Structural, magnetic, and dielectric studies of the Aurivillius compounds SrBi5Ti4MnO18 and SrBi5Ti4Mn0.5Co0.5O18
Структурные, магнитные и диэлектрические исследования соединений Ауривиллиуса SrBi5Ti4MnO18 и SrBi5Ti4Mn0.5Co0.5O18
2015-01-13
SCID: 54.1/5p3h9t4a
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Arrhenius dielectric relaxationAurivillius compoundsCo2+ and Co3+Maxwell-Wagner effectMn3+ valence stateMn3+-O-Co3+ interactionSrBi5Ti4Mn0.5Co0.5O18SrBi5Ti4MnO18Vogel-Fulcher behaviorX-ray photoelectron spectroscopy (XPS)dc conductivity activation energyelectron paramagnetic resonance (EPR)ferrimagnetic transition (161 K)ferromagnetic transition (45 K)magnetodielectric effectmodified Pechini methodorthorhombic B2cb structureoxygen-vacancy collective motionrelaxor-like dielectric relaxationsuperparamagnetic state
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Abstract (AI)
We have successfully synthesized the Aurivillius compounds SrBi5Ti4MnO18 and SrBi5Ti4Mn0.5Co0.5O18 using a modified Pechini method. Both samples have an orthorhombic structure with the space group B2cb. The valence state of Mn is suggested to be +3 and the doped Co ions exist in the form of Co2+ and Co3+ based on the results of x-ray photoelectron spectroscopy. The sample SrBi5Ti4MnO18 exhibits a dominant paramagnetic state with the existence of superparamagnetic state as evidenced by the electron paramagnetic resonance results, whereas SrBi5Ti4Mn0.5Co0.5O18 undergoes a ferrimagnetic transition at 161 K originating from the antiferromagnetic coupling of Co-based and Mn-based sublattices, and a ferromagnetic transition at 45 K arising from the Mn3+-O-Co3+ (low spin) interaction. The sample SrBi5Ti4Mn0.5Co0.5O18 exhibits two dielectric anomalies. One corresponds to a relaxor-like dielectric relaxation which follows the Vogel-Fulcher function and the other dielectric relaxation obeys the Arrhenius law arising from the collective motion of oxygen vacancies. In addition, the sample SrBi5Ti4Mn0.5Co0.5O18 exhibits a magnetodielectric effect caused by the Maxwell-Wagner effect because of the conductivity of the sample. This is demonstrated by the fact that the activation energy in dielectric loss process is close to that for dc conductivity and the magnetodielectric effect is sensitive to the measured frequency.
Key Findings
1
SrBi5Ti4Mn0.5Co0.5O18 exhibits two dielectric anomalies: a relaxor-like relaxation following the Vogel-Fulcher law and an Arrhenius-type relaxation from collective oxygen-vacancy motion, plus a frequency-sensitive magnetodielectric effect attributed to Maxwell–Wagner mechanism linked to sample conductivity.
2
SrBi5Ti4Mn0.5Co0.5O18 shows a ferrimagnetic transition at 161 K (antiferromagnetic coupling between Co- and Mn-sublattices) and a ferromagnetic transition at 45 K (Mn3+-O-Co3+ low-spin interaction).
3
SrBi5Ti4MnO18 and SrBi5Ti4Mn0.5Co0.5O18 were synthesized by a modified Pechini method and both crystallize in orthorhombic B2cb structure.
4
SrBi5Ti4MnO18 is mainly paramagnetic with evidence of a superparamagnetic state from electron paramagnetic resonance.
5
X-ray photoelectron spectroscopy indicates Mn is predominantly +3, while doped Co exists as Co2+ and Co3+ in SrBi5Ti4Mn0.5Co0.5O18.
Research Object
Aurivillius oxide compounds SrBi5Ti4MnO18 and SrBi5Ti4Mn0.5Co0.5O18
Research Subject
Structural, magnetic, and dielectric properties including crystal structure and valence states, magnetic phases/transitions (paramagnetic, superparamagnetic, ferrimagnetic, ferromagnetic) and mechanisms, dielectric relaxations (Vogel–Fulcher and Arrhenius behaviors), oxygen-vacancy dynamics, and magnetodielectric effects
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2015-01-13
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