Curie-temperature enhancement of electron-dopedSr2FeMoO6perovskites studied by photoemission spectroscopy

Abstract

We report here on the electronic structure of electron-doped half-metallic ferromagnetic perovskites such Sr2−xLaxFeMoO6 (x=0-0.6) as obtained from high-resolved valence-band photoemission spectroscopy (PES). By comparing the PES spectra with band structure calculations, a distinctive peak at the Fermi level (EF ) with predominantly (Fe+Mo) t ↓ 2g character has been evidenced for all samples, irrespectively of the x values investigated. Moreover, we show that the electron doping due to the La substitution provides selectively delocalized carriers to the t ↓ 2g metallic spin channel. Consequently, a gradual rising of the density of states at the EF has been observed as a function of the La doping. By changing the incoming photon energy we have shown that electron doping mainly rises the density of states of Mo parentage. These findings provide fundamental clues for understanding the origin of ferromagnetism in these oxides and shall be of relevance for tailoring oxides having still higher TC .

La-induced changes in the magnetic and electronic properties ofSr2−xLaxFeMoO6

“…Previous studies have shown that electronic doping leads to an increase in the Curie temperature, 7,8 and photoemission spectroscopy data have been interpreted in terms of an increasing density of states at the Fermi level. 17 This has lead to the suggestion that the ferromagnetic state is mediated by the itinerant carriers via Ruderman-Kittel-KasauyaYosida ͑RKKY͒ coupling similar to that proposed to explain the ferromagnetic order in the dilute ferromagnetic semiconductors. 17 In the case of the dilute ferromagnetic semiconductors, it was shown that the Curie temperature increases with an increasing density of states at the Fermi level until a critical concentration beyond which the Curie temperature decreases.…”

“…17 This has lead to the suggestion that the ferromagnetic state is mediated by the itinerant carriers via Ruderman-Kittel-KasauyaYosida ͑RKKY͒ coupling similar to that proposed to explain the ferromagnetic order in the dilute ferromagnetic semiconductors. 17 In the case of the dilute ferromagnetic semiconductors, it was shown that the Curie temperature increases with an increasing density of states at the Fermi level until a critical concentration beyond which the Curie temperature decreases. 18 There is a clear need for further studies of electronic doping in SFMO.…”

Cerámicas magnetorresistivas. Progresos recientes: desde el entendimiento básico a las aplicaciones

“…This is just what one should expect from carrier injection into the antibonding Fe-O-Mo orbitals [23,24]. Recent photoemission experiments have also confirmed that the density of states at the Fermi level increases with the La content [25]. Naturally, for the operation of these materials as ferromagnetic electrodes, the magnetization should also be large.…”

Potassium doping effects on the structure and magnetic properties of Sr2FeMoO6

“…When two transition metals occupancy at different sites in the unit cell, they may transfer charges due to the doping. The substitution of trivalent La ions for the divalent Sr ions induces electron doping and these doping electrons inject into Mo orbit [17]. Our previous work also has demonstrated that the doping electrons reduce the valence state of Mo [18].…”