Ultrasonic Attenuation near the Soft Mode Transition Point in KMnF<sub>3</sub>

Furukawa, Mutsuhisa; Fujimori, Yasunobu; Hirakawa, Kazuomi

doi:10.1143/jpsj.29.1528

Cited by 30 publications

(3 citation statements)

References 8 publications

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“…The use of the intensity of these satellite reflections to measure the order parameter is more problematic (Burandt et al 1994), since the domain microstructure in tetragonal KMnF 3 is highly variable, even within a single experiment (Tietze et al 1981, Hirakawa et al 1997. Experimental data also exist from ultrasonic studies of the soft mode (Furukawa et al 1970), and Raman spectroscopy (Kapusta et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Cubic-tetragonal phase transition in KMnF₃: excess entropy and spontaneous strain

Hayward

Romero

Gallardo

et al. 2000

J. Phys.: Condens. Matter

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The transition between cubic and tetragonal phases in KMnF3 has been studied by x-ray diffraction rocking curves and calorimetry. Comparison of the excess entropy with the order parameter Q obtained from spontaneous strain shows that the mean field relationship S Q 2 is obeyed to within experimental error. The data are fitted to a Landau free energy expression G = ½A (T -TC )Q 2 +(1/4) BQ 4 +(1/6)CQ 6 , with A = 2.781 J K-1 mol-1 , B = -57.63 J mol-1 , C = 574.2 J mol-1 , TC = 185.76 K. No significant excess specific heat is found at T >>TC .

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Section: Introductionmentioning

confidence: 99%

Cubic-tetragonal phase transition in KMnF₃: excess entropy and spontaneous strain

Hayward

Romero

Gallardo

et al. 2000

J. Phys.: Condens. Matter

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“…5 88 184 Heeger et al (1961) 16 81.5 88.3 Cooper and Nathans (1966) 17 88.1 Shirane et al (1970) 2 91.5 186. 6 Furukawa et al (1970) 18 186.7 19 184 3 195 Melcher and Plovnik (1971) 20 186.2 Saiki (1972) 21 81.5 88.3 Maartense and Searle (1972) 22 82 87.9 ± 0.1 184 Borsa (1973) 23 186 Hirotsu and Sawada (1973) 7 186 Fossheim et al (1974) 24 91.5 187. 5 Hidaka et al (1975) 25 81 88 91 Benard and Walker (1976) 26 80 89 184 Holt and Fossheim (1981) 27 187.…”

Section: Sourcementioning

confidence: 99%

“…Acoustic attenuation at higher frequencies (∼10-600 MHz) also reveals details of relaxation processes associated with the I → II transition. 18,24,27,67,76 These are believed to relate to the dynamics of ordered clusters just above T c1 , with some sensitivity to impurities, and Landau-Khalatnikov damping below T c1 , with relaxation times related to the order parameter dynamics, rather than to relaxation properties of the transformation microstructure. 27,76…”

Section: Elastic and Anelastic Properties Of Kmnfmentioning

confidence: 99%

Magnetoelastic coupling and multiferroic ferroelastic/magnetic phase transitions in the perovskite KMnF3

2012

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The magnetic, elastic, and anelastic behavior of single-crystal KMnF 3 have been investigated by superconducting quantum interference device (SQUID) magnetometry and resonant ultrasound spectroscopy (RUS) through the sequence of phase transitions: phase I, P m3m → (T c1 = 185 K) → phase II, I 4/mcm → (T c2 = T N = 87 K) → phase III, antiferromagnetic, Cmcm → (T c3 = 82 K) → phase IV, canted ferromagnet, Pnma. It is concluded that observed changes in the elastic properties can be explained simply in terms of strain/order parameter coupling for the octahedral tilting transitions. There appears to be no evidence in the present data or in data from the literature for coupling between the magnetic order parameter and shear strains. Any coupling between the magnetic and structural transitions is therefore weak, probably occurring only biquadratically through a small common volume strain. The combined data show unambiguously that, for the crystal used, the Néel point and the structural transition at 87 K are coincident. In other crystals, with slightly different stoichiometries and defect contents, this need not be the case, however, and the overlap of transition temperatures in KMnF 3 is essentially accidental. Strong acoustic dissipation at ∼0.1-1 MHz in the stability field of phase II is attributed to the local mobility of transformation twin walls under externally applied stress. A Debye-like loss peak near 130 K is attributed to pinning of at least some twin walls by defects, but relatively high levels of acoustic dissipation below this freezing temperature imply that some of the twin walls remain mobile due to weak pinning or the absence of any pinning. Acoustic losses continue in the stability field of phase III (Cmcm) but diminish substantially in the stability field of phase IV (Pnma), implying quite different twin mobilities in the different structure types. Overlap of the structural and magnetic instabilities in KMnF 3 opens up possibilities for manipulation of ferroelastic twinning by application of a magnetic field and for creation of materials in which the ferroelastic twin walls have quite different magnetic properties from the matrix in which they lie.

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SrLiH3 - DyAlO3

Nomura¹

Landolt-Börnstein - Group III Condensed Matter

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Ultrasonic Attenuation near the Soft Mode Transition Point in KMnF₃

Cited by 30 publications

References 8 publications

Cubic-tetragonal phase transition in KMnF₃: excess entropy and spontaneous strain

Cubic-tetragonal phase transition in KMnF₃: excess entropy and spontaneous strain

Magnetoelastic coupling and multiferroic ferroelastic/magnetic phase transitions in the perovskite KMnF3

SrLiH3 - DyAlO3

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Ultrasonic Attenuation near the Soft Mode Transition Point in KMnF3

Cited by 30 publications

References 8 publications

Cubic-tetragonal phase transition in KMnF3: excess entropy and spontaneous strain

Cubic-tetragonal phase transition in KMnF3: excess entropy and spontaneous strain

Magnetoelastic coupling and multiferroic ferroelastic/magnetic phase transitions in the perovskite KMnF3

SrLiH3 - DyAlO3

Contact Info

Product

Resources

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Ultrasonic Attenuation near the Soft Mode Transition Point in KMnF₃

Cubic-tetragonal phase transition in KMnF₃: excess entropy and spontaneous strain

Cubic-tetragonal phase transition in KMnF₃: excess entropy and spontaneous strain