Raising the Curie temperature in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">FeMoO</mml:mi></mml:mrow><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>double perovskites by electron doping

Navarro, J.; Frontera, C.; Balcells, Ll.; Martı́nez, B.; Fontcuberta, J.

doi:10.1103/physrevb.64.092411

Cited by 251 publications

(228 citation statements)

References 12 publications

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“…An alternative way to enhance T c is to add mobile electrons using La doping, which, however, has been shown to lead to considerable increase in AS disorder [15]. In principle, compensated doping as proposed here should introduce less AS disorder [21].…”

Section: Fig 2: (A) Magnetization Of the Core Spins Ms(t ) And Of Thmentioning

confidence: 99%

Theory of Half-Metallic Ferrimagnetism in Double Perovskites

et al. 2011

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We present a comprehensive theory of the temperature-and disorder-dependence of half-metallic ferrimagnetism in the double perovskite Sr2FeMoO6 (SFMO) with Tc above room temperature. We show that the magnetization M (T ) and conduction electron polarization P (T ) are both proportional to the magnetization MS(T ) of localized Fe spins. We derive and validate an effective spin Hamiltonian, amenable to large-scale three-dimensional simulations. We show how M (T ) and Tc are affected by disorder, ubiquitous in these materials. We suggest a way to enhance Tc in SFMO without sacrificing polarization. Double perovskites (DPs) A 2 BB ′ O 6 are an important family of complex oxides, derived from the simple ABO 3 perovskite structure by a three-dimensional (3D) checkerboard ordering of B and B ′ ions. One of the best studied examples is Sr 2 FeMoO 6 (SFMO), a half-metallic ferrimagnet with T c ≃ 420K, well above room temperature [1][2][3]. Clearly SFMO, and other DPs, can have enormous technological impact if their stoichiometry and ordering can be controlled.From a theoretical point of view, we argue that DPs are simple systems for understanding metallic ferromagnetism, despite their apparent complexity. First, in contrast to iron, there is a clear separation of the localized (B) and itinerant degrees of freedom (coming from B ′ ) in the DPs. Second, in contrast to the manganites, DPs have neither Jahn-Teller distortions nor competing superexchange, given the large distance between B-sites. Third, in contrast to dilute magnetic semiconductors, disorder is not an essential aspect of the theoretical problem. Important early theoretical work on halfmetallic DPs includes T =0 electronic structure calculations [3], and model Hamiltonians analyzed using various mean-field theories [4-6] and two-dimensional (2D) simulations [7].In this Letter, we present a comprehensive theory that gives insight into the temperature-and disorderdependence of the magnetic properties of metallic DPs. We make detailed comparisons with and predictions for SFMO. Our main results are: (1) We show that both the total magnetization M (T ) and the conduction electron polarization P (T ) at E f are proportional to the magnetization M S (T ) of localized Fe spins. This result is significant because, while M (T ) is easy to measure, it is P (T ) that is of crucial importance for spintronic applications.(2) Our main theoretical advance is the derivation and validation of an effective classical spin Hamiltonian H eff [see eq. (2)] for DPs, which differs from both the Heisenberg and Anderson-Hasegawa models [8]. We show that H eff describes the full T -dependence of the magnetization M S (T ), and hence that of M (T ) and P (T ). (3) We present the results of simulations of H eff on large 3D lattices, including disorder effects, thus going beyond all previous theoretical calculations on SFMO. (4) We compute M (T ) and T c , using microscopic bandstructure parameters as input, and see how these are affected by deviations from stoichiometry and by anti-site (A...

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Section: Fig 2: (A) Magnetization Of the Core Spins Ms(t ) And Of Thmentioning

confidence: 99%

Theory of Half-Metallic Ferrimagnetism in Double Perovskites

et al. 2011

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“…To avoid possible complications rising from a structural phase transition and anti-site effects in heavily doped region 15 and to probe only the electronic effects due to La substitution, we concentrate on a lightly-doped region.…”

Section: Introductionmentioning

confidence: 99%

Unusual electron-doping effects inSr2−xLaxFeMoO6
Saitoh
¹
,
Nakatake
²
,
Nakajima
³

et al. 2005
Phys. Rev. B
19
2
13
0
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We have investigated the electronic structure of electron-doped Sr2−xLaxFeMoO6 (x=0.0 and 0.2) by photoemission spectroscopy and band-structure calculations within the local-density approximation+U (LDA+U ) scheme. A characteristic double-peak feature near the Fermi level (EF) has been observed in the valence-band photoemission spectra of both x=0.0 and 0.2 samples. A photon-energy dependence of the spectra in the Mo 4d Cooper minimum region compared with the band-structure calculations has shown that the first peak crossing EF consists of the (Fe+Mo) t 2g↓ states (feature A) and the second peak well below EF is dominated by the Fe e g↑ states (feature B). Upon La substitution, the feature A moves away from EF by ∼50 meV which is smaller than the prediction of our band theory, 112 meV. In addition, an intensity enhancement of both A and B has been observed, although B is not crossing EF. Those two facts are apparently incompatible with the simple rigid-band shift due to electron doping. We point out that such phenomena can be understood in terms of the strong Hund's rule energy stabilization in the 3d 5 configuration at the Fe sites in this compound. From an observed band-narrowing, we have also deduced a mass enhancement of ∼2.5 with respect to the band theory, in good agreement with a specific heat measurement.

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“…2 we show the density of states for the doping Sr 2−y La y FeMoO 6 system, here the number of carriers increases by replacing divalent Sr 2+ by trivalent La 3+ as n = 1 + y [9]. We keep ∆ 0 = 2w/3 as in pure Sr 2 FeMO 6 and vary only n(y).…”

Section: Resultsmentioning

confidence: 99%

“…Experimental results [9] have obtained an important increment of the Curie temperature, reaching 490 K for SrLaFeMoO 6 (y = 1). The number of electrons per f.u.…”

Section: Introductionmentioning

confidence: 99%

“…Increasing the number of conduction electrons in SFMO by substitution of divalent Sr 2+ by trivalent La 3+ ions in Sr 2−y La y FeMoO 6 (SLFMO) seems to be a good mechanism to increases the Curie temperature (T C ) [8,9] because the increased number of electrons reinforces the ferromagnetic interactions between the Fe ions. However, this increase of T C cannot be accounted for by just increasing the carrier density, it has been suggested [4] that correlations within the conduction band could play a crucial role, giving rise by itself to a ferromagnetic instability.…”

Section: Introductionmentioning

confidence: 99%

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Increase of Curie temperature with La doping in the double perovskite Sr2-LayFeMoO6 within an electronic correlation approach

et al. 2018

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The double perovskite compound Sr2FeMoO6 has a half-metallic ferromagnetic character and a high Curie temperature (420 K). Fe-Mo usually present some degree of disorder in either Fe or Mo ions, it is therefore fundamental to understand the role of electronic and structural parameters controlling the half-metallic character together with a Curie temperature as high as possible. We replaced divalent Sr 2+ by trivalent La 3+ ions in Sr 2 FeMoO 6 system to observe the Curie temperature behavior. We present an electronic approach using the Green's functions and the renormalization perturbation expansion method, with localized Fe-spins and conduction Mo-electrons interacting with the local spins via a double-exchange-type mechanism. We also include the electronic correlations among the conduction electrons within a mean-field approximation. Our results show the density of states and the Curie temperature behavior when La concentration increases for the Sr 2−y La y FeMoO 6 system.

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Raising the Curie temperature inSr2FeMoO6double perovskites by electron doping

Cited by 251 publications

References 12 publications

Theory of Half-Metallic Ferrimagnetism in Double Perovskites

Theory of Half-Metallic Ferrimagnetism in Double Perovskites

Unusual electron-doping effects inSr2−xLaxFeMoO6
Saitoh
¹
,
Nakatake
²
,
Nakajima
³

et al. 2005
Phys. Rev. B
19
2
13
0
View full text Add to dashboard Cite

Increase of Curie temperature with La doping in the double perovskite Sr2-LayFeMoO6 within an electronic correlation approach

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Raising the Curie temperature inSr2FeMoO6double perovskites by electron doping

Cited by 251 publications

References 12 publications

Theory of Half-Metallic Ferrimagnetism in Double Perovskites

Theory of Half-Metallic Ferrimagnetism in Double Perovskites

Unusual electron-doping effects inSr2−xLaxFeMoO6Saitoh1, Nakatake2, Nakajima3 et al. 2005Phys. Rev. B192130View full textAdd to dashboardCite

Increase of Curie temperature with La doping in the double perovskite Sr2-LayFeMoO6 within an electronic correlation approach

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Unusual electron-doping effects inSr2−xLaxFeMoO6
Saitoh
¹
,
Nakatake
²
,
Nakajima
³

et al. 2005
Phys. Rev. B
19
2
13
0
View full text Add to dashboard Cite