Phase transitions in BaMnF<sub>4</sub>

Scott, J. F.

doi:10.1088/0034-4885/42/6/003

Cited by 158 publications

(93 citation statements)

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“…9 Also, spin-phonon coupling that may lead to dielectric anomalies has been envisaged for geometrically frustrated ZnCr 2 O 4 spinel. 10 Multiferroicity in conventional spinel oxides has been predicted 11 and studied. However, the strength of magnetoelectric coupling was found to be weak.…”

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confidence: 99%

Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)

Rajeevan

Pradyumnan

Kumar

et al. 2008

Applied Physics Letters

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We present the structural, dielectric and magnetization study of single phase polycrystalline Bi x Co 2−x MnO 4 ͑0 ഛ x ഛ 0.3͒, synthesized by a conventional solid state route. All the samples have the cubic spinel structure with Fd3m space group. Bi-substitution in Co 2 MnO 4 stabilizes the ferroelectric transition at a temperature of ϳ350 K and enhances the dielectric constant with a relaxor behavior. The capacitance-voltage ͑C-V͒ measurements confirm the ferroelectric nature at room temperature. Ferrimagnetic nature of the Co 2 MnO 4 is preserved in the Bi-substituted samples. Magnetocapacitive coupling proves candidature of these materials from an application point of view. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2894518͔In multiferroic materials, magnetism and ferroelectricity ͑FE͒ coexist. These materials have attracted considerable attention in recent years. [1][2][3][4][5][6][7] The simultaneous occurrence of ferromagnetism/ferrimagnetism ͑FM͒ and FE and the coupling between these two order parameters could lead to the emergence of new storage media, which enable electrically reading/writing of the magnetic memories and vice versa, yielding more degrees of freedom from device application point of view. Multiferroics with coupled electrical and magnetic properties are termed as magnetoelectric multiferroics. However, there are only very few multiferroic materials with a sufficient amount of magnetoelectric coupling because of the contrasting origins of these properties. Among recently established magnetoelectric multiferroic materials, 8 frustrated magnets and geometrical frustration of lattice degrees of freedom have been found to be the leading mechanisms for perovskite manganites and cubic spinel systems, respectively. In this context, for FE and FM to coexist in single phase, the atom which moves off the center to induce the electric dipole moment should be different from those that carry the magnetic moment ͑atoms with partially filled d orbitals, responsible for FM͒. Recent ab initio calculations for existing ferroelectrics suggest that atoms with d 0 configuration create more off center distortion. 2,4 In principle, coexistence of FE and FM can be achieved through either an alternative mechanism like a non-d electron for magnetism or through an alternative mechanism for FE. In practice, alternative mechanisms for FE are pursued. 7 One such alternative followed is the induction of nonmagnetic ions having stereochemically active lone pair of electrons that may introduce off centering in the structure containing transition metal ions. 9 Also, spin-phonon coupling that may lead to dielectric anomalies has been envisaged for geometrically frustrated ZnCr 2 O 4 spinel. 10 Multiferroicity in conventional spinel oxides has been predicted 11 and studied. However, the strength of magnetoelectric coupling was found to be weak. 12 One can think of a way to engineer a new class of materials, combining the mechanisms discussed in previous paragraph to achieve multiferroicity in spinel materials. Inc...

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mentioning

confidence: 99%

Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)

Rajeevan

Pradyumnan

Kumar

et al. 2008

Applied Physics Letters

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“…However, the paraelectric -ferroelectric transition and its mechanism have been strongly evidenced by both experimental and theoretical studies [16,20,21,24]. There is also strong experimental evidence of the existence of the "soft" Raman bands which disappear at the Curie point [24,34].…”

Section: Analysis and Discussion Of Molecular Dynamics In Fluoridesmentioning

confidence: 99%

“…The low temperature studies have been predominantly focused on magnetic properties of BaMnF 4 and BaNiF 4 [12,15,22,23]. The incommensurate -commensurate phase transition, which occurs at 250 K has been observed and accepted only in BaMnF 4 [12,24]. Only recently, low temperature dynamics in BaZnF 4 and BaMn 1−x Zn x F 4 have been studied and analysed in more detail [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

“…Raman experiments were also mostly focused on the ferroelectric -paraelectric phase transition [12,34] and the incommensurate -commensurate phase transition in BaMnF 4 [24]. Detailed data over a wide range of temperatures have been published only for BaZnF 4 and there are reports of anomalous behaviour for some particular modes at 300 K [25].…”

Section: Introductionmentioning

confidence: 99%

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A variable temperature solid-state nuclear magnetic resonance, electron paramagnetic resonance and Raman scattering study of molecular dynamics in ferroelectric fluorides

Kowalczyk¹,

Kemp²,

Walker³

et al. 2011

J. Phys.: Condens. Matter

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The local nuclear and electronic structures and molecular dynamics of the ferroelectric lattice in selected geometric fluorides (BaMgF 4 , BaZnF 4 , BaMg 1−x Mn x F 4 and BaMg 1−x Ni x F 4 ; x = 0.001 and 0.005) have been investigated. The 19 F and 25 Mg isotropic chemical shift δ iso , 25 Mg quadrupolar coupling constants (C q ) and asymmetry parameters (η) reflect the geometry of the coordination spheres. The zero-field splitting parameters |D| and |E| are consistent with distorted axial symmetry (low temperatures) and nearly rhombic symmetry (high temperatures) of octahedral Mn 2+ coordination. The high resolution of the nuclear magnetic resonance, electron paramagnetic resonance and phonon spectra are consistent with the highly ordered crystallographic structure. Combined multi-technique data evidence the subtle discontinuous changes in the temperature dependences of |D| and |E|, isotropic chemical shifts δ iso and signature parameters of Raman bands and suggest a discontinuous structural distortion of the fluoride octahedra. The temperature at which this change occurs depends on the ionic radius of the central ion of the octahedral site and is estimated to be ∼300 K for Zn 2+ fluorides and ∼240 K for Mg 2+ fluorides. This geometrical distortion modifies the lattice dynamics and originates from the rotation of the fluoride octahedra around a new direction approximately perpendicular to that related to the paraelectric-ferroelectric phase transition.

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“…The lattice consists of layers of vertex-sharing MF 6 octahedra separated by layers of Ba atoms. The ferroelectric transitions are above the melting temperatures of the compounds, while antiferromagnetic ordering takes place below 70 K (see Scott 44 for a review).…”

Section: Bamfmentioning

confidence: 99%

Multiferroic Materials: Physics and Properties

Palstra

Blake

2016

Reference Module in Materials Science and Materials Engineering

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Multiferroics are materials in which magnetism and ferroelectricity coexist. They are of fundamental interest to understand electronic behavior coupling magnetic interactions and electric dipolar order. Moreover, they are of applied interest because they allow various types of novel magnetic and electric device structures. We distinguish two important classes of multiferroic materials and discuss mechanisms and materials belonging to each class separately. In the first group of multiferroics, magnetization and polarization arise independently from each other. In the second category of multiferroics, ferroelectricity is induced by magnetic order, resulting in strong magnetoelectric coupling. We also briefly discuss multiferroic thin film heterostructures showing interfacial magnetoelectric coupling interactions with potential applications in memory devices

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Phase transitions in BaMnF₄

Cited by 158 publications

References 68 publications

Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)

Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)

A variable temperature solid-state nuclear magnetic resonance, electron paramagnetic resonance and Raman scattering study of molecular dynamics in ferroelectric fluorides

Multiferroic Materials: Physics and Properties

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Phase transitions in BaMnF4

Cited by 158 publications

References 68 publications

Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)

Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)

A variable temperature solid-state nuclear magnetic resonance, electron paramagnetic resonance and Raman scattering study of molecular dynamics in ferroelectric fluorides

Multiferroic Materials: Physics and Properties

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Phase transitions in BaMnF₄