agrees well with the available experimental results. The thermodynamic stability of the three compounds shows that all the compounds are stable in both cubic and tetragonal structures. Using the energy difference method, we were able to calculate the exchange interactions and estimate the Curie temperature of the Rh2MnSn a compound in the cubic structure. For the study of the Heusler RhCoTMSn quaternary alloy (TM = Cr, Mn and Fe) we have substituted an Rh atom of the full-Heusler compound Rh2TMSn by the Co atom. we have presented a theoretical study of structural and magnetic properties of Rh CoTMZ (TM = Cr, Mn and Z=Sn, Sb) compounds. This study is conducted by FP-LAPW (Full Potential linearized Augmented Planes waves) method, in the frame-work of the density functional theory (DFT), which is implemented in the Wien2k calculation code. For the exchange and correlation potential, we have used GGA, LDA, GGA_mbj and LDA_mbj. First, we have studied the chemical stability of the four compounds in the cubic structure for the three types (I ,II and III). The optimized lattice parameters, bulk moduli and magnetic moments for the most stable type are calculated by the two approaches GGA and LDA. We have also studied the band structure and the density of state in order to know the value and the nature of the gap and to know how to classify them according to their electronic behavior using LDA_mbj approach. Keywords First-principles calculations · full Heusler alloys · magnetic stability · DFT · electronic properties · Wien2k