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Abstract Spinel compounds are of great interest in both fundamental and application-oriented perspectives due to the geometric magnetic frustration inherent to their lattice and the resulting complex magnetic states. Here, we applied x-ray diffraction, magnetization, heat capacity and powder inelastic neutron scattering measurements, along with theoretical calculations, to study the exotic properties of chromite-spinel oxides CoCr2O4and MnCr2O4. The temperature dependence of the phonon spectra provides an insight into the correlation between oxygen motion and the magnetic order, as well as the magnetoelectric effect in the ground state of MnCr2O4. Moreover, spin-wave excitations in CoCr2O4and MnCr2O4are compared with Heisenberg model calculations. This approach enables the precise determination of exchange energies and offers a comprehensive understanding of the spin dynamics and relevant exchange interactions in complicated spiral spin ordering.
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Impact of thermal annealing on magnetic properties in the nanostructured compositionally complex spinel cobaltites (Mg0.2Mn0.2Fe0.2Cu0.2Zn0.2)Co2O4
Exploring the controllable aspects of local atomic structure and chemical ordering and their correlations with functional properties is crucial for harnessing the potential of complex oxides in the development of advanced materials. In this work, we have investigated the sensitivity of the magnetic properties in a nanostructured metastable spinel compositionally complex oxide (CCO) composition, (Mg0.2Mn0.2Fe0.2Cu0.2Zn0.2)Co2O4, to local chemical segregation and phase evolution introduced through variation in post-processing heat treatment temperature. A combination of x-ray diffraction, scanning transmission electron microscopy with energy dispersive x-ray spectroscopy, first-order reversal curve (FORC) magnetometry, and neutron diffraction and total scattering analyses was employed to understand both average and local structure-property evolution. Structure analysis shows that the postannealing process triggers local and long-range cation diffusion, resulting in changes in the distribution of atoms residing on the tetrahedral and octahedral sites of the spinel structure as well as nanoscale chemical heterogeneity. FORC analysis shows that redistribution of magnetic cations induces subtle magnetic phase separation and soft to hard magnetic phase transformations, and demonstrates incipient demixing of the as-synthesized material well before detection by neutron total scattering. This work additionally highlights the necessity of a combination of advanced characterization techniques for understanding the broader crystal-chemical class of compositionally complex oxides.
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- Award ID(s):
- 2145174
- PAR ID:
- 10674391
- Publisher / Repository:
- American Physical Soceity
- Date Published:
- Journal Name:
- Physical Review B
- Volume:
- 112
- Issue:
- 18
- ISSN:
- 2469-9950
- Subject(s) / Keyword(s):
- Magnetism Structural properties Oxides Spinels Magnetic moment Annealing Electron microscopy Magnetization measurements Neutron diffraction Neutron pair-distribution function analysis
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1103/87mk-gdfg
