Oxydes pour la spintronique

First principle study of the magnetism of Sr2CoMoO6-δ (δ=0, 1/2) double perovskites
Etz C, Stoeffler D, EUROPEAN PHYSICAL JOURNAL B 54 (4) : 429-434 DEC 2006

We investigate the electronic structure of bulk Sr2CoMoO6-δ double perovskites using the ab initio Full Potential Linearized Augmented Plane Wave method in order to study their magnetic properties within the GGA and GGA+U methods. We discuss the relative stability of ferromagnetic (FM) and antiferromagnetic (AFM) orders (i) without and with taking into account the observed tilting of the oxygen octahedra and (ii) by introducing oxygen vacancies. We show that a very good agreement with experimental results – AFM order for δ = 0 and FM order for δ = 1/2 – is obtained only when the tilting of the oxygen tetrahedra is taking into account and when the GGA+U method is used.

Ab initio electronic structure and magnetism in Sr2XMoO6 (X = Fe or Co) double perovskite systems : a GGA and GGA+U comparative study
Stoeffler D, Etz C, JOURNAL OF PHYSICS-CONDENSED MATTER 18 (49) : 11291-11300 DEC 13 2006

Using the full potential linearized augmented plane wave ab initio method, we investigate bulk magnetic properties of Sr2XMoO6 (X = Fe, Co) double perovskites by comparing the results obtained with the generalized gradient approximation (GGA) and GGA+U methods in order to discuss their magnetic configuration in relation with the experiments. We show that both methods lead to significantly different results and that a good agreement with experimental results – antiferromagnetic insulator for X = Co – can be obtained only when the GGA+U method is used. For X = Fe, we exhibit the role played by oxygen vacancies in the stabilization of a negative magnetic moment on the Fe antisite with preserved half-metallicity. We show that such a negative moment can be obtained only when an oxygen vacancy occurs in the direct neighbourhood of the Fe antisite with the GGA+U method.

Diode effect in all-oxide Sr2FeMoO6-based magnetic tunnel junctions
Fix T, Stoeffler D, Henry Y, et al., JOURNAL OF APPLIED PHYSICS 99 (8) : Art. No. 08J107 APR 15 2006

Ab initio study of the electronic structure of Sr2FeMoO6 double perovskites presenting oxygen vacancies or/and antisite imperfections
Stoeffler D, Colis S, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 126 (2-3) : 133-138 JAN 25 2006

Oxygen vacancies or/and antisite imperfections in Sr2FeMoO6 double perovskites : an ab initio investigation
Stoeffler D, Colis S, JOURNAL OF PHYSICS-CONDENSED MATTER 17 (41) : 6415-6424 OCT 19 2005

We report on electronic band structure calculations, using the ab initio full potential linearized augmented plane wave (FLAPW) method, for Sr2FeMoO6 (SFMO) double perovskites presenting antisite defects or/and oxygen vacancies. We exhibit that the half-metallic character is preserved for SFMO containing only nearly isolated oxygen vacancies, indicating that the control of oxygen content in such compounds is less critical for the transport properties than the control of the antisite defects. We show that the total magnetic moment is much more reduced for structures with oxygen vacancies (approximately 2 µB per vacancy) than for structures without. We also investigate the stability of an antiparallel (AP) magnetic moment on Fe antisites and we show that these solutions are highly unstable relative to the parallel (P) solution, even if the presence of O vacancies reduces the difference between P and AP solutions.

Structural defects in Sr2FeMoO6 double perovskite : Experimental versus theoretical approach
Colis S, Stoeffler D, Meny C, et al., JOURNAL OF APPLIED PHYSICS 98 (3) : Art. No. 033905 AUG 1 2005

Effects of strain relaxation on the electronic properties of epitaxial Sr2FeMoO6 grown by pulsed laser deposition on SrTiO3 (001)
Fix T, Stoeffler D, Colis S, et al., JOURNAL OF APPLIED PHYSICS 98 (2) : Art. No. 023712 JUL 15 2005

Ab initio investigation of the electronic structure of Sr2FeMoO6 double perovskites presenting imperfections
Stoeffler D, Colis S, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 290 : 400-404 Part 1 Sp. Iss. SI APR 2005