MAGNETOELECTRIC EFFECTS IN MULTIFERROICS

2021 ◽  
Vol 0 (1) ◽  
pp. 44-48
Author(s):  
Z.V. GAREEVA ◽  
◽  
E.I. BADERTDINOVA ◽  
Keyword(s):  
Rare Earth ◽  
Single Phase ◽  
Bismuth Ferrite ◽  
Theoretical Research ◽  
Essential Difference ◽  
Magnetoelectric Effects ◽  
Space Group ◽  
Magnetoelectric Properties ◽  
Symmetry Space ◽  
Symmetry Space Group

Research of magnetoelectric effects and multiferroic materials, in which these effects are manifested, is among key areas in modern magnetism. This is associated with promising aspects of applying the results to spintronics, orbitronics, and new generation systems for information storage and processing. Despite a great many of already known materials which, in varying degrees, have magnetoelectric properties, the question regarding physical mechanisms and nature of magnetoelectric effects still remains open. Single-phase multiferroics with their magnetic and segnetoelectric properties implemented in a single crystalline phase are of especially great interest for studying. The most known "traditional multiferroics", such as bismuth ferrite, manganites, rare earthearth orthoferrites and orthochromites, fall into the class of perovskite multiferroics, i.e. the crystalline structure of ABO3 perovskites serve as their pre-phase. However, the difference between crystallographic distortions that results in the formation of various crystalline structures, for example, bismuth ferrite and rare-earth orthoferrites/orthochromites, leads to an essential difference in their physical properties, including magnetoelectric ones. Whereas bismuth ferrite characterized by the R3c symmetry space group is a segnetoelectric (i.e. it has spontaneous segnetoelectric polarization), the presence of segnetoelectric polarization in orthoferrites/orthochromites with the Pbnm symmetry space group is impossible from the symmetry standpoint. However, recent experimental and theoretical research works show that under certain conditions magnetoelectric properties are found in both classes of the said multiferroics. This paper is an overview by its nature and discusses magnetoelectric effects in various classes of single-phase multiferroics with the distorted perovskite structure: proper multiferroics exemplified by bismuth ferrite and improper multiferroics exemplified by rare-earth orthoferrites/orthochromites. Consideration is given to basic principles of the symmetry approach used to study magnetoelectric effects in multiferroics; calculations and analysis of magnetoelectric effects in rare-earth orthoferrites/orthochromites are performed through the methods of group-theoretical analysis.

Elektroneutrale Pb4O4 -Heterokubaneinheiten in den Aluminatsodalithen Ln4[Al12O24](Pb4O4)2 (Ln = Nd, Sm) / Electrically Neutral Pb4O4 Heterocubane Units in Aluminate Sodalites Ln4[Al12O24](Pb4O4)2 (Ln = Nd, Sm)

1997 ◽  
Vol 52 (4) ◽  
pp. 449-452 ◽  
Author(s):  
J.-P. Werner ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Single Crystals ◽  
Rare Earth Ions ◽  
Neutral Network ◽  
Cubic Symmetry ◽  
Space Group ◽  
Coordination Spheres ◽  
Symmetry Space ◽  
Symmetry Space Group

Abstract Single crystals of Ln4[Al12O24](Pb4O4)2 (Ln = Nd, Sm) have been prepared by flux techniques. The compounds crystallize with cubic symmetry, space group Oh-Pn3̄m, aNd = 9.514(1), aSm = 9.481(1) Å, Z = 1. The crystal structure is characterized by a [Al12O24]12- framework. Four of the eight six-membered rings of AlO4-tetrahedra per sodalite cage are centered by Ln3+ ions. The cages of the resulting electrically neutral network are filled with [Pb4O4]±0 heterocubane units. Oxygen of the heterocubane units completes the coordination spheres of the rare earth ions to hexagonal bipyramids.

scholarly journals Zur Kristallchemie von CuDyMo2O8 und CuYbMo2O8

1996 ◽  
Vol 51 (2) ◽  
pp. 240-244
Author(s):  
Hk. Müller-Buschbaum ◽  
St. Gallinat
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Single Crystals ◽  
Rare Earth Ions ◽  
Orthorhombic Symmetry ◽  
Space Group ◽  
Group D ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
The Rare Earth

Abstract Single crystals of (I) CuDyMo2O8 and (II) CuYbMo2O8 have been prepared by crystalli­sation from melts. Both com pounds crystallize with orthorhombic symmetry, space group D152h-Pbca with (I): a = 10.195(1), b = 9.721(2), c = 14.563(3); (II): a = 10.094(6), b = 9.628(9), c = 14.467(8) Å, Z = 8. The crystal structure is characterized by a triangular CuO3-polygon, a square antiprismatic coordination around the Rare Earth ions and the typical Mo O4 tetra­ hedra.

Synthese und Kristallstruktur von Pb2LnAl3O8 (Ln = Eu, Gd) / Synthesis and Crystal Structure of Pb2LnAl3O8 (Ln = Eu, Gd)

1996 ◽  
Vol 51 (6) ◽  
pp. 883-887 ◽  
Author(s):  
J.-P. Werner ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Single Crystals ◽  
Rare Earth Ions ◽  
Synthesis And Crystal Structure ◽  
Cubic Symmetry ◽  
Space Group ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
The Rare Earth

Abstract Single Crystals of Pb2LnAl3O8 (Ln = Eu, Gd) have been prepared by flux techniques. The compounds crystallize with cubic symmetry, space group Oh-Pn3̅m, a(Eu) = 9.4578(5), a(Gd) = 9.4448(7) Å, Z = 4. The crystal structure is characterized by heterocubane units of the type Pb4O4 and hexagonal bipyramids of oxygen around the rare earth ions. These components form a network made of macro polyhedra of the type Pb4O4- LnO6- Pb4O4

Zur Kenntnis eines Barium-Lanthanoid-Aluminat-Zinkats: BaLuAlZn3O7 mit einem Anhang zu Ba2Er2Zn8O13/On a Barium Rare Earth Aluminate Zincate: BaLuAlZn3O7 with a Note on Ba2Er2Zn8O13

1996 ◽  
Vol 51 (3) ◽  
pp. 343-347 ◽  
Author(s):  
Ch. Rabbow ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Oxygen Atom ◽  
Oxygen Content ◽  
Hexagonal Symmetry ◽  
Space Group ◽  
Symmetry Space ◽  
Symmetry Space Group

Abstract Reactions of BaCO3, ZnO, Lu2O3 and Al2O3 mixtures at temperatures up to 1500 °C led to small and colourless rods of BaLuAlZn3O7. The new compound crystallizes with hexagonal symmetry, space group C6v4 -P63mc, a = 6.273, c =10.161 Å, Z = 2. In spite of small differences in the oxygen content BaLuAlZn3O7 is isotypic to Ba2Ln2Zn8O13. The crystal structure shows Zn2+ with tetrahedral, Lu3+ with octahedral and Ba2+ with anticuboctahedral coordination by O2-. It has been shown that parts of the [Zn3AlO7]5- network are fragments of the ZnO structure. In consequence one oxygen atom is fourfold coordinated by zinc/aluminium. The space group of Ba2Ln2Zn8O13 must be corrected to C6v4 -P63mc.

Eine synthetische Spezies zum Mineral Howardevansit mit Eisen anstelle von Kupfer: NaFe3V3O12 / A Synthetic Species of the Mineral Howardevansite with Copper Displacing Iron: NaFe3V3O12

1995 ◽  
Vol 50 (1) ◽  
pp. 51-55 ◽  
Author(s):  
F.-D. Martin ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Solid State ◽  
Melting Point ◽  
Single Crystals ◽  
Crystal Chemistry ◽  
Solid State Reaction ◽  
Space Group ◽  
Triclinic Symmetry ◽  
Symmetry Space ◽  
Symmetry Space Group

Single crystals of NaFe3V3O12 have been prepared by solid state reaction below the melting point of the reaction mixture. This compound is isotypic to the mineral Howardevansite but shows lower triclinic symmetry, space group C11–P1, a = 6.757(2), b = 8.155(2), c = 9.816(3) Å, α = 106.05(2), β = 104.401(9), γ = 102.09(2)°, Z = 2. The acentric space group is caused by the sodium positions, all other atoms comply with the space group P̄ of Howardevansite. The different ions are coordinated by O2- forming VO4 tetrahedra, FeO6 octahedra, trigonal FeO5 bipyramids and irregular NaO5 and NaO7 polyhedra, respectively. The crystal chemistry is discussed with respect to Howardevansite.

scholarly journals Low-Temperature Ordering in the Cluster Compound (Bi8)Tl[AlCl4]3

Inorganics ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 45 ◽  
Author(s):  
Maximilian Knies ◽  
Martin Kaiser ◽  
Mai Lê Anh ◽  
Anastasia Efimova ◽  
Thomas Doert ◽  
...  
Keyword(s):  
Cluster Compound ◽  
Structure Model ◽  
X Ray Diffraction ◽  
Hexagonal Symmetry ◽  
Threefold Axis ◽  
Space Group ◽  
X Ray ◽  
A Chain ◽  
Symmetry Space ◽  
Symmetry Space Group

The reaction of Bi, BiCl3, and TlCl in the ionic liquid [BMIm]Cl·4AlCl3 (BMIm = 1-n-butyl-3-methylimidazolium) at 180 °C yielded air-sensitive black crystals of (Bi8)Tl[AlCl4]3. X-ray diffraction on single crystals at room temperature revealed a structure containing [ Tl ( AlCl 4 ) 3 ] ∞ 1 2 − strands separated by isolated Bi82+ square antiprisms. The thallium(I) ion is coordinated by twelve Cl− ions of six [AlCl4]− groups, resulting in a chain of face-sharing [TlCl12]11− icosahedra. The Bi82+ polycation is disordered, simulating a threefold axis through its center and overall hexagonal symmetry (space group P63/m). Slowly cooling the crystals to 170 K resulted in increased order in the Bi8 cluster orientations. An ordered structure model in a supercell with a’ = 2a, b’ = 2b, c’ = 3c and the space group P65 was refined. The structure resembles a hexagonal perovskite, with complex groups in place of simple ions.

Geordnete Metallverteilung in KBaVO4 und KSrVO4 mit β-K2SO4-Struktur / Ordered Metal Distribution in KBaVO4and KSrVO4 Showing β -K2SO4 Structure

1996 ◽  
Vol 51 (4) ◽  
pp. 477-480 ◽  
Author(s):  
O. Schrandt ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Single Crystals ◽  
Lattice Energy ◽  
Metal Distribution ◽  
Orthorhombic Symmetry ◽  
Space Group ◽  
Group D ◽  
Symmetry Space ◽  
Symmetry Space Group

Abstract Single crystals of KBaVO4(I) and KSrVO4(II) have been prepared by crystallization from V2O5 flux. The yellowish crystals show orthorhombic symmetry, space group D162h-Pnma with (I): a = 7.774(2), b = 5.899(1), c = 10.375(2) Å , (II): a = 7.400(2), b = 5.812(1), c -9.961(1), Z = 4. Both compounds show an ordered distribution of K+ and Ba2+ and Sr2+ respectively. The different sizes of the KO10 and BaO9 (SrO9) polyhedra are discussed with respect to those of the β-K2SO4 structure, considering the calculations of the Coulomb terms of lattice energy.

Crystal structure determination for crystals with twinning by hemihedry or pseudohemihedry

1991 ◽  
Vol 194 (3-4) ◽  
Author(s):  
Takaharu Araki
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Structure Determination ◽  
Difficult Case ◽  
Proper Selection ◽  
Space Group ◽  
Geometrical Symmetry ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
Selection Of

AbstractAn approach to structure determination for a crystal from component crystals in equal volume fractions, the most difficult case to the solution, is outlined with precautions for stepwise initialization. Proper selection of a crystal geometrical symmetry space group from a corresponding twin anti-symmetry space group and interpretation of a Patterson space are indispensable prerequisite for the solution. Observations unique to the case are briefly described in a sequence of Patterson synthesis, Fourier approach and least-squares refinement for efficient interpretation and processing.

A New Copper (II) Complex with the N,N'-Bis(antipyryl-4-methyl)-piperazine (BAMP) Ligand: [Cu(BAMP)](ClO4)2

2002 ◽  
Vol 57 (12) ◽  
pp. 1454-1460 ◽  
Author(s):  
Otilia Costișor ◽  
Ramona Tudose ◽  
Ingo Pantenburg ◽  
Gerd Meyer
Keyword(s):  
Crystal Structure ◽  
Copper Complex ◽  
Structural Parameters ◽  
Complex Molecule ◽  
Lattice Parameters ◽  
Tetragonal Symmetry ◽  
Apical Position ◽  
Space Group ◽  
Symmetry Space ◽  
Symmetry Space Group

The synthesis of the Mannich base N,N’-bis(antipyryl-4-methyl)-piperazine (BAMP) (1), its crystal structure as well as the synthesis and the crystal structure of the copper complex Cu(BAMP)(ClO4)2 (2) are reported. C28H34N6O2 ∙ 4H2O (BAMP ∙ 4H2O) crystallizes with triclinic symmetry, space group P1̄, lattice parameters: a = 704,9(2), b = 983,4(2), c = 1198,9(3) pm, α = 68,72°, β = 73,62°, γ = 78,49°. The copper-complex Cu(BAMP)(ClO4)2 crystallizes with tetragonal symmetry, space group P42/n, lattice parameters: a = 2295,1(3), c = 1412,2(2) pm. The copper(II) atom is five-coordinate by the two nitrogen atoms belonging to the piperazine ring and the oxygen atoms of the antipyrinemoieties. The geometry of the copper(II) atom can be described as a square-based pyramid with the N2O2 donor atoms of BAMP forming the basal plane and an oxygen atom of the neighbouring complex molecule occupying the apical position. BAMP acts as a tetradentate ligand, which incorporates a piperazine-fused ring. The structural parameters illustrate well the reinforcing effect exerted by the double “straps” of the piperazine molecule.

Über das Oxomolybdat AgKCu3Mo4O16 mit Silber in siebenfacher Koordination / About the Oxomolybdate AgKCu3Mo4O16 with Silver in Seven-Fold Coordination

1995 ◽  
Vol 50 (2) ◽  
pp. 252-256 ◽  
Author(s):  
H. Szillat ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Monoclinic Symmetry ◽  
Space Group ◽  
X Ray ◽  
Silver Copper ◽  
Symmetry Space ◽  
Symmetry Space Group

Single crystals of AgKCu3Mo4O16 have been prepared by crystallization from melts and investigated by X-ray diffractometer techniques. This compound crystallizes with monoclinic symmetry, space group C2h5 - P21/c, a = 5.056(1), b = 14.546(4), c = 19.858(9) Å, β = 86.64(5)°, Z = 4. The crystal structure of AgKCu3Mo4O16 is closely related to K2Cu3Mo4O16 showing ribbons of edge-sharing CuO6 and AgO7 polyhedra. The ribbons are linked by tetrahedrally coordinated molybdenum and K2O10 groups. Another kind of MoO4 tetrahedra occupies the cavities inside the ribbons. The crystal structure and the coordination of silver, copper, potassium and molybdenum by oxygen are discussed with respect to K2Cu3Mo4O16.

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