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脇本 秀一; 木村 宏之*; 坂本 勇馬*; 福永 守*; 野田 幸男*; 武田 全康; 加倉井 和久
Physical Review B, 88(14), p.140403_1 - 140403_5, 2013/10
被引用回数:19 パーセンタイル:62.14(Materials Science, Multidisciplinary)We have performed simultaneous measurements of magnetic chirality by using polarized neutrons and electric polarization along the -axis of single crystals of YMn
(Mn
Ga
)
O
with
and
, in which nonmagnetic Ga-ions dilute Mn
spins. Measurements conducted under zero field heating after various field-cooling conditions evidence that the magnetic chirality of Mn
cycloidal spins plays a dominant role in the incommensurate magnetic (ICM) phase, whereas the magnetic exchange striction by the Mn
-Mn
chain plays a dominant role in the commensurate magnetic (CM) phase. The polarization of YMn
O
flips upon CM to ICM phase transition because the ferroelectricity driven by the magnetic chirality and the exchange striction provides opposite directions of polarization.
福永 守*; 坂本 勇馬*; 木村 宏之*; 野田 幸男*; 阿部 伸行*; 谷口 耕治*; 有馬 孝尚*; 脇本 秀一; 武田 全康; 加倉井 和久; et al.
Physical Review Letters, 103(7), p.077204_1 - 077204_4, 2009/08
被引用回数:50 パーセンタイル:86.29(Physics, Multidisciplinary)We discovered a reversible electric polarization flop from the axis (
) to the
axis (
) in multiferroic TmMn
O
below 5 K by applying a magnetic field of approximately 0.5 T along the
axis. This phenomenon is the first example of the rare-earth (
) compound
Mn
O
. This magnetic-field-induced polarization flop corresponds to a magnetic phase transition from one incommensurate magnetic (ICM)
phase to another ICM
phase, which is equivalent to an ICM
phase above 5 K under no magnetic field. The spin chirality in the
plane, which was observed in the
phase by polarized neutron diffraction, disappeared in the ICM
phase. This indicates that the polarization in the ICM phases of TmMn
O
was induced by an
type interaction.
脇本 秀一; 加倉井 和久; 坂本 勇馬*; 福永 守*; 木村 宏之*; 野田 幸男*
no journal, ,
マルチフェロイック物質RMnO
の電気磁気効果の起源として、Mn
スピンのサイクロイドスピン構造に起因するS
S機構と、Mn
鎖とMn
鎖間の磁気相関に由来するexchange striction (S
S)機構が指摘されている。本研究では、YMn
O
のMn
を非磁性Ga
イオンに置換することでS
Sの影響を希釈し、JRR-3のTAS-1の偏極中性子でS
Sを観測してその効果を検証した。その結果、強誘電相の格子整合磁気秩序相ではS
S機構が強く、強誘電相の弱まる格子不整合磁気秩序相ではS
S機構が強く寄与することを明らかにした。
脇本 秀一; 木村 宏之*; 福永 守*; 坂本 勇馬*; 野田 幸男*; 加倉井 和久
no journal, ,
There are two candidates of the origin of the magnetic-driven ferroelectricity in YMnO
, one is the
model and the other is the
model. We have measured spin chirality and polarization of YMn
(Mn
Ga
)
O
where non-magnetic Ga ions dilute the
contribution. We have succeeded to separate these two contributions, and found that the
mechanism is dominant in the low-temperature phase while the
mechanism is dominant in the intermediate temperature phase.
脇本 秀一; 木村 宏之*; 福永 守*; 坂本 勇馬*; 加倉井 和久; 野田 幸男*
no journal, ,
マルチフェロイック物質であるRMnO
は、Mn
スピンのサイクロイドスピン構造に起因するS
S機構と、Mn
鎖とMn
鎖間の磁気相関に由来するexchange striction (S・S)機構が指摘されている。本研究では、YMn
O
のMn
を非磁性Ga
イオンに置換することでS・Sの影響を希釈し、JRR-3のTAS1の偏極中性子でS
Sを観測してその効果を検証した。結果、低温の格子非整合磁気秩序相においてはS
S機構が強く、高温の格子整合磁気秩序相ではS・S機構が強いことが明らかとなった。
鬼柳 亮嗣; 山崎 但*; 坂元 勇馬*; 木村 宏之*; 野田 幸男*; 大山 研司*; 鳥居 周輝*; 米村 雅雄*; Zhang, J.*; 神山 崇
no journal, ,
BiFeO (BFO) is well known as a room-temperature multiferroic material. The solid solution of BFO with another perovskite type ferroelectric material, BaTiO
(BTO), has been reported to have improved multiferroicity. In this presentation, the structural study of (1-
)BFO-
BTO system in order to clarify the relationship between the structure and the physical properties will be reported. From the structural analyses using neutron and X-ray powder diffraction data, it was found that there exist multiple phases in the wide range of
. The coexistence of a hexagonal phase and a cubic one was confirmed suggesting the origin of the ferroelectricity of the solution to be the hexagonal phase. Structural deformation with the variation of
was observed, which results in the lowering of the phase transition temperatures. Combining all the information, the whole phase diagram of BFO-BTO system with respect to temperature and the composition was drawn.
脇本 秀一; 木村 宏之*; 福永 守*; 坂本 勇馬*; 野田 幸男*; 加倉井 和久
no journal, ,
Mn
O
is a multiferroic compound in which ferroelectricity is driven by magnetism. So far two models have been proposed to explain spin-driven ferroelectriciry in this compound,
and
models. By detailed investigation of magnetic chirality by polarized neutron diffraction, we have succeeded to distinguish these two contributions to the ferroelectric polarization. We conclude that the
mechanism is dominant in the commensurate phase and the
mechanism is dominant in the low temperature incommensurate phase.
脇本 秀一; 木村 宏之*; 福永 守*; 坂本 勇馬*; 武田 全康; 加倉井 和久; 野田 幸男*
no journal, ,
A multiferroic compound YMnO
shows characteristic dielectric polarization flip upon the magnetic phase transition from commensurate magnetic (CM) to low-temperature incommensurate magnetic (LTICM) phases. By utilizing simultaneous measurements of dielectric polarization and magnetic chirality by polarized neutron diffraction, we have studied the direct relation between them. We have identified that
and
, two major mechanisms of spin-driven ferroelectricity, are dominant in the CM and LTICM phases, respectively, and concluded that a conservation of magnetic chirality gives rise to the polarization flip upon the CN-LTICM transition.