707 research outputs found
Magnetic ground state and multiferroicity in BiMnO
We argue that the centrosymmetric symmetry in BiMnO is
spontaneously broken by antiferromagnetic (AFM) interactions existing in the
system. The true symmetry is expected to be , which is compatible with the
noncollinear magnetic ground state, where the ferromagnetic order along one
crystallographic axis coexists with the the hidden AFM order and related to it
ferroelectric polarization along two other axes. The symmetry can be
restored by the magnetic field Tesla, which switches off the
ferroelectric polarization. Our analysis is based on the solution of the
low-energy model constructed for the 3d-bands of BiMnO, where all the
parameters have been derived from the first-principles calculations. Test
calculations for isostructural BiCrO reveal an excellent agreement with
experimental data.Comment: 5 pages, 5 figure
Π‘ΠΈΠ½ΡΠ΅Π· ΠΈ ΡΠ²ΠΎΠΉΡΡΠ²Π° ΡΠΈΠ»ΠΈΠΊΠ°ΡΠΎΠ² Π²ΠΈΡΠΌΡΡΠ°, ΠΏΡΠΈΠ³ΠΎΡΠΎΠ²Π»Π΅Π½Π½ΡΡ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ ΠΌΠ΅Ρ Π°Π½ΠΈΡΠ΅ΡΠΊΠΎΠΉ Π°ΠΊΡΠΈΠ²Π°ΡΠΈΠΈ
Π Π½Π°ΡΡΠΎΡΡΠ΅ΠΉ ΡΠ°Π±ΠΎΡΠ΅ Π±ΡΠ»ΠΈ ΡΠΈΠ½ΡΠ΅Π·ΠΈΡΠΎΠ²Π°Π½Ρ ΡΠ΅ΡΠΈΠΈ ΡΠΈΠ»ΠΈΠΊΠ°ΡΠΎΠ² Π²ΠΈΡΠΌΡΡΠ° ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΎΠΉ Π°ΠΊΡΠΈΠ²Π°ΡΠΈΠΈ, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½Ρ ΠΈΡ
ΡΠ²ΠΎΠΉΡΡΠ²Π° ΡΠ°ΠΊΠΈΠΌΠΈ ΠΌΠ΅ΡΠΎΠ΄Π°ΠΌΠΈ, ΠΊΠ°ΠΊ Π’Π-ΠΠ‘Π Π°Π½Π°Π»ΠΈΠ· ΠΈ Π Π€Π-ΡΠΏΠ΅ΠΊΡΡΠΎΡΠΊΠΎΠΏΠΈΡ. Π£ΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΎ, ΡΡΠΎ Π΄Π»Ρ ΡΠ΅ΡΠΈΠΈ, ΠΏΡΠΈΠ³ΠΎΡΠΎΠ²Π»Π΅Π½Π½ΠΎΠΉ Ρ ΡΠΎΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠ΅ΠΌ ΡΠ΅Π°Π³Π΅Π½ΡΠΎΠ² Bi:Si = 2:1 ΠΏΠΎΡΠ»Π΅ 800 Β°Π‘ Π½Π°ΡΡΡΠΏΠ°Π΅Ρ ΠΏΠ»Π°Π²Π»Π΅Π½ΠΈΠ΅, ΡΠΎΠ³Π΄Π° ΠΊΠ°ΠΊ Π΄Π»Ρ ΡΠ΅ΡΠΈΠΈ Ρ ΡΠΊΠ²ΠΈΠ°ΡΠΎΠΌΠ½ΡΠΌ ΡΠΎΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠ΅ΠΌ Bi ΠΈ Si Π² ΠΈΡΡ
ΠΎΠ΄Π½ΡΡ
ΡΠ΅Π°Π³Π΅Π½ΡΠ°Ρ
ΠΏΠ»Π°Π²Π»Π΅Π½ΠΈΡ Π² ΡΡΠΎΠΌ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΠΎΠΌ ΠΈΠ½ΡΠ΅ΡΠ²Π°Π»Π΅ Π½Π΅ Π½Π°Π±Π»ΡΠ΄Π°Π΅ΡΡΡ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΠΏΡΠΈ ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠΈ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΡ ΠΏΡΠΎΠΊΠ°Π»ΠΈΠ²Π°Π½ΠΈΡ Ρ 500ΛΠ‘ Π΄ΠΎ 700 Β°Π‘ ΡΠ°Π·Π° ΠΌΠ΅ΡΠ°ΡΠΈΠ»ΠΈΠΊΠ°ΡΠ° Π²ΠΈΡΠΌΡΡΠ° (Bi2SiO5) ΠΏΠΎΠ»Π½ΠΎΡΡΡΡ ΠΏΠ΅ΡΠ΅Ρ
ΠΎΠ΄ΠΈΡ Π² ΠΎΡΡΠΎΡΠΈΠ»ΠΈΠΊΠ°Ρ Π²ΠΈΡΠΌΡΡΠ° (Bi4Si3O12), Π° Π΄ΠΎΠ»Ρ ΡΠ°Π·Ρ ΡΠΈΠ»Π»Π΅Π½ΠΈΡΠ° (Bi12SiO20) ΡΠ²Π΅Π»ΠΈΡΠΈΠ²Π°Π΅ΡΡΡ ΠΏΡΠΈ ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠΈ ΡΠΎΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΡ Bi:Si
Universal magneto-orbital ordering in the divalent -site quadruple perovskite manganites MnO ( = Ca, Sr, Cd, and Pb)
Through analysis of variable temperature neutron powder diffraction data, we
present solutions for the magnetic structures of SrMnO,
CdMnO, and PbMnO in all long-range ordered phases. The
three compounds were found to have magnetic structures analogous to that
reported for CaMnO. They all feature a higher temperature lock-in
phase with \emph{commensurate} magneto-orbital coupling, and a delocked,
multi-\textbf{k} magnetic ground state where \emph{incommensurate}
magneto-orbital coupling gives rise to a constant-moment magnetic helix with
modulated spin helicity. CdMnO represents a special case in which
the orbital modulation is commensurate with the crystal lattice and involves
stacking of fully and partially polarized orbital states. Our results provide a
robust confirmation of the phenomenological model for magneto-orbital coupling
previously presented for CaMnO. Furthermore, we show that the model
is universal to the quadruple perovskite manganites synthesised to
date, and that it is tunable by selection of the -site ionic radius
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