Does the self-trapped magnetic polaron exist in electron-doped manganites?

We show from ab initio density-functional calculations and model studies that, in the electron-doped manganite LaxCa1-xMnO3 (x<<1), unbound electrons are introduced into the conduction band, which then trap themselves in the exchange-induced magnetic potential wells forming the self-trapped magnetic polarons (STMP). Hopping beyond the nearest neighbors drastically reduces the binding energy, while the Jahn-Teller coupling increases it somewhat, resulting in a net binding of about 100+/-20 meV. The electron is self-trapped in a seven-site ferromagnetic region, beyond which the lattice is essentially antiferromagnetic. In light of the recent experiments of Neumeier and Cohn, our results suggest that the STMP may be present in the lightly electron-doped manganites.

[1]  Popovic,et al.  Electronic structure of the perovskite oxides: La1-xCaxMnO3. , 1996, Physical review letters.

[2]  J. Cohn,et al.  Heat conduction and magnetic phase behavior in electron-doped Ca1-xLaxMnO3 (0≤x≤0.2) , 2002, cond-mat/0208050.

[3]  Joshua Cohn,et al.  Possible signatures of magnetic phase segregation in electron-doped antiferromagnetic CaMnO 3 , 2000 .

[4]  I. Bersuker,et al.  The Jahn-Teller Effect and Vibronic Interactions in Modern Chemistry , 1984 .

[5]  Popovic,et al.  Cooperative jahn-teller coupling in the manganites , 2000, Physical review letters.

[6]  F. Aryasetiawan,et al.  Possible suppression of canted spin order in the double-exchange lanthanum manganites , 1997 .

[7]  J. Kanamori.  Crystal Distortion in Magnetic Compounds , 1960 .

[8]  Pickett,et al.  Electronic structure and half-metallic transport in the La1-xCaxMnO3 system. , 1996, Physical review. B, Condensed matter.

[9]  Nevill Mott,et al.  Metal-insulator transitions , 1974 .

[10]  Dagotto,et al.  Phase separation scenario for manganese oxides and related materials , 1999, Science.

[11]  J. V. Vleck.  The Jahn‐Teller Effect and Crystalline Stark Splitting for Clusters of the Form XY6 , 1939 .

[12]  Philip W. Anderson,et al.  Considerations on Double Exchange , 1955 .

[13]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[14]  S. Satpathy,et al.  Origin of charge-orbital order in the half-doped manganites. , 2002, Physical review letters.

[15]  Electronic structure of the perovskite oxides: La1-xCaxMnO3. , 1996 .

[16]  O. K. Andersen,et al.  Linear methods in band theory , 1975 .

[17]  Mills,et al.  Role of conduction-electron-local-moment exchange in antiferromagnetic semiconductors: Ferrons and bound magnetic polarons. , 1985, Physical review. B, Condensed matter.

[18]  P. de Gennes,et al.  Effects of Double Exchange in Magnetic Crystals , 1960 .

[19]  A. Yanase,et al.  Stability condition for the paramagnetic polaron in a magnetic semiconductor , 1970 .

[20]  Grenoble,et al.  ELECTRON-DOPED MANGANESE PEROVSKITES : THE MAGNETIC POLARON STATE , 1998, cond-mat/9807361.

[21]  Ove Jepsen,et al.  Explicit, First-Principles Tight-Binding Theory , 1984 .

[22]  Wang,et al.  Accurate and simple analytic representation of the electron-gas correlation energy. , 1992, Physical review. B, Condensed matter.

[23]  P. Wachter.  Photoconductivity of the magnetic semiconductor EuSe , 1970 .