Magnetic excitations and anomalous spin-wave broadening in multiferroic FeV2O4

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2014-06-01
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Zhang, Qiang
Ramazanoglu, Mehmet
Chi, Songxue
Liu, Yong
Lograsso, Thomas
Vaknin, David
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Lograsso, Thomas
Ames Laboratory Division Director
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Ames National Laboratory

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We report on the different roles of two orbital-active Fe2+ at the A site and V3+ at the B site in the magnetic excitations and on the anomalous spin-wave broadening in FeV2O4. FeV2O4 exhibits three structural transitions and successive paramagnetic (PM)–collinear ferrimagnetic (CFI)–noncollinear ferrimagnetic (NCFI)/ferroelectric transitions. The high-temperature tetragonal/PM–orthorhombic/CFI transition is accompanied by the appearance of a large energy gap in the magnetic excitations due to strong spin-orbit-coupling-induced anisotropy at the Fe2+ site. While there is no measurable increase in the energy gap from the orbital ordering of V3+ at the orthorhombic/CFI–tetragonal/NCFI transition, anomalous spin-wave broadening is observed in the orthorhombic/CFI state due to V3+ spin fluctuations at the B site. The spin-wave broadening is also observed at the zone boundary without softening in the NCFI/ferroelectric phase, which is discussed in terms of magnon-phonon coupling. Our study also indicates that the Fe2+ spins without the frustration at the A site may not play an important role in inducing ferroelectricity in the tetragonal/NCFI phase of FeV2O4.

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This article is from Physical Review B 89 (2014): 224416, doi:10.1103/PhysRevB.89.224416. Posted with permission.

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Wed Jan 01 00:00:00 UTC 2014
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