Magnetic Structures of Some Multiferroics

We studied crystal and magnetic structures of some composite and single-phase multiferroics: (x)MFe2O4 + (1-x)BaTiO3, Ni3-yCoyV2O8, and Bi0.9Ba0.1Fe0.9Ti0.1O3. Composite multiferroics (x)MFe2O4 + (1-x)BaTiO3 with x = (0.2; 0.3; 0.4) and M = (Ni, Co) have ferrimagnetic structure, which is described by the propagation vector k = 0. Oxides Ni3-yCoyV2O8 with y = (0.1; 0.3; 0.5) possess a modulated magnetic structure, described by the vector k = (δ, 0, 0), where δ = 0.283 and 0.348 at 7.4 K for y = 0.1 and 0.5, respectively. In the Bi0.9Ba0.1Fe0.9Ti0.1O3 multiferroic a magnetic order is destroyed at 600 K and the Fe-ion magnetic moment decreases from µ = 3.46(5) μB at 300 K to zero at 600 K.

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Multi-k magnetic order in Ca3CuNi2(PO4)4: irrep approach and Shubnikov symmetry

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314085416 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1458-C1458

Author(s):

Vladimir Pomjakushin

Keyword(s):

Experimental Data ◽

Magnetic Structure ◽

Magnetic Order ◽

Quantum Spin ◽

Expectation Values ◽

Space Group ◽

Magnetic Structures ◽

Propagation Vector ◽

Antiferromagnetic Structure ◽

Low Dimensional

The multi-k magnetic structures with propagation vectors k being the arms of the propagation vector star rarely can be justified experimentally. We show that the antiferromagnetic structure in the low dimensional quantum spin trimer system Ca3CuNi2(PO4)4 is based on the full star of propagation vector k=[1/2,1/2,0] of the paramagnetic space group C2/c. The relation between representation analysis in the propagation vector formalism and Shubnikov magnetic space group (MSG) symmetry is examined in details. A symmetry restrictive MSG that excellently fits the experimental data can be constructed only with the use of the full star. The magnetic structure is further supported by the calculations of the spin expectation values of the isolated Ni-Cu-Ni trimer with realistic Hamiltonian.

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Crystal and magnetic structures of R 2Ni1.78In compounds (R = Tb, Ho, Er and Tm)

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520621008179 ◽

2021 ◽

Vol 77 (5) ◽

pp. 824-832

Author(s):

Stanisław Baran ◽

Aleksandra Deptuch ◽

Andreas Hoser ◽

Bogusław Penc ◽

Yuriy Tyvanchuk ◽

...

Keyword(s):

Rare Earth ◽

Neutron Diffraction ◽

Magnetic Structure ◽

Magnetic Moments ◽

Symmetry Analysis ◽

Crystalline Electric Field ◽

Magnetic Structures ◽

Antiferromagnetic Ordering ◽

Crystal And Magnetic Structures ◽

The Rare Earth

The crystal and magnetic structures in R 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx , kx , ½], with kx equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.

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Magnetic Order in Quaternary NiMnGe:T (T = Cr, Ti) Compounds

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.289.156 ◽

2019 ◽

Vol 289 ◽

pp. 156-163

Author(s):

Andrzej Szytuła ◽

Stanislav Baran ◽

Bogusław Penc ◽

Andreas Hoser ◽

Vladimir Dyakonov

Keyword(s):

Simple Model ◽

Neutron Diffraction ◽

Magnetic Structure ◽

Magnetic Order ◽

Magnetic Interactions ◽

Néel Temperature ◽

Cr Content ◽

Propagation Vector ◽

Cr System ◽

Ti Content

The work reports the results of neutron diffraction measurements of NiMnGe:T systems where T is Cr or Ti. All investigated compounds have the helicoidal magnetic structure with the propagation vector k = (ka,0,0). The values of the ka component decrease with increasing Cr content and increase with increasing Ti content. For all compounds, except the sample with x = 0.18 in Cr-system, the helicoidal order is stable up to the Néel temperature. The obtained data are analysed based on simple model in which the magnetic interactions are described by two exchange integrals J1 > 0 for first and J2 < 0 for second neighbouring moments. This model clears up different dependence of ka component in different systems.

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Hydroflux Synthesis, Chemical and Thermal Instability, Crystal and Magnetic Structures of the Oxo-Hydroxoferrate K2–xFe4O7–x(OH)x

10.26434/chemrxiv.7346060 ◽

2018 ◽

Author(s):

Ralf Albrecht ◽

Jens Hunger ◽

Theresa Block ◽

Rainer Pöttgen ◽

Anatoliy Senyshyn ◽

...

Keyword(s):

Crystal Structure ◽

Magnetic Structure ◽

Powder Diffraction ◽

Thermal Instability ◽

Neutron Powder Diffraction ◽

Potassium Ions ◽

Ambient Conditions ◽

Magnetic Structures ◽

Vertex Sharing ◽

Crystal And Magnetic Structures

The reaction of Fe(NO3)3∙9 H2O with KOH under hydroflux conditions at about 200 °C produces red crystals of K2−xFe4O7–x(OH)x in a quantitative yield. In the crystal structure, edge-sharing [FeO6] octahedra form 2D-[Fe2O6] honeycomb nets. Pillars consisting of pairs of vertex-sharing [FeO4] tetrahedra link the honeycomb layers and form columnar halls in which the potassium ions are located. The trigonal (P3̅1m) and the hexagonal (P63/mcm) polytypes of K2−xFe4O7–x(OH)x show oriented intergrowth. The sub-stoichiometric potassium content (x = 0.3) is compensated by hydroxide ions. K2−xFe4O7–x(OH)x is an antiferromagnet above 2 K and its magnetic structure was determined by neutron powder diffraction. Under ambient conditions K2−xFe4O7–x(OH)x hydrolyzes and K2CO3·H2O forms gradually on the surface of the K2−xFe4O7–x(OH)x crystals. Upon annealing at air at about 500 °C, the potassium atoms in the columnar halls start to order into a superstructure.

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Crystal and Magnetic Structures of High Pressure Perovskite-Type Oxyfluorides,PbFeO2F and 0.5PbFeO2F-0.5PbTiO3 [Pb(Fe0.5Ti0.5)O2.5F0.5]

MRS Proceedings ◽

10.1557/proc-988-0988-qq06-03 ◽

2006 ◽

Vol 988 ◽

Cited By ~ 1

Author(s):

Tetsuhiro Katsumata ◽

Akihiro Takase ◽

Masashi Yoshida ◽

Yoshiyuki Inaguma ◽

John E. Greedan ◽

...

Keyword(s):

Magnetic Structure ◽

High Pressures ◽

Neel Temperature ◽

X Ray Diffraction ◽

Néel Temperature ◽

Magnetic Structures ◽

Ion Shifts ◽

A Site ◽

Perovskite Type ◽

Crystal And Magnetic Structures

AbstractThe perovskites PbFeO2F and 0.5PbFeO2F-0.5PbTiO3 were synthesized at high temperatures (1000°C) and high pressures (4 – 6 GPa). The crystal and magnetic structures were determined using powder neutron diffraction. Quenched PbFeO2F has the cubic perovskite-type, Pm3m, structure in which the Pb ion shifts from ideal A-site along the <110> directions, which is in good accordance with a previous report. The magnetic structure is antiferromagnetic G-type with propagation vector k = (1/2 1/2 1/2) and an Fe3+ ordered moment of 3.83 μB at 283K. The Néel temperature is 655(5) K. Annealed PbFeO2F has a tetragonal perovskite-type structure at room temperature and transforms reversibly from tetragonal to cubic at approximately 470 K. A superlattice with dimensions a × a × 5c is observed both in electron and x-ray diffraction. The solid solution 0.5PbFeO2F-0.5PbTiO3 belongs to the non-centrosymmetric space group P4mm. The magnetic structure is G-type antiferromagnetic and shows a weak ferromagnetic moment at 4 K. Consequently, 0.5PbFeO2F-0.5PbTiO3 is simultaneously ferroelectric and a weak ferromagnet at low temperature. The Néel temperature is 450 K but the temperature dependence of the ordered Fe moment is anomalous.

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