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Title: Crystalline and spin chiralities in multiferroics with langasite-type structure and Fe{sub 1–x}Co{sub x}Si crystals

It is shown that, when magnetic ordering occurs in layered iron-containing langasites (sp. gr. P321), one of the reasons for spin chiralities of different signs is the presence of structural chirality (the existence of inversion twins), which, in turn, is due to the nonsymmetricity of these crystals. Spin helicoids arise in these multiferroics at split sites of Fe{sup 3+} ions below the Néel point. The direction of electric polarization vectors coincides with the direction of the magnetic helicoid axes because of the piezoelectric properties of these materials. Due to the magnetostriction effects, structural chirality wave vector k{sub z} exceeds the magnetic helicoid wave vector by a factor of 2: k{sub z} = 2q{sub z}. The temperatures of transitions to the chiral structural and chiral magnetic states may differ. In particular, if the structural transition initial temperature exceeds the magnetic transition temperature (Τ{sub U}> Τ{sub M}), structural displacements may arise in the absence of magnetism at Τ{sub M} < Τ < Τ{sub U}. In noncentrosymmetric Fe{sub 1–x}Co{sub x}Si crystals (sp. gr. P2{sub 1}3), which are not multiferroics, magnetic chirality is due to the Dzyaloshinski–Moriya interaction. The dependence of the moduli of incommensurate wave number of the corresponding helicoid on the atomicmore » composition of the crystals under consideration is nonmonotonic.« less
Authors:
; ;  [1]
  1. Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)
Publication Date:
OSTI Identifier:
22472141
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 60; Journal Issue: 5; Other Information: Copyright (c) 2015 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHIRALITY; COBALT SILICIDES; CONCENTRATION RATIO; CRYSTALS; CUBIC LATTICES; IRON COMPOUNDS; IRON IONS; MAGNETISM; MAGNETIZATION; MAGNETOSTRICTION; NEEL TEMPERATURE; PHASE TRANSFORMATIONS; PIEZOELECTRICITY; POLARIZATION; SPIN; TRANSITION TEMPERATURE; TRIGONAL LATTICES