Magnetoelastic coupling and ferromagnetic-type in-gap spin excitations in multiferroic $\alpha$-Cu${}_2$V${}_2$O${}_7$

Abstract

We investigate magnetoelectric coupling and low-energy magnetic excitations in multiferroic $\alpha$-Cu${}_2$V${}_2$O${}_7$ by detailed thermal expansion, magnetostriction, specific heat and magnetization measurements in magnetic fields up to 15~T and by high-field/high-frequency electron spin resonance studies. Our data show negative thermal expansion in the temperature range $\le 200$~K under study. Well-developed anomalies associated with the onset of multiferroic order (canted antiferromagnetism with a significant magnetic moment and ferroelectricity) imply pronounced coupling to the structure. We detect anomalous entropy changes in the temperature regime up to $\sim 80$~K which significantly exceed the spin entropy. Failure of Grüneisen scaling further confirms that several dominant ordering phenomena are concomitantly driving the multiferroic order. By applying external magnetic fields, anomalies in the thermal expansion and in the magnetization are separated. Noteworthy, the data clearly imply the development of a canted magnetic moment at temperatures above the structural anomaly. Low-field magnetostriction supports the scenario of exchange-striction driven multiferroicity. We observe low-energy magnetic excitations well below the antiferromagnetic gap, i.e., a ferromagnetic-type resonance branch associated with the canted magnetic moment arising from Dzyaloshinsii-Moriya interactions. The anisotropy parameter $\tilde{D}=1.6(1)$~meV indicates a sizeable ratio of DM- and isotropic magnetic exchange.

References in corpus (14)

• Multiferroicity, The coupling between magnetic and polarization
• Multiferroicity due to charge ordering
• beta-Cu2V2O7: a spin-1/2 honeycomb lattice system
• Nonreciprocal magnons and symmetry-breaking in the noncentrosymmetric antiferromagnet
• Magnetodielectric and magnetoelastic coupling in TbFe3(BO3)4
• Magnetic structure and Dzyaloshinskii-Moriya interaction in the $S=1/2$ helical-honeycomb antiferromagnet $\alpha$-Cu${}_2$V${}_2$O${}_7$
• Exchange striction induced giant ferroelectric polarization in copper based multiferroic material $\alpha$-Cu${}_2$V${}_2$O${}_7$
• Low energy magnetic excitations in the spin-orbital Mott insulator Sr${}_2$IrO${}_4$
• Revisiting the chain magnetism in Sr14Cu24O41: Experimental and numerical results
• High-field magnetization and magnetic phase diagram of $\alpha$-Cu${}_2$V${}_2$O${}_7$
• Non-Resonant X-ray Magnetic Scattering on Rare-Earth Iron Borates RFe${}_3$(BO${}_3$)${}_4$
• Magneto-elastic couplings in the distorted diamond-chain compound azurite
• Spin wave excitations in the pyrovanadate alpha-Cu2V2O7
• Pr magnetism and its interplay with the Fe spin density wave in PrFeAsO

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