Coupled phonons, magnetic excitations, and ferroelectricity in AlFeO3: Raman and first-principles studies

Kumar, Pradeep and Bera, Achintya and Muthu, DVS and Shirodkar, Sharmila N and Saha, Rana and Shireen, Ajmala and Sundaresan, A. and Waghmare, UV and Sood, AK and Rao, CNR (2012) Coupled phonons, magnetic excitations, and ferroelectricity in AlFeO3: Raman and first-principles studies. In: PHYSICAL REVIEW B, 85 (13).

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Abstract

We determine the nature of coupled phonons and magnetic excitations in AlFeO3 using inelastic light scattering from 5 to 315 K covering a spectral range from 100 to 2200 cm(-1) and complementary first-principles density functional theory-based calculations. A strong spin-phonon coupling and magnetic ordering-induced phonon renormalization are evident in (1) anomalous temperature dependence of many modes with frequencies below 850 cm(-1), particularly near the magnetic transition temperature T-c approximate to 250 K, and (2) distinct changes in band positions of high-frequency Raman bands between 1100 and 1800 cm(-1); in particular, a broad mode near 1250 cm(-1) appears only below T-c, attributed to the two-magnon Raman scattering. We also observe weak anomalies in the mode frequencies similar to 100 K due to a magnetically driven ferroelectric phase transition. Understanding of these experimental observations has been possible on the basis of first-principles calculations of the phonons' spectrum and their coupling with spins.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW B
Publisher:	PHYSICAL REVIEW B
Additional Information:	Copyright for this article belongs to American Physical Society
Keywords:	SCATTERING;MULTIFERROICS;MAGNONS
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	10 Jul 2012 07:21
Last Modified:	10 Jul 2012 07:24
URI:	http://eprints.iisc.ac.in/id/eprint/44602

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