Magnetodielectric effects in A-site cation-ordered chromate spinels LiMCr4O8 (M=Ga and In)

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American Physical Society
We report the occurrence of a magnetodielectric effect and its correlation with structure and magnetism in the A-site ordered chromate spinel oxides LiMCr4O8 (M=Ga, In). In addition to magnetic and dielectric measurements, temperature dependent synchrotron and neutron diffraction experiments have been carried out for the Ga compound. The results are compared and contrasted with that of a corresponding conventional B-site magnetic chromate spinel oxide, ZnCr2O4. Like ZnCr2O4, the A-site ordered chromate spinels exhibit a magnetodielectric effect at the magnetic ordering temperature (TN∼13–15K), resulting from magnetoelastic coupling through a spin Jahn-Teller effect. While the presence of a broad magnetic anomaly, associated with a short-range magnetic ordering (TSO∼45K) in ZnCr2O4, does not cause any dielectric anomaly, a sharp change in dielectric constant has been observed in LiInCr4O8 at the magnetic anomaly, which is associated with the opening of a spin gap (TSG∼60K). Contrary to the In compound, a broad dielectric anomaly exists at the onset of short-range antiferromagnetic ordering (TSO∼55K) in LiGaCr4O8. The differences in dielectric behavior of these compounds have been discussed in terms of breathing distortion of the Cr4 tetrahedra. ©2016 American Physical Society
Antiferromagnetism, Dielectric properties, Magnetism, L-S coupling, Cations, Jahn-Teller effect, Neutron diffraction
Saha, R., Fauth, F., Avdeev, M., Kayser, P., Kennedy, B. J., & Sundaresan, A. (2016). Magnetodielectric effects in A-site cation-ordered chromate spinels LiMCr4O8 (M=Ga and In). Physical Review B, 94(6), 064420. doi:10.1103/PhysRevB.94.064420