Oxygen nonstoichiometry and magnetic properties of doped manganites La0.7Sr0.3Mn0.95Fe0.05O3-δ

In this work, solid solutions of La_0.7Sr_0.3Mn_0.95Fe_0.05O_3-δ with different oxygen content were obtained by the solid-phase reactions technique. Based on the investigation of the dynamics of changes in the oxygen index (3 – δ) during heating of the samples, the formation of a stressed state in their grains as a result of annealing was established. This results in a decrease in the mobility of oxygen vacancies during the reduction of cations according to the Mn⁴⁺ + e^– → Mn³⁺ scheme and explains the decrease of released oxygen amount with an increase of δ as well as the heating rate of the samples. When studying the magnetic properties of the obtained samples, it was found that the temperature dependence of the magnetization obeys the Curie–Weiss law and as the oxygen defficiency increases, the Curie temperature for solid solutions decreases. It was found that the particles are in a frozen ferromagnetic state when measured in the low-temperature region of the М(Т) dependence in “zero-field mode” at Т ˂ Т_В. The presence of ferromagnetism at Т ˃ Т_В leads to a magnetically ordered state, in which the resulting magnetic moment of the magnetic particle is influenced by thermal fluctuations. When considering the temperature values of the magnetization of lanthanum-strontium manganite samples, it was found that with an increase of temperature in the low-temperature region, magnetic ordering is disturbed due to the excitation of magnons with a quadratic dependence of the energy from the wave vector, the number of which increases in proportion to T^3/2. This results in a decrease in the manganite magnetization. The observed temperature dependence of the magnetization measured in the “field-cooling mode” was approximated taking into account the quadratic and non-quadratic dispersion laws of the magnon spectrum.

1. Goodenough J.B. Electronic and ionic transport properties and other physical aspects of perovskites. Reports on Progress in Physics. 2004; 67: 1915—1994. https://doi.org/10.1088/0034-4885/67/11/R01

2. Dunaevsky S.M. Magnetic phase diagrams of manganites in the area of their electronic doping (a Review). Fizika Tverdogo Tela. 2004; 46(2): 193—211. (In Russ.)

3. Balagurov A.M., Bushmeleva S.N., Pomjakushin V.Yu., Sheptyakov D.V., Amelichev V.A., Gorbenko O.Yu., Kaul A.R., Gan’shina E.A., Perkins N.B. Magnetic structure of NaMnO3 consistently doped with Sr and Ru. Phys. Rev. B. 2004; 70: 014427. https://doi.org/10.1103/PhysRevB.70.014427

4. Kozlenko D.P., Glazkov V.P., Jirák Z., Savenko B.N. High pressure effects on the crystal and magnetic structure of Pr1-xSrxMnO3 manganites (x = 0.5–0.56). J. Phys.: Condensed Matter. 2004; 16(13): 2381—2394. https://doi.org/10.1088/0953-8984/16/13/017

5. Nagaev E.L. Lanthanum manganites and other giant-magnetoresistance magnetic conductors. Physics – Uspekhi. 1996; 39(8): 781—806. https://doi.org/10.1070/ PU1996v039n08ABEH000161

6. Yanchevskii O.Z., V’yunov O.I., Belous A.G., Tovstolytkin A.I., Kravchik V.P. Synthesis and properties of La0.7Sr0.3Mn1-xTixO3. Fizika Tverdogo Tela. 2006; 48(4): 667—673. (In Russ.)

7. McIntosh S., Vente J.F., Haije W.G., Blank D.H.A., Bouwmeester H.J.M. Structure and oxygen stoichiometry of SrCo0.8Fe0.2O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ. Solid State Ionics. 2006; 177(19–25): 1737—1742. https://doi.org/10.1016/j.ssi.2006.03.041

8. Maignan A., Martin C., Pelloquin D., Nguyen N., Raveau B. Structural and magnetic studies of ordered oxygen-deficient perovskites LnBaCo2O5+δ, closely related to the ‘‘112’’ structure. J. Solid State Chem. 1999; 142(2): 247—260. https://doi.org/10.1006/jssc.1998.7934

9. Yamazoe N., Furukawa S., Teraoka Y., Seiyama T. The effect of oxygen sorption on the crystal structure of La1-xSrxCoO3-δ. Chem. Lett. 1982; 11(12): 2019—2022. https://doi.org/10.1246/cl.1982.2019

10. Deshmukh A.V., Patil S.I., Bhagat S.M., Sagdeo P.R., Choudhary R.J., Phase D.M. Effect of iron doping on electrical, electronic and magnetic properties of La0.7Sr0.3MnO3. J. Phys. D: Appl. Phys. 2009; 42(18): 185410. https://doi.org/10.1088/0022-3727/42/18/185410

11. Barik S.K., Mahendiran R. Ac magnetotransport in La0.7Sr0.3Mn0.95Fe0.05O3 at low dc magnetic fields. Solid State Communications. 2011; 151(24): 1986—1989. https://doi.org/10.1016/j.ssc.2011.09.007

12. Ritter C., Ibarra M.R., Morellon L., Blasco J., Garcia J., De Teresa J.M. Structural and magnetic properties of double perovskites AA’FeMoO6 (AA’ = Ba2, BaSr, Sr2 and Ca2). J. Phys.: Condensed Matter. 2000; 12(38): 8295—8308. https://doi.org/10.1088/0953-8984/12/38/306

13. dos Santos–Gómez L., Leon-Reina L., Porras-Vazquez J.M., Losilla E.R., Marrero-Lopez D. Chemical stability and compatibility of double perovskite anode materials for SOFCs. Solid State Ionics. 2013; 239: 1—7. https://doi.org/10.1016/j.ssi.2013.03.005

14. Huang Q., Li Z.W., Li J., Ong, C.K. The magnetic, electrical transport and magnetoresistance properties of epitaxial La0.7Sr0.3Mn1-xFexO3 (x = 0–0.20) thin films prepared by pulsed laser deposition. J. Phys.: Condensed Matter. 2001; 13(18): 4033—4048. https://doi.org/10.1088/0953-8984/13/18/312

15. Kruidhof H., Bouwmeester H.J.M., v. Doorn R.H.E., Burggraaf A.J. Influence of order-disorder transitions on oxygen permeability through selected nonstoichiometric perovskite-type oxides. Solid State Ionics. 1993; 63–65: 816—822. https://doi.org/10.1016/0167-2738(93)90202-E

16. Kuo J.H., Anderson H.U., Sparlin D.M. Oxidation-reduction behavior of undoped and Sr-doped LaMnO3: defect structure, electrical conductivity, and thermoelectric power. J. Solid State Chem. 1990; 87(1): 55—63. https://doi.org/10.1016/0022-4596(90)90064-5

17. Ulyanov A.N., Mazur A.S., Yang D.C., Krivoruchko V.N., Danilenko I.A., Konstantinova T.E., Levchenko G.G. Local structural and magnetic inhomogeneities in nanosized La0.7Sr0.3MnO3 manganites. Nanosystems, Nanomaterials, Nanotechnologies. 2011; 9(1): 107—114. (In Russ.)

18. Krivoruchko V.N., Marchenko M.A. Modeling of the hysteresis properties of the (LаSr)MnО3 nanostructured samples. Fizika Niskikh Temperatur. 2008; 34(9): 947–955. (In Russ.)

19. Ziese M., Vrejoiu I., Setzer A., Lotnyk A., Hesse D. Coupled magnetic and structural transitions in La0.7Sr0.3MnO3 films on SrTiO3. New J. Phys. 2008; 10: 063024. https://doi.org/10.1088/1367-2630/10/6/063024

20. Mizusaki J., Mori N., Takai H., Yonemura Y., Minamiue H., Tagawa H., Dokiya M., Inaba H., Naraya K., Sasamoto T., Hashi­moto T. Oxygen nonstoichiometry and defect equilibrium in the perovskite-type oxides La1-xSrxMnO3+d. Solid State Ionics. 2000; 129(1–4): 163—177. https://doi.org/10.1016/S0167-2738(99)00323-9

21. Jimenes M., Martinez J.L., Herrero E., Alonso J., Prieto C., de Andres A., Vallet-Regi M., Gonzalez-Calbet J., Fernandez-Diaz M.T. Structural and magnetoresistance study of LaxMnyO3±z. Phys. B: Condensed Matter. 1997; 234–236: 708—709. https://doi.org/10.1016/S0921-4526(96)01110-6

22. Aruna S.T., Muthuraman M., Patil K.C. Combustion synthesis and properties of strontium substituted lanthanum manganites La1-xSrxMnO3 (0≤x≤0.3). J. Mater. Chem. 1997; 7(12): 2499—2503. https://doi.org/10.1039/A703901H

23. De Leon-Guevara A.M., Berthet P., Berthon J., Millot F., Revcolevschi A., Anane A., Dupas C., Le Dang K., Renard J.P., Veillet P. Influence of controlled oxygen vacancies on the magnetotransport and magnetostructural phenomena in La0.85Sr0.15MnO3-δ single crystals. Phys. Rev. B. 1997; 56(10): 6031. https://doi.org/10.1103/PhysRevB.56.6031

24. Veverka P., Kaman O., Knížek K., Novák P., Maryško M., Jirák Z. Magnetic properties of rare-earth-doped La0.7Sr0.3MnO3. J. Phys.: Condensed Matter. 2016; 29(3): 035803. https://doi.org/10.1088/1361-648X/29/3/035803

25. Mizusaki J., Tagawa H., Naraya K., Sasamoto T. Nonstoichiometry and thermochemical stability of the perovskite-type La1-xSrxMnO3-δ. Solid State Ionics. 1991; 49: 111—118. https://doi.org/10.1016/0167-2738(91)90076-N

26. Kuo J.H., Anderson H.U., Sparlin D.M. Oxidation-reduction behavior of undoped and Sr-doped LaMnO3: defect structure, electrical conductivity, and thermoelectric power. J. Solid State Chem. 1990; 87(1): 55—63. https://doi.org/10.1016/0022-4596(90)90064-5

27. Rodríguez-Carvajal J. Recent developments of the program FULLPROF. Commission on powder diffraction (IUCr). Newsletter. 2001; 26: 12—19.

28. Kraus W. POWDER CELL — a program for the representation and manipulation of crystal structures and calculation of the resulting X-ray powder patterns. J. Appl. Crystallography. 1996; 29(3): 301—303. https://doi.org/10.1107/S0021889895014920

29. Dyson F.J. Thermodynamic behavior of an ideal ferromagnet. Phys. Rev. 1956; 102(5): 1230—1244. https://doi.org/10.1103/PhysRev.102.1230