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| Home > Publications database > Acoustic Instabilities of CuFe2O4 |
| Poster (Invited) | FZJ-2024-06881 |
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2024
Abstract: MotivationThe tetragonal distortion in spinel structures, such as CuFe2O4, CuCr2O4, and NiCr2O4, has garneredsignificant attention due to its profound influence on structural and magnetic properties [1].Among these, CuFe2O4 is unique as it is ferromagnetic at room temperature. The tetragonal distortionin CuFe2O4 has been explained using semicovalent bonding [2] and the Jahn-Teller effect [3].The transition from a tetragonal to a cubic structure upon heating has been the subject of ongoingresearch. Bertaut [4] initially proposed a transition temperature of 760℃, but subsequent studiesby Miyahara and Ohnishi [5] using high-temperature X-ray diffraction and heat analysis correctedthis value to approximately 400℃. This transition occurs below the magnetic Curie temperature,highlighting the coupling between structural and magnetic properties. Additionally, Takei et al. [6]and Forrer et al. [7] observed anomalies near 390℃, consistent with this structural phase transition.These findings motivate further studies on CuFe2O4 to understand its temperature-dependentstructural transitions, magnetoelastic coupling, and associated changes in elastic constants. Such investigationsprovide key insights into the material’s fundamental physics and potential applicationsin magnetostrictive and multiferroic devices.Findings and future planCuFe2O4 demonstrates complex structural and acoustic transitions driven by temperature variations.The tetrahedral structure transitions to a cubic phase with increasing temperature as evidenced byX-ray diffraction. Elastic neutron scattering reveals temperature-induced changes in the Lorentzianscale and width. The scale decreases with increasing temperature, while the width broadens, indicatingevolving elastic properties. These trends align with fitting models, confirming the consistencyof our interpretation.Inelastic neutron scattering along Q = [1,￣1, 0] at room temperature reveals the relationship betweenthe Lorentzian peak position and the acoustic rate. The acoustic rate, defined by the Lorentzian peakposition, is directly linked to the elastic constant c11-c12. Shifts in the Lorentzian peak position andwidth with increasing temperature provide insights into the softening of elastic constants, with ourfittings confirming these trends.Future experiments will refine the understanding of these transitions, expanding measurements ofelastic constants and exploring scattering along additional directions. These efforts aim to advanceknowledge of the interplay between structural, acoustic, and magnetic properties in CuFe2O4.[1] T. Inoue and S. Iida. Specific heats of copper ferrite. J. Phys. Soc. Japan, 13, 1958.[2] J. B. Goodenough and A. L. Loeb. Specific heats of copper ferrite. Phys. Rev., 98:391,1955.[3] J. D. Dunitz and L. E. Orgel. Jahn-teller effect and the structure of copper ferrite.J. Phys. Chem. Solid., 3:20, 1957.[4] E. F. Bertaut. Structural transitions in cufe2o4. Compt. Rend., 230:213, 1950.[5] S. Miyahara and H. Ohnishi. The phase transition in cufe2o4 as observed by x-raydiffraction at high temperature. J. Phys. Soc. Japan, 12:1296, 1956.[6] T. Yasuda T. Takei and S. Ishihara. Anomalous behavior of magnetization in cufe2o4.Denkigakkai Shi in Japan, 59:568, 1939.[7] R. Baffle R. Forrer and P. Fourinier. Magnetic properties of copper ferrites. J. de Phys., 6:71,1945.
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