Dynamic elastic response of KMn 1 − x Ca x F 3 : Elastic softening and domain freezing
Dynamic elastic response of KMn 1 − x Ca x F 3 : Elastic softening and domain freezing
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DOI：
10.1103/physrevb.80.094110
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发表时间：
2009-09
影响因子：
3.7
通讯作者：
W. Schranz;P. Sondergeld;A. Kityk;E. Salje
中科院分区：
文献类型：
--
作者：
W. Schranz;P. Sondergeld;A. Kityk;E. Salje
Results of continuous-wave resonance (MHz-region) and ultralow-frequency (Hz-region) dynamic mechanical analyzer measurements of pure ${\text{KMnF}}_{3}$ and mixed crystals ${\text{KMn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{F}}_{3}$ $(xl0.017)$ are presented in a broad temperature range including the phase-transition regions. The elastic anomalies depend strongly on the measurement frequency: The MHz-elastic constants can be well fitted by Landau theory including the difference between isothermal and adiabatic behavior. Contrary, at low frequencies (0.1--50 Hz) an elastic softening (superelasticity) due to domain-wall motion is found quite similar to that observed recently in isostructural ${\text{SrTiO}}_{3}$ [A. V. Kityk et al., Phys. Rev. B 61, 946 (2000)]. However, unlike to ${\text{SrTiO}}_{3}$, for the mixed system ${\text{KMn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{F}}_{3}$ we have measured freezing of the domain-wall movement around 100 K in a certain range of concentration of ${\text{Ca}}^{2+}$ ions $(x=0.003)$. Calculating the dynamic elastic response to the ac-stress field by taking into account the motion of randomly pinned ferroelastic domain walls in ${\text{KMn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{F}}_{3}$ yields excellent agreement between theory and experiment.
Results of continuous-wave resonance (MHz-region) and ultralow-frequency (Hz-region) dynamic mechanical analyzer measurements of pure ${\text{KMnF}}_{3}$ and mixed crystals ${\text{KMn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{F}}_{3}$ $(xl0.017)$ are presented in a broad temperature range including the phase-transition regions. The elastic anomalies depend strongly on the measurement frequency: The MHz-elastic constants can be well fitted by Landau theory including the difference between isothermal and adiabatic behavior. Contrary, at low frequencies (0.1--50 Hz) an elastic softening (superelasticity) due to domain-wall motion is found quite similar to that observed recently in isostructural ${\text{SrTiO}}_{3}$ [A. V. Kityk et al., Phys. Rev. B 61, 946 (2000)]. However, unlike to ${\text{SrTiO}}_{3}$, for the mixed system ${\text{KMn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{F}}_{3}$ we have measured freezing of the domain-wall movement around 100 K in a certain range of concentration of ${\text{Ca}}^{2+}$ ions $(x=0.003)$. Calculating the dynamic elastic response to the ac-stress field by taking into account the motion of randomly pinned ferroelastic domain walls in ${\text{KMn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{F}}_{3}$ yields excellent agreement between theory and experiment.