Abstract
The influence of annealing in strongly reducing atmosphere on the magnetic properties of hexagonal BaTiO3 + 0.04 BaO + x/2 Co2O3 (0.0025 ≤ x ≤ 0.10) ceramics was investigated. The samples air-sintered at 1673 K were subsequently tempered at 1473 K in H2/Ar stream. While the as-sintered samples exclusively exhibit paramagnetic behavior, the annealed samples show distinct saturation in the field dependence of the magnetization at 300 K measured in the range between −90 and 90 kOe. Besides, the field dependence of the magnetization is hysteretic with coercive fields in the order of 100 Oe. Both properties point to ferromagnetic regions which were identified as precipitations of metallic cobalt by TEM and EDX. The cobalt precipitations were exclusively found in tetragonal grains which were completely Co-free outside the precipitations. Obviously, these tetragonal grains were formed during the annealing process when the Co content of the formerly hexagonal grains was concentrated into metallic Co particles by diffusion processes. Hence, the Co-free matrix of the grains transformed into the cubic phase which is the equilibrium phase of undoped BaTiO3 at the annealing temperature 1473 K and during cooling to room temperature into tetragonal phase. The size of the metallic precipitations ranges from about 20 to 100 nm. A reduction both of the annealing temperature to 1373 K and of the annealing time from 120 to 30 min did not change the minimum particle size, but now, the very rare precipitations only occurred at triple points or grain boundaries. EPR measurements confirmed the occurrence of the ferromagnetic precipitations. While at 300 K, the as-sintered samples did not show any Co EPR signal, the annealing in strongly reducing atmosphere caused a strong and broad line which is attributed to the ferromagnetic resonance signal of the Co precipitations. The investigations were extended for the dopants, iron or nickel, with a nominal sample composition of BaTiO3 + 0.04 BaO + 0.01 Fe2O3 or 0.02 NiO, respectively. The field dependence of the magnetization as well as the EPR spectra showed similar results compared to the case of Co-doped samples. Hence, also in Fe- or Ni-doped BaTiO3 ceramics, ferromagnetic properties are caused by annealing in strongly reducing atmosphere.
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Notes
The slight Ba-excess supports the preferred incorporation of Co on Ti sites in the air-sintered samples [17].
For a qualitative discussion, the chosen Co concentration x = 0.01 is sufficiently near the concentration x = 0.015 used for the TEM/STEM investigations. .
Here, molecular field means the summarized contributions of magnetic dipole–dipole, exchange, electrostatic multipole, and electron–phonon interactions.
References
Rabe K, Ahn ChH, Triscone JM (2007) Physics of ferroelectrics: a modern perspective. Springer, Berlin
Kitagawa Y, Hiraoka Y, Honda T, Ishikura T, Nakamura H, Kimura T (2010) Low-field magnetoelectric effect at room temperature. Nat Mater 9:797–802
Possenriede E, Jacobs P, Schirmer OF (1992) Paramagnetic defects in BaTiO3 and their role in light-induced charge transport: I ESR studies. J Phys 4:4719–4742
Possenriede E (1992) Paramagnetische Störstellen in Bariumtitanat und ihre lichtinduzierten Umladungen. Dissertation, University of Osnabrück, Germany
Lee JS, Khim ZG, Park YD, Norton DP, Theodoropoulou NA, Budai JD, Boatner SJ, Pearton SJ, Wilson RG (2003) Magnetic properties of Co- and Mn-implanted BaTiO3, SrTiO3 and KTaO3. Solid State Electron 47:2225–2230
Khalitov NI, Khaibullin RI, Valeev VF, Dulov EN, Ivoilov NG, Tagirov LR, Kazan S, Sale AG, Mikailzade FA (2012) Structural and magnetic studies of Co and Fe implanted BaTiO3 crystals. Nucl Instrum Methods Phys Res B 272:104–107
Maier R, Cohn JL, Neumeier JJ, Bendersky LA (2001) Ferroelectricity and ferrimagnetism in iron-doped BaTiO3. Appl Phys Lett 78:2536–2538
Rajamani A, Dionne GF, Bono D, Ross J (2005) Faraday rotation, ferromagnetism, and optical properties in Fe-doped BaTiO3. J Appl Phys 98:3907
Ramana EV, Yang SM, Jung R, Jung MH, Lee BW, Jung CU (2013) Ferroelectric and magnetic properties of Fe-doped BaTiO3 thin films grown by the pulsed laser deposition. J Appl Phys 113:187219
Lin F, Shi W (2009) Magnetic properties of transition-metal-codoped BaTiO3 systems. J Alloys Compd 475:64–69
Ray S, Mahadevan P, Mandal S, Krishnakumar SR, Kuroda CS, Sasaki T, Taniyama T, Itoh M (2008) High temperature ferromagnetism in single crystalline dilute Fe-doped BaTiO3. Phys Rev B 77:104416
Du G-P, Hu Z-J, Han Q-F, Qin X-M, Shi W-Z (2010) Effects of niobium donor doping on the phase structures and magnetic properties of Fe-doped BaTiO3 ceramics. J Alloys Compd 492:L79–L81
Chakraborty T, Ray S, Itoh M (2011) Defect-induced magnetism: test of dilute magnetism in Fe-doped hexagonal BaTiO3 single crystals. Phys Rev B 83:144407
Chakraborty T, Meneghini C, Aquilanti G, Ray S (2014) Investigating the development of spurious magnetism in single crystalline BaTi0.95Fe0.05O3-δ with high δ by local structural probes. J Phys: Condens Matter 26:196001
Valant M, Arčon I, Mikulska I, Lisjak D (2013) Cation order–disorder transition in Fe-doped 6h-batio3 for dilute room-temperature ferromagnetism. Chem Mater 25:3544–3550
Zorko A, Pregelj M, Gomilšek M, Jagličić Z, Pajić D, Telling M, Arčon I, Mikulska I, Valant M (2015) Strain-induced extrinsic high-temperature ferromagnetism in the Fe-doped hexagonal barium titanate. Sci Rep 5:7703
Langhammer HT, Böttcher R, Müller T, Walther T, Ebbinghaus SG (2015) Defect properties of cobalt-doped hexagonal barium titanate ceramics. J Phys: Condens Matter 27:295901
Rečnik A, Kolar D (1996) Exaggerated growth of hexagonal barium titanate under reducing sintering conditions. J Am Ceram Soc 79:1015–1018
Kolar D, Kunaver U, Rečnik A (1998) Exaggerated anisotropic grain growth in hexagonal barium titanate ceramics. Phys Status Solidi A 166:219–230
Langhammer HT, Müller T, Felgner K-H, Abicht H-P (2000) Crystal structure and related properties of manganese-doped barium titanate ceramics. J Am Ceram Soc 83:605–611
Langhammer HT, Müller T, Böttcher R, Abicht H-P (2003) Crystal structure and related properties of copper-doped barium titanate ceramics. Solid State Sci 5:965–971
Langhammer HT, Müller T, Böttcher R, Abicht H-P (2008) Structural and optical properties of chromium-doped hexagonal barium titanate ceramics. J Phys: Condens Matter 20:085206
Bean CP, Livingston JD (1959) Superparamagnetism. J Appl Phys 30:120S–129S
O’Handley RC (2000) Modern magnetic materials: principles and applications. Wiley, New York
Wang J-Q, Xiao G (1994) Transition-metal granular solids: microstructure, magnetic properties, and giant magnetoresistance. Phys Rev B 49:3982–3996
Böttcher R, Langhammer HT, Müller T, Abicht H-P (2008) 3C–6H phase transition in BaTiO3 induced by Fe ions: an electron paramagnetic resonance study. J Phys: Condens Matter 20:505209
Langhammer HT, Müller T, Walther T (to be published)
Geiler AL, Harris VG, Vittoria C, Sun NX (2006) A quantitative model for the nonlinear response of fluxgate magnetometers. J Appl Phys 99:08B316.
Blundell S (2001) Magnetism in condensed matter. Oxford University Press, Oxford
Böttcher R, Langhammer HT, Müller T (2011) Paramagnetic resonance study of nickel ions in hexagonal barium titanate. J Phys: Condens Matter 23:115903.
Figueras FG, Amorim CO, Amaral J, Agostinho Moreira J, Tavares PB, Alves E, Amaral VS (2016) Magnetoelectric effect probe through ppm Fe doping in BaTiO3. J Alloys Compd 661:495–500
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Langhammer, H.T., Müller, T., Walther, T. et al. Ferromagnetic properties of barium titanate ceramics doped with cobalt, iron, and nickel. J Mater Sci 51, 10429–10441 (2016). https://doi.org/10.1007/s10853-016-0263-3
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DOI: https://doi.org/10.1007/s10853-016-0263-3