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Grain size-dependent magnetic and electric properties in nanosized YMnO3 multiferroic ceramics.

Han TC, Hsu WL, Lee WD - Nanoscale Res Lett (2011)

Bottom Line: The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 52 to 74 K.Further analysis suggests that the rising of AFM transition temperature with increasing grain size should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters.Furthermore, among all samples, the sample with grain size of 95 nm is found to have the smallest leakage current density (< 1 μA/cm2).PACS: 75.50.Tt, 75.50.Ee, 75.85.+t, 77.84.-s.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan. tchan@nuk.edu.tw.

ABSTRACT
Magnetic and electric properties are investigated for the nanosized YMnO3 samples with different grain sizes (25 nm to 200 nm) synthesized by a modified Pechini method. It shows that magnetic and electric properties are strongly dependent on the grain size. The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 52 to 74 K. A corresponding shift of the dielectric anomaly is observed, indicating a strong correlation between the electric polarization and the magnetic ordering. Further analysis suggests that the rising of AFM transition temperature with increasing grain size should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters. Furthermore, among all samples, the sample with grain size of 95 nm is found to have the smallest leakage current density (< 1 μA/cm2).PACS: 75.50.Tt, 75.50.Ee, 75.85.+t, 77.84.-s.

No MeSH data available.


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Temperature-dependent (a) dielectric constant (ε), and (b) loss tangent for the YMnO3 samples. Samples have different grain sizes (25 nm to 200 nm).
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Figure 6: Temperature-dependent (a) dielectric constant (ε), and (b) loss tangent for the YMnO3 samples. Samples have different grain sizes (25 nm to 200 nm).

Mentions: Figure 6 shows the temperature-dependent dielectric permittivity ε(T) and loss tangent (tanδ) at 100 kHz for all measured YMnO3 samples. In Figure 6a, the dielectric anomalies are observed at T* which is defined as the crossing point of two slopes as indicated by arrows. It shows that the T* shifts from 55 to 74 K with increasing grain sizes from 25 to 200 nm. As clearly apparent in Figure 6b, the positions of the broad peaks for the YMnO3 samples with different grains sizes are near their T*. Moreover, the enhanced dielectric response observed for YMnO3 with larger grains is similar to previously reported results for BaTiO3 dielectrics [19]. The observed systematic shift in the temperatures of magnetic transition and dielectric anomaly demonstrates a strong correlation between magnetic ordering and electric polarization in nanosized hexagonal YMnO3 ceramics. As to the coupling between antiferromagnetism and dielectric property, Katsufuji et al. [20] suggested that the dielectric anomaly was caused by the magnetic-ordering-dependent electronic excitation gap Eg in ab-plane. According to this model, the change of AFM ordering pattern can induce dielectric anomaly via the change of Eg, in a formula of ε = 1/Eg2. Therefore, one can understand that the shift in the temperature of dielectric anomalies is related to the AFM interaction through the variation of Mn-O bond length with change the lattice parameters. In addition, the systematical change in the lattice constant a plays an important role since the strength of AFM interactions strongly depends on the bond length of Mn-O. In general, the strength of AFM interaction can be written as [21]:(1)


Grain size-dependent magnetic and electric properties in nanosized YMnO3 multiferroic ceramics.

Han TC, Hsu WL, Lee WD - Nanoscale Res Lett (2011)

Temperature-dependent (a) dielectric constant (ε), and (b) loss tangent for the YMnO3 samples. Samples have different grain sizes (25 nm to 200 nm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211257&req=5

Figure 6: Temperature-dependent (a) dielectric constant (ε), and (b) loss tangent for the YMnO3 samples. Samples have different grain sizes (25 nm to 200 nm).
Mentions: Figure 6 shows the temperature-dependent dielectric permittivity ε(T) and loss tangent (tanδ) at 100 kHz for all measured YMnO3 samples. In Figure 6a, the dielectric anomalies are observed at T* which is defined as the crossing point of two slopes as indicated by arrows. It shows that the T* shifts from 55 to 74 K with increasing grain sizes from 25 to 200 nm. As clearly apparent in Figure 6b, the positions of the broad peaks for the YMnO3 samples with different grains sizes are near their T*. Moreover, the enhanced dielectric response observed for YMnO3 with larger grains is similar to previously reported results for BaTiO3 dielectrics [19]. The observed systematic shift in the temperatures of magnetic transition and dielectric anomaly demonstrates a strong correlation between magnetic ordering and electric polarization in nanosized hexagonal YMnO3 ceramics. As to the coupling between antiferromagnetism and dielectric property, Katsufuji et al. [20] suggested that the dielectric anomaly was caused by the magnetic-ordering-dependent electronic excitation gap Eg in ab-plane. According to this model, the change of AFM ordering pattern can induce dielectric anomaly via the change of Eg, in a formula of ε = 1/Eg2. Therefore, one can understand that the shift in the temperature of dielectric anomalies is related to the AFM interaction through the variation of Mn-O bond length with change the lattice parameters. In addition, the systematical change in the lattice constant a plays an important role since the strength of AFM interactions strongly depends on the bond length of Mn-O. In general, the strength of AFM interaction can be written as [21]:(1)

Bottom Line: The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 52 to 74 K.Further analysis suggests that the rising of AFM transition temperature with increasing grain size should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters.Furthermore, among all samples, the sample with grain size of 95 nm is found to have the smallest leakage current density (< 1 μA/cm2).PACS: 75.50.Tt, 75.50.Ee, 75.85.+t, 77.84.-s.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan. tchan@nuk.edu.tw.

ABSTRACT
Magnetic and electric properties are investigated for the nanosized YMnO3 samples with different grain sizes (25 nm to 200 nm) synthesized by a modified Pechini method. It shows that magnetic and electric properties are strongly dependent on the grain size. The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 52 to 74 K. A corresponding shift of the dielectric anomaly is observed, indicating a strong correlation between the electric polarization and the magnetic ordering. Further analysis suggests that the rising of AFM transition temperature with increasing grain size should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters. Furthermore, among all samples, the sample with grain size of 95 nm is found to have the smallest leakage current density (< 1 μA/cm2).PACS: 75.50.Tt, 75.50.Ee, 75.85.+t, 77.84.-s.

No MeSH data available.


Related in: MedlinePlus