Investigation Of The Local Fe Magnetic Moments At The Grain Boundaries Of The Ca2 Fere O6 Double Perovskite

The local Fe ferromagnetic (FM) moment at the grain boundaries of a ceramic sample of Ca2 FeRe O6 double perovskite was investigated by means of x-ray magnetic circular dichroism spectroscopy at the Fe L2,3 edges and compared to the overall bulk magnetization. We found that, at the grain boundaries, the Fe FM moments at H=5 T are much smaller than expected and that the M×H curve is harder than in the bulk magnetization. These results suggest a larger degree of FeRe antisite disorder at the grain boundaries of this sample, shedding light into the intriguing nonmetallic resistivity behavior despite the reported presence of free carriers. © 2007 American Institute of Physics.1019Serrate, D., De Teresa, J.M., Ibarra, M.R., (2007) J. Phys.: Condens. Matter, 19, p. 023201Kobayashi, K.-I., Kimura, T., Sawada, H., Terakura, K., Tokura, Y., (1998) Nature (London), 395, p. 677Kobayashi, K.-I., Kimura, T., Tomoika, Y., Sawada, H., Terakura, K., Tokura, Y., (1999) Phys. Rev. B, 59, p. 11. , 159Prellier, W., Smolyaninova, V., Biswas, A., Galley, C., Greene, R.L., Ramesha, K., Gopalakrishnan, J., (2000) J. Phys.: Condens. Matter, 12, p. 965Gopalakrishnan, J., Chattopadhyay, A., Ogale, S.B., Venkatesan, T., Greene, R.L., Millis, A.J., Ramesha, K., Marest, G., (2000) Phys. Rev. B, 62, p. 9538Maignan, A., Raveau, B., Martin, C., Hervieu, M., (1999) J. Solid State Chem., 144, p. 224Dai, J.M., (2001) Mater. Sci. Eng., B, 83, p. 217Sarma, D.D., Mahadevan, P., Saha-Dasgupta, T., Ray, S., Kumar, A., (2000) Phys. Rev. Lett., 85, p. 2549Fang, Z., Terakura, K., Kanamori, J., (2001) Phys. Rev. B, 63, p. 180407Wu, H., (2001) Phys. Rev. B, 64, p. 125126Szotek, Z., Temmerman, W.M., Svane, A., Petit, L., Winter, H., (2003) Phys. Rev. B, 68, p. 104411Chattopadhyay, A., Millis, A.J., (2001) Phys. Rev. B, 64, p. 024424Aligia, A.A., Petrone, P., Sofo, J.O., Alascio, B., (2001) Phys. Rev. B, 64, p. 092414Kato, H., Okuda, T., Okimoto, Y., Tomoika, Y., Oikawa, K., Kamiyama, T., Tokural, Y., (2002) Phys. Rev. B, 65, p. 144404Westerburg, W., Lang, O., Ritter, C., Felser, C., Tremel, W., Jakob, G., (2002) Solid State Commun., 122, p. 201Oikawa, K., Kamiyama, T., Kato, H., Tokura, Y., (2003) J. Phys. Soc. Jpn., 72, p. 1411Granado, E., Huang, Q., Lynn, J.W., Gopalakrishnan, J., Greene, R.L., Ramesha, K., (2002) Phys. Rev. B, 66, p. 064409Iwasawa, H., Saitoh, T., Yamashita, Y., Ishii, D., Kato, H., Hamada, N., Tokura, Y., Sarma, D.D., (2005) Phys. Rev. B, 71, p. 075106Longo, J., Ward, R., (1961) J. Am. Chem. Soc., 83, p. 2816Alamelu, T., Varadaraju, U.V., Venkatesan, M., Douvalis, A.P., Coey, J.M.D., (2002) J. Appl. Phys., 91, p. 8909Serrate, D., De Teresa, J.M., Algarabel, P.A., Marquina, C., Morellon, L., Blasco, J., Ibarra, M.R., (2005) J. Magn. Magn. Mater., 290-291, p. 843De Teresa, J.M., Serrate, D., Blasco, J., Ibarra, M.R., Morellon, L., (2004) Phys. Rev. B, 69, p. 144401De Teresa, J.M., Serrate, D., Blasco, J., Ibarra, M.R., Morellon, L., (2005) J. Magn. Magn. Mater., 290-291, p. 1043Sikora, M., (2006) Appl. Phys. Lett., 89, p. 062509Azimonte, C., Cezar, J.C., Granado, E., Huang, Q., Lynn, J.W., Campoy, J.C.P., Gopalakrishnan, J., Ramesha, K., (2007) Phys. Rev. Lett., 98, p. 017204Abbate, M., (1992) Phys. Rev. B, 46, p. 4511Regan, T.J., Ohldag, H., Stamm, C., Nolting, F., Lning, J., Sthr, J., White, R.L., (2001) Phys. Rev. B, 64, p. 214422Thole, B.T., Carra, P., Sette, F., Van Der Laan, G., (1992) Phys. Rev. Lett., 68, p. 1943Carra, P., Thole, B.T., Altarelli, M., Wang, X.D., (1993) Phys. Rev. Lett., 70, p. 694Stohr, J., König, H., (1995) Phys. Rev. Lett., 75, p. 3748Teramura, Y., Tanaka, A., Jo, T., (1996) J. Phys. Soc. Jpn., 65, p. 105

Orbital reconstruction and two-dimensional electron gas at the LaAlO3/SrTiO3 interface

Conventional two-dimensional electron gases are realized by engineering the interfaces between semiconducting compounds. In 2004, Ohtomo and Hwang discovered that an electron gas can be also realized at the interface between large gap insulators made of transition metal oxides [1]. This finding has generated considerable efforts to clarify the underlying microscopic mechanism. Of particular interest is the LaAlO3/SrTiO3 system, because it features especially striking properties. High carrier mobility [1], electric field tuneable superconductivity [2] and magnetic effects [3], have been found. Here we show that an orbital reconstruction is underlying the generation of the electron gas at the LaAlO3/SrTiO3 n-type interface. Our results are based on extensive investigations of the electronic properties and of the orbital structure of the interface using X-ray Absorption Spectroscopy. In particular we find that the degeneracy of the Ti 3d states is fully removed, and that the Ti 3dxy levels become the first available states for conducting electrons.Comment: 12 pages, 3 figure