Single crystal growth of LuFe2O4, LuFeCoO4 and YbFeMgO4 by the floating zone method

Iida, Junji; Takekawa, Shunji; Kimizuka, Noboru

doi:10.1016/0022-0248(90)90397-4

Cited by 41 publications

(22 citation statements)

References 4 publications

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“…25. Starting materials of Lu 2 O 3 and Fe 2 O 3 with 99.99% purity were mixed, pressed into pellets, and sintered at 1200 • C during 6 h in H 2 /He/CO 2 atmosphere (H 2 /CO 2 ratio 1/3) and quenched into ice water.…”

Section: Methodsmentioning

confidence: 99%

Intrinsic electrical properties of LuFe2O4

et al. 2013

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We here revisit the electrical properties of LuFe 2 O 4 , compound candidate for exhibiting multiferroicity. Measurements of dc electrical resistivity as a function of temperature, electric-field polarization measurements at low temperatures with and without magnetic field, and complex impedance as a function of both frequency and temperature were carried out in a LuFe 2 O 4 single crystal, perpendicular and parallel to the hexagonal c axis, and in several ceramic polycrystalline samples. Resistivity measurements reveal that this material is a highly anisotropic semiconductor, being about two orders of magnitude more resistive along the c axis. The temperature dependence of the resistivity indicates a change in the conduction mechanism at T CO ≈ 320 K from thermal activation above T CO to variable range hopping below T CO . The resistivity values at room temperature are relatively small and are below 5000 cm for all samples but we carried out polarization measurements at sufficiently low temperatures, showing that electric-field polarization curves are a straight line as expected for a paraelectric or antiferroelectric material. Furthermore, no differences are found in the polarization curves when a magnetic field is applied either parallel or perpendicular to the electric field. The analysis of the complex impedance data corroborates that the claimed colossal dielectric constant is a spurious effect mainly derived from the capacitance of the electrical contacts. Therefore, our data unequivocally evidence that LuFe 2 O 4 is not ferroelectric.

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Section: Methodsmentioning

confidence: 99%

Intrinsic electrical properties of LuFe2O4

et al. 2013

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“…The magnetic structure is refined with a ferrimagnetic spin configuration with a propagation vector of (1/3 1/3 0). The magnetic intensity appearing on peaks where L is a 1/2-integer is a consequence of the charge ordering at ∼320 K. In addition, evidence is presented for a second transition at 175 K with significant changes in magnetic peak intensities and broadening of many reflections.Single crystals of LuFe 2 O 4 were grown by floatingzone-melting, using an oxygen partial pressure tuned by a CO/CO 2 mixture to control oxygen stoichiometry [10]. For CO/CO 2 ratio close to 2.7 the magnetic behavior exhibits two sharp magnetic transitions in contrast to previous single crystal magnetization measurements [9] which show only a single transition.…”

mentioning

confidence: 97%

“…Single crystals of LuFe 2 O 4 were grown by floatingzone-melting, using an oxygen partial pressure tuned by a CO/CO 2 mixture to control oxygen stoichiometry [10]. For CO/CO 2 ratio close to 2.7 the magnetic behavior exhibits two sharp magnetic transitions in contrast to previous single crystal magnetization measurements [9] which show only a single transition.…”

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confidence: 97%

Three-Dimensional Magnetic Correlations in MultiferroicLuFe2O4

et al. 2008

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We present single crystal neutron diffraction measurements on multiferroic LuFe2O4. Magnetic reflections are observed below transitions at 240 and 175 K indicating that the magnetic interactions in LuFe2O4 are 3-dimensional (3D) in character. The magnetic structure is refined as a ferrimagnetic spin configuration below the 240 K transition. Below 175 K a significant broadening of the magnetic peaks is observed along with the build up of a diffuse component to the magnetic scattering. 75.30.Kz, 28.20.Cz, 25.40.Dn Materials that offer the possibility of simultaneously controlling magnetic and electric degrees of freedom are the subject of intense interest [1]. Recently, multiferroic materials have been identified that show large coupling between electric and magnetic degrees of freedom. Ferroelectricity driven by either magnetic or charge ordering appears to be the origin of the large coupling and, hence, understanding the underlying electronic interactions is crucial for further insight into multiferroicity [1].LuFe 2 O 4 has attracted attention as a novel ferroelectric material where ferroelectricity is driven by the electronic process of charge ordering of Fe 2+ and Fe 3+ ions and for indications of coupling between electronic and magnetic degrees of freedom [2,3,4,5,6]. LuFe 2 O 4 is a member of the RFe 2 O 4 (R = rare earth element) family, the physical properties of which depend strongly on oxygen stoichiometry. For example, nearly stoichiometric YFe 2 O 4 exhibits three-dimensional (3D) magnetic order while oxygen deficient YFe 2 O 4 exhibits two-dimensional (2D) magnetic order [7]. LuFe 2 O 4 exhibits multiple phase transitions. 2D charge correlations are observed below 500 K, while below 320 K 3D charge order is established, roughly coinciding with the onset of ferroelectricity [2,8]. Magnetic order appears below 240 K and 2D ferrimagnetic order has been suggested by neutron scattering studies [9]. However, strong sample dependent behavior observed in other members of RFe 2 O 4 [7] suggests that unraveling the interesting behavior of LuFe 2 O 4 requires paying due attention to sample quality.In this letter we present extensive neutron diffraction measurements from 20 to 300 K on high quality single crystals of LuFe 2 O 4 . We report several new findings that provide information about the underlying magnetic interactions. First, our measurements indicate that below 240 K 3D magnetic correlations exist with magnetic intensity appearing at (1/3 1/3 L) where L may take on integer and 1/2-integer values. The magnetic structure is refined with a ferrimagnetic spin configuration with a propagation vector of (1/3 1/3 0). The magnetic intensity appearing on peaks where L is a 1/2-integer is a consequence of the charge ordering at ∼320 K. In addition, evidence is presented for a second transition at 175 K with significant changes in magnetic peak intensities and broadening of many reflections.Single crystals of LuFe 2 O 4 were grown by floatingzone-melting, using an oxygen partial pressure tuned by a CO/CO 2 mi...

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“…High-quality single crystals were grown using a four-mirror floating zone furnace, as described elsewhere. 24 Core levels and valence band were recorded by means of XPS, using a PHI5600ci multitechnique spectrometer with monochromatic Al K␣ radiation with an overall resolution of about 0.3 eV. The XMCD, XAS, and XES measurements were performed at beamlines 4.0.2 and 8.0.1 at the Advanced Light Source in Berkeley, California.…”

mentioning

confidence: 99%

Charge order, enhanced orbital moment, and absence of magnetic frustration in layered multiferroicLuFe2O4

et al. 2009

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Electronic and magnetic properties of the charge ordered phase of LuFe 2 O 4 are investigated by means of x-ray spectroscopic and theoretical electronic structure approaches. LuFe 2 O 4 is a compound showing fascinating magnetoelectric coupling via charge ordering. Here, we identify the spin ground state of LuFe 2 O 4 in the charge ordered phase to be a 2:1 ferrimagnetic configuration, ruling out a frustrated magnetic state. An enhanced orbital moment may enhance the magnetoelectric coupling. Furthermore, we determine the densities of states and the corresponding correlation potentials by means of x-ray photoelectron and emission spectroscopies, as well as electronic structure calculations. DOI: 10.1103/PhysRevB.80.220409 PACS number͑s͒: 75.80.ϩq, 71.20.Ϫb, 78.70.Dm, 78.70.En Multiferroic transition metal oxides, i.e., compounds in which more than one ferroic phase coexist, have gained enormous attention during the last few years. 1-4 Besides a number of perovskites and related compounds, 2,5,6 the charge frustrated layered compound LuFe 2 O 4 has attracted intense interest due to its fascinating ferroelectric and magnetoelectric properties. 7,8 LuFe 2 O 4 has a rhombohedral crystal structure ͑space group R3m͒. The underlying layered structure consists of W-like hexagonal Fe 2 O 2.5 and U-like LuO 1.5 layers. 9 The W layers comprise two triangular nets of Fe ions; the resulting electric polarization is induced via a frustrated charge ordering of Fe 2+ and Fe 3+ ions on the resulting honeycomb lattice below 330 K. [10][11][12] Below 240 K a longrange ferrimagnetic order sets in. 7 The fact that the ferroelectricity is caused by correlated electrons from the Fe ions leads to unusual properties and unique capabilities of LuFe 2 O 4 . A large response of the dielectric constant by applying small magnetic fields has been found, opening a possible route for future devices. 8 Phase transitions from the charge ordered ͑CO͒ phase have been very recently associated with a nonlinear current-voltage behavior and an electric-field-induced phase transition, which might be of interest for potential electric-pulse-induced resistive switching applications. 13,14 The large magnetoelectric coupling has been attributed to an intricate interplay between charge and spin degrees of freedom with the crystal lattice and external electrical and magnetic fields to some extent on a short-range order. [15][16][17][18][19] However, there is still some confusion about the nature of spin-charge coupling in LuFe 2 O 4 . In particular a model finding a ͱ 3 ϫ ͱ 3 CO ground state 20,21 is challenged by simulations implying that the electrical polarization in LuFe 2 O 4 is due to spin-charge coupling and a spin frustrated magnetic ground state in a chain CO state. 22,23 On the other hand the first model finds a ferrimagnetic spin ground state where Fe 2+ and 1/3 of Fe 3+ make up the majority spin, and 2/3 of Fe 3+ make up the minority spin.X-ray magnetic circular dichroism ͑XMCD͒ is a very powerful tool to investigate the internal magnetic stru...

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Single crystal growth of LuFe2O4, LuFeCoO4 and YbFeMgO4 by the floating zone method

Cited by 41 publications

References 4 publications

Intrinsic electrical properties of LuFe2O4

Intrinsic electrical properties of LuFe2O4

Three-Dimensional Magnetic Correlations in MultiferroicLuFe2O4

Charge order, enhanced orbital moment, and absence of magnetic frustration in layered multiferroicLuFe2O4

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