Multiple phase transitions in CuO observed with thermal expansion

Rebello, A.; Winter, Zachary; Viall, S.; Neumeier, J. J.

doi:10.1103/physrevb.88.094420

Cited by 16 publications

(28 citation statements)

References 42 publications

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“…It exists in a narrow temperature range of less than 1 degree right above T N2 (ref. 18 ), as also indicated by recent thermal-expansion measurements 23 . Such a phase was not reproduced in the earlier theoretical studies 24 25 26 .…”

supporting

confidence: 77%

Magnetoelectric effect and phase transitions in CuO in external magnetic fields

et al. 2016

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Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of ≈50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions.

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confidence: 77%

Magnetoelectric effect and phase transitions in CuO in external magnetic fields

et al. 2016

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“…Change in the CuO thickness with temperature is set in the optical model according to expansion coefficients reported in ref. 36 θ is fixed in the analysis for all temperatures as it does not depend on ϕ , temperature, or any other experimental variables. Values of ϕ for each azimuth orientation measured through the cryostat are determined by applying the optical model for outside the cryostat.…”

Section: Methodsmentioning

confidence: 99%

Electromagnon excitation in cupric oxide measured by Fabry-Pérot enhanced terahertz Mueller matrix ellipsometry

Knight

Prabhakaran

Binek

et al. 2019

Sci Rep

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Here we present the use of Fabry-Pérot enhanced terahertz (THz) Mueller matrix ellipsometry to measure an electromagnon excitation in monoclinic cupric oxide (CuO). As a magnetically induced ferroelectric multiferroic, CuO exhibits coupling between electric and magnetic order. This gives rise to special quasiparticle excitations at THz frequencies called electromagnons. In order to measure the electromagnons in CuO, we exploit single-crystal CuO as a THz Fabry-Pérot cavity to resonantly enhance the excitation’s signature. This enhancement technique enables the complex index of refraction to be extracted. We observe a peak in the absorption coefficient near 0.705 THz and 215 K, which corresponds to the electromagnon excitation. This absorption peak is observed along only one major polarizability axis in the monoclinic a–c plane. We show the excitation can be represented using the Lorentz oscillator model, and discuss how these Lorentz parameters evolve with temperature. Our findings are in excellent agreement with previous characterizations by THz time-domain spectroscopy (THz-TDS), which demonstrates the validity of this enhancement technique.

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“…Each curve presented herein is composed of about 1800 data points, with a spacing of 0.2 K. The data for the linear thermal expansion were fitted using a method described previously 26 prior to calculating the thermal expansion coefficient. Thermal expansion data for the two crystals agree well.…”

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Local and long-range magnetic order of thespin−32systemCoSb2O6

et al. 2015

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The Co 2+ ions of CoSb2O6 exhibit local magnetic order below ∼80 K followed by long-range antiferromagnetic order below TN = 13.45 K. Analysis of the magnetic susceptibility above TN using an Ising model of Co-Co dimers, yields a magnetic exchange coupling J /kB = −10.603(6) K (kB is the Boltzmann constant). The transition at TN is accompanied by a spin gap in the heat capacity (∆2/kB = 33.92(9) K). Highly anisotropic behavior of the thermal expansion is observed, and the influence of local magnetic order is evident. A critical exponent of α = 0.103(3) is obtained from analysis of the critical behavior of the heat capacity and thermal expansion near TN , similar to the value expected for the three dimensional Ising universality class.

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Multiple phase transitions in CuO observed with thermal expansion

Cited by 16 publications

References 42 publications

Magnetoelectric effect and phase transitions in CuO in external magnetic fields

Magnetoelectric effect and phase transitions in CuO in external magnetic fields

Electromagnon excitation in cupric oxide measured by Fabry-Pérot enhanced terahertz Mueller matrix ellipsometry

Local and long-range magnetic order of thespin−32systemCoSb2O6

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