Ordered La0.7Sr0.3MnO3 nanohole arrays fabricated on a nanoporous alumina template by pulsed laser ablation

Highly ordered nanohole arrays of [Formula: see text] manganite have been synthesized using pulsed laser deposition on nanoporous alumina template. Their structure and phase formation were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). The magnetic measurements were performed with respect to temperature and field and exhibit a ferromagnetic to paramagnetic transition at 284 K. In addition, the temperature dependence of electrical resistance was measured at different magnetic fields and an insulating phase throughout all the temperatures was observed. The low temperature ferromagnetic insulating state is discussed by the presence of a canted ferromagnetic state induced by the nanoholes. The present work shows the feasibility of combining both the nanoporous alumina template and pulsed laser ablation for the fabrication of perovskite manganite nanohole arrays which can also be extended to fabricate other multicomponent oxide nanohole materials.M K is thankful to FCT, Portugal for the Grant No. SFRH/ BPD/75110/2010. The authors acknowledged the financial supports from the projects NORTE-07–0124-FEDER000070, CERN/FIS-NUC/0004/2015 and IF/00686/2014

Effects Of Ru Doping On The Transport And Magnetic Properties Of A La 1.32sr1.68mn2 - Yruyo7 Layered Manganite System

The low temperature magnetization, specific heat, electrical resistance and magnetoresistance have been studied for the Ru-doped La1.32Sr 1.68Mn2 - yRuyO7 (y = 0.0, 0.04, 0.08 and 0.15) layered manganite system. The undoped compound (y = 0.0) shows a sharp ferromagnetic transition (TC) accompanied by a metal-insulator transition (TMI) at 118K. The Ru substitution decreases the T C and TMI temperatures significantly. The temperature dependence of specific heat measurement confirms the decrease in TC by observing the anomaly corresponding to TC. The decreased effective moments from 3.48 μB for the undoped compound to 1.82μB for the highly doped compound at 5K indicates the Ru substitution weakens the ferromagnetic order in the low temperature regime and reduces the number of Mn pairs in the highly doped sample. The field dependence of magnetization measurements exhibits an enhancement of the coercive field with increased Ru concentration and gives evidence for the mixed magnetic phase for the highly doped compound. For the undoped sample, a large negative magnetoresistance of 300% at TC and 128% at 4.2K in a 5T field were observed. The magnetoresistance ratio decreases gradually with increasing Ru substitution. We find that the doped Ru in the Mn site drives the layered manganite system towards a magnetically mixed state. The effects of Ru doping in the transport and magnetic properties will be explained by the antiferromagnetically coupled Ru and Mn sublattices. © 2010 IOP Publishing Ltd.2223Kimura, T., Tokura, Y., (2000) Annu. Rev. Mater. Sci., 30, p. 451Ling, C.D., Millburn, J.E., Mitchell, J.F., Argyriou, D.N., Linton, J., Bordallo, H.N., (2000) Phys. Rev., 62, p. 15096Mitchell, J.F., Ling, C.D., Millburn, J.E., Argyriou, D.N., Berger, A., Medarde, M., (2001) J. Appl. Phys., 89, p. 6618Zener, C., (1951) Phys. Rev., 82, p. 403Millis, A.J., Littlewood, P.B., Shraiman, B.I., (1995) Phys. Rev. Lett., 74, p. 5144Wang, A., Cao, G., (2006) J. Magn. Magn. Mater., 305, p. 520Zhang, J., Yan, Q., Wang, F., Yuan, P., Zhang, P., (2000) J. Phys.: Condens. Matter, 12, p. 1981Sahu, R.K., Sundar Manoharan, S., Mohammad, Q., Rao, M.L., Nigam, A.K., (2002) J. Appl. Phys., 91, p. 7724Nair, S., Banerjee, A., (2004) Phys. Rev., 70, p. 104428Kumaresavanji, M., Reis, M.S., Xing, Y.T., Fontes, M.B., (2009) J. Appl. Phys., 106, p. 093709MacHado, F.L.A., Clark, W.G., (1988) Rev. Sci. Instrum., 59, p. 1176Kubota, M., Fujioka, H., Hirota, K., Ohoyama, K., Moritomo, Y., Yoshizawa, H., Endoh, Y., (2000) J. Phys. Soc. Japan, 69, p. 1606Wang, A., Cao, G., Liu, Y., Long, Y., Li, Y., Feng, Z., Ross, J.H., (2005) J. Appl. Phys., 97, p. 103906Argyriou, D.N., Mitchell, J.F., Potter, C.D., Bader, S.D., Kleb, R., Jorgensen, J.D., (1997) Phys. Rev., 55, p. 11965Osborn, R., Rosenkranz, S., Argyriou, D.N., Doloc, L.V., Lynn, J.W., Sinha, S.K., Mitchell, J.F., Bader, S.D., (1998) Phys. Rev. Lett., 81, p. 3964Zhang, Q., Zhang, W., Jiang, Z., (2005) Phys. Rev., 72, p. 142401Okuda, T., Kimura, T., Tokura, Y., (1999) Phys. Rev., 60, p. 3370Shannon, R.D., Prewitt, C.T., (1969) Acta Crystallogr., 25, p. 925Butera, A., Fainstein, A., Winkler, E., Tallon, J., (2001) Phys. Rev., 63, p. 054442Ying, Y., Fan, J., Pi, L., Qu, Z., Wang, W., Hong, B., Tan, S., Zhang, Y., (2006) Phys. Rev., 74, p. 144433Dagotto, E., Hotta, T., Moreo, A., (2001) Phys. Rep., 344, p. 1Weigand, F., Gold, S., Schmid, A., Geissler, J., Goering, E., Dorr, K., Krabbes, G., Ruck, K., (2002) Appl. Phys. Lett., 81, p. 2035Siwach, P.K., Singh, H.K., Srivastava, O.N., (2008) J. Phys.: Condens. Matter, 20, p. 273201Kimura, T., Tomioka, Y., Kuwahara, H., Asamitsu, A., Tamura, M., Tokura, Y., (1996) Science, 274, p. 1698Julliere, M., (1975) Phys. Lett., 54, p. 225Moodera, J.S., Nassar, J., Mathon, G., (1999) Annu. Rev. Mater. Sci., 29, p. 38

Effects of Ru doping on the transport and magnetic properties of a La1.32Sr1.68Mn2-yRuyO7 layered manganite system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The low temperature magnetization, specific heat, electrical resistance and magnetoresistance have been studied for the Ru-doped La1.32Sr1.68Mn2-yRuyO7 (y = 0.0, 0.04, 0.08 and 0.15) layered manganite system. The undoped compound (y = 0.0) shows a sharp ferromagnetic transition (T-C) accompanied by a metal-insulator transition (T-MI) at 118 K. The Ru substitution decreases the T-C and T-MI temperatures significantly. The temperature dependence of specific heat measurement confirms the decrease in T-C by observing the anomaly corresponding to T-C. The decreased effective moments from 3.48 mu(B) for the undoped compound to 1.82 mu(B) for the highly doped compound at 5 K indicates the Ru substitution weakens the ferromagnetic order in the low temperature regime and reduces the number of Mn pairs in the highly doped sample. The field dependence of magnetization measurements exhibits an enhancement of the coercive field with increased Ru concentration and gives evidence for the mixed magnetic phase for the highly doped compound. For the undoped sample, a large negative magnetoresistance of 300% at T-C and 128% at 4.2 K in a 5 T field were observed. The magnetoresistance ratio decreases gradually with increasing Ru substitution. We find that the doped Ru in the Mn site drives the layered manganite system towards a magnetically mixed state. The effects of Ru doping in the transport and magnetic properties will be explained by the antiferromagnetically coupled Ru and Mn sublattices.2223Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Third World Academy of Sciences (TWAS), ItalyFundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [470940/2007-7]APQ1-FAPERJ [E26/170.717/2007]Pronex-FAPERJ [E-26/171.165/2003]Cientistas do Estado-FAPERJ [E-26/102.700/2008