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論文

Magnetoferroelectric phase transition induced by latent spin-lattice coupling in the geometrically frustrated magnet $$mathrm{CuFe_{0.95}Al_{0.05}O_{2}}$$

玉造 博夢; 内原 猛*; 満田 節生*; 石井 祐太*; 中尾 裕則*; 竹端 寛治*; 今中 康貴*

Physical Review B, 111(13), p.134403_1 - 134403_9, 2025/04

https://doi.org/10.1103/PhysRevB.111.134403

In multiferroic CuFe$$_{0.95}$$Al$$_{0.05}$$O$$_{2}$$, applying uniaxial pressure $$p$$ generates a magnetoferroelectric phase distinct from the well-studied spin-driven ferroelectric phase associated with helical magnetic ordering in this system. Using a four-circle neutron diffractometer, the magnetic structure of the $$p$$-induced magnetoferroelectric phase is determined as the collinear sinusoidal type, which itself does not break the inversion symmetry in this system. Additionally, synchrotron radiation X-ray diffraction experiments are conducted to investigate how the triangular lattice in CuFe$$_{0.95}$$Al$$_{0.05}$$O$$_{2}$$ is distorted by applied $$p$$. Although lattice distortion during the magnetic phase transition in CuFe$$_{0.95}$$Al$$_{0.05}$$O$$_{2}$$ is mitigated by the substitution of nonmagnetic Al$$^{3+}$$, the application of $$p$$ along the conjugate direction revives the "latent" spin-lattice coupling, causing the triangular lattice to distort during magnetic phase transition. The application of a magnetic filed considerably reduces $$p$$-induced ferroelectric polarization, but does not affect lattice distortion. These results indicate that $$p$$-induced ferroelectric polarization is not a consequence of the piezoelectric effect. Instead, the sinusoidal magnetic structure would contribute to the emergence of $$p$$-induced ferroelectric polarization through spin-lattice coupling.

論文

Crystal structures of ReO$$_3$$ under hydrostatic pressure; A Combined neutron, X-ray, Raman, and first-principles calculation study

Efthimiopoulos, I.*; Klotz, S.*; Kunc, K.*; Baptiste, B.*; Chauvigne, P.*; 服部 高典

Physical Review B, 111(13), p.134103_1 - 134103_13, 2025/04

https://doi.org/10.1103/PhysRevB.111.134103

X線回折、中性子回折、ラマン散乱、第一原理計算を用いて、ReO$$_3$$の高圧力下での挙動を15GPaまで包括的に調べた。常圧$$Pm$$=3$$m$$構造は0.7GPaで空間群$$Im$$=3の立方晶相に連続的に相転移し、その後少なくとも15GPaまで安定であることがわかった。過去この圧力領域で報告されていた単斜晶$$C2/c$$構造や菱面体晶$$R$$=3$$c$$構造への転移は、試料に高輝度放射光X線を照射したことによる試料の劣化によるものであり、人工的なものであることが分かった。また今回、$$Im$$=3相の構造の圧力依存性と正確な状態方程式および天然試料と同位体濃縮$$^{18}$$O試料のラマン散乱データを示した。このデータから、リジッドなReO$$_6$$八面体が圧力とともに回転することによって、相転移および高密度化が起こることが分かった。

論文

Intrinsic low-temperature magnetic properties on ultraclean UTe$$_2$$ with $$T_c$$ = 2.1 K revealed by $$^{125}$$Te NMR

松村 拓輝*; 徳永 陽; 酒井 宏典; 神戸 振作; 他13名*

Physical Review B, 111(9), p.094507_1 - 094507_9, 2025/03

https://doi.org/10.1103/PhysRevB.111.094507

To investigate the intrinsic magnetic properties of UTe$$_2$$, we performed $$^{125}$$Te-NMR measurements on the ultra-clean single-crystalline UTe$$_2$$ with superconducting transition temperature $$T_c$$ = 2.1 K and compared the results with those of the $$T_c$$ = 1.6 K sample. The broadening of the linewidth of the NMR spectrum in the a-axis magnetic field and the low-temperature magnetic fluctuations observed in the 1.6 K sample are suppressed in the ultra-clean sample, indicating that such magnetic properties originate from a tiny amount of U deficiency. The present results suggest that the magnetic properties in UTe$$_2$$ are sensitive to the U deficiency. We also observed a peculiar angular dependence of the NMR quantities due to large magnetic anisotropy with the a-axis as the magnetic easy axis.

論文

Spin-singlet ground state with spin gap in $$S_{rm eff}$$ = $$frac{1}{2}$$ antiferromagnetic tetramer compound Yb$$_2$$SiO$$_5$$

長谷 正司*; 金子 耕士; 田端 千紘; 山内 宏樹; 辻井 直人*; D$"o$nni, A.*

Physical Review B, 111(9), p.094403_1 - 094403_9, 2025/03

https://doi.org/10.1103/PhysRevB.111.094403

We studied magnetic properties of Yb$$_2$$SiO$$_5$$ having pseudospins of $$S_{rm eff}$$ = $$frac{1}{2}$$ using magnetization, specific heat, and inelastic neutron scattering (INS) measurements. We observed cluster-like excitations in the INS measurements. We determined that the spin system in Yb$$_2$$SiO$$_5$$ is the $$S_{rm eff}$$ = $$frac{1}{2}$$ AFM tetramer with two exchange interactions of $$J_1 = 0.74$$ and $$J_2 = 0.95$$~meV. The spin tetramer can explain the excitation energies, $$chi (T)$$, magnetic specific heat at $$T < 15$$~K, and the magnitude of the scattering vector ($$Q$$) dependence of the intensity [$$I(Q)$$] at 0.7 and 1.2 meV. The spin tetramer, however, cannot explain well $$I(Q)$$ at 1.9 meV and $$I(T)$$ of the three excitations probably due to effects of weak inter-tetramer interactions.

論文

Magnetic and quadrupole coupling emerging in NdB$$_4$$ with geometrically frustrated orthogonal antiferromagnetic dimer

目時 直人; 山内 宏樹; 萩原 雅人; 綿貫 竜太*; 河村 聖子; 古府 麻衣子*; 中島 健次; 松田 雅昌*

Physical Review B, 111(10), p.104424_1 - 104424_9, 2025/03

https://doi.org/10.1103/PhysRevB.111.104424

フラストレートしたシャストリ・サザランド格子を有するNdB$$_4$$の磁気転移を理解する目的で中性子非弾性散乱実験を行った。$$|pm frac{5}{2}rangle$$と$$|pm frac{7}{2}rangle$$による準四重項状態が磁気秩序相で4つに分裂する。スペクトルは磁気相互作用$$langle J_x rangle J_x$$、磁気$$J_x$$と四極子$$O_{zx}$$の結合、そして一軸的な結晶場により説明される。この$$f$$電子状態により、主たる秩序変数である面内磁気モーメント$$m_perp=langle J_x rangle$$と結く誘起された2次的な秩序変数$$m_c=langle J_z rangle$$を説明することができた。幾何学的フラストレーションによってハイゼンベルグ相互作用が打ち消し合う状況で、磁気と四極子の結合が本質的な役割をすることが明らかになった。

論文

Nonreciprocal resonant surface acoustic wave absorption in Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$

Ba, Y.*; 山本 慧; 他6名*

Physical Review B, 111(10), p.104401_1 - 104401_15, 2025/03

https://doi.org/10.1103/PhysRevB.111.104401

Ferrimagnet insulator yttrium iron garnet (Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$, YIG) attracts much interest in magnonics and microwave applications due to its relatively low magnetic damping and long magnon relaxation time. The magnetoelastic interaction between YIG magnetization and surface acoustic waves (SAWs) has been the basis in the development of acoustic-surface-wave isolators. However, the investigation of SAW-driven magnetic resonance in YIG is limited by the low compatibility of YIG and SAW devices. In this work, we demonstrate nonreciprocal resonant SAW absorption in an on-chip YIG-SAW device integrated by the focused ion beam technique. We observed two distinct SAW absorption signals attributed to the perpendicular standing spin waves (PSSW). Furthermore, the large observed nonreciprocity is compared to theoretical predictions incorporating the influence of asymmetric surface conditions on PSSW mode profiles and nonreciprocal magnon-SAW coupling. The strongly nonreciprocal SAW attenuation in YIG offers a promising opportunity for highly efficient rf signal processing technologies.

論文

Theory of the spin Seebeck effect influenced by crystal-field excitations in Tb$$_3$$Fe$$_5$$O$$_{12}$$

森 道康; Tomasello, B.*; Ziman, T.*

Physical Review B, 111(1), p.014407_1 - 014407_12, 2025/01

https://doi.org/10.1103/PhysRevB.111.014407
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

The spin Seebeck effect (SSE) is a phenomenon of thermoelectric generation that occurs within a device consisting of a bilayer of a metal and a ferromagnet. When Tb$$_3$$Fe$$_5$$O$$_{12}$$ (TbIG) is substituted for the ferromagnet, the effect goes to zero at low temperatures, yet it increases to positive values with the application of a magnetic field. This is opposite to the expectation that the SSE should be suppressed by a magnetic field due to the increase in ${the}$ magnon gap. In this paper, the crystal-field excitations (CFE) in TbIG are calculated within a mean field theory exploiting the parameters of Terbium Gallium Garnet Tb$$_3$$Fe$$_5$$O$$_{12}$$ (TGG) from the neutron-scattering experimental literature. Like TGG, the primitive cell of TbIG hosts twelve Tb sites with six inequivalent magnetic sublattices, but due to the net $$[111]$$-molecular field from the tetrahedral and octahedral Fe ions, these can be classified into two distinct groups, the $$mathbf{C}$$ and the $$mathbf{C'}$$ sites, which account for the "double umbrella" magnetic structure. We show that when an external magnetic field is applied along the [111] direction of the crystal, the lowest CFE of the $$mathbf{C}$$ sublattices decreases. As a consequence of the magnetic field dependence of the lowest CFE, we find that at low temperatures the SSE in TbIG can result enhanced by an applied magnetic field.

論文

Multiple metamagnetic transitions in the helical antiferromagnet CeVGe$$_{3}$$

Jin, H.*; Choi, E. S.*; Wu, H.-C.*; Curro, N. J.*; 那波 和宏*; 佐藤 卓*; 鬼柳 亮嗣; 大原 高志; Klavins, P.*; Taufour, V.*

Physical Review B, 111(3), p.035103_1 - 035103_7, 2025/01

https://doi.org/10.1103/PhysRevB.111.035103
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

We report on neutron diffraction, magnetoresistance, magnetization and magnetic torque measurements under high magnetic field in the helical antiferromagnet CeVGe$$_{3}$$. This compound exhibits Kondo lattice coherence and helical antiferromagnetic (AFM) ordering at ambient pressure, similar to the well-studied CeRhIn$$_{5}$$. Our measurements reveal that CeVGe$$_{3}$$ undergoes a magnetic transition from an incommensurate (ICM) AFM state to an up-up-down-down commensurate (CM) AFM structure, followed by a transition to a novel phase at higher fields. A quantum phase transition occurs around 21.3 T. This rich magnetic field phase diagram closely resembles that of CeRhIn$$_{5}$$. Furthermore, angle-dependent magnetoresistance measurements reveal that all transitions in CeVGe$$_{3}$$ occur from the field component along the ab plane. These findings highlight the intricate interplay among exchange interactions, crystal field effects, ground state properties, and crystalline symmetries.

論文

Interfacial Dzyaloshinskii-Moriya interaction in nonmagnetic/noncollinear-antiferromagnetic bilayers

山根 結太*; 荒木 康史; 深見 俊輔*

Physical Review B, 111(14), p.144412_1 - 144412_9, 2025/00

https://doi.org/10.1103/PhysRevB.111.144412

We study the Dzyaloshinskii-Moriya interaction (DMI) appearing at the interface of a nonmagnetic/noncollinear-antiferromagnetic bilayer. The DMI is an antisymmetric exchange interaction between neighboring magnetic spins, arising in the absence of an inversion center between the spins, the explicit expression of which is dictated by system symmetry. We formulate the interfacial DMI for different crystalline orientations of the noncollinear antiferromagnet with a stacked-kagome lattice structure. From this formulation, we show that, when the kagome planes are perpendicular to the sample film plane, the DMI serves as a uniaxial magnetic anisotropy for the antiferromagnetic order parameter. Our findings reveal an important physical manifestation of a DMI, shedding light on microscopic mechanisms of the magnetic anisotropy in noncollinear antiferromagnets.

論文

Large spontaneous Hall effect with flexible domain control in the antiferromagnetic material TaMnP

小手川 恒*; 中村 彰良*; Huyen, V. T. N.*; 新井 祐樹*; 藤 秀樹*; 菅原 仁*; 林 純一*; 武田 圭生*; 田端 千紘; 金子 耕士; et al.

Physical Review B, 110(21), p.214417_1 - 214417_8, 2024/12

https://doi.org/10.1103/PhysRevB.110.214417
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

In this study, we show that the orthorhombic system TaMnP exhibits a large anomalous Hall conductivity (AHC) in spite of the small net magnetization. Neutron scattering experiment and the observation of the AH effect comprehensively suggest a dominant AF structure in TaMnP is represented by $$B_{3g}$$. The AHC is one of the largest among those observed in AF materials at zero fields. First-principles calculations suggest that the spin-orbit interaction originating in nonmagnetic Ta-5$$d$$ electrons significantly contributes to the enhancement of Berry curvatures in the momentum space. We found that the AF domain switching is triggered by the magnetic fields along all the crystal axes. This indicates that the AF domain determining the sign of the Hall response can be controlled even through the small net magnetization symmetrically different.

論文

Imaging Josephson vortices on curved junctions

藤澤 唯太*; Krishnadas, A*; Nakamura, Tomonori*; Hsu, C.-H.*; Smith, B. R. M.*; Pardo-Almanza, M*; Hiyane, Hoshu*; 永井 佑紀; 町田 理*; 岡田 佳憲*

Physical Review B, 110(22), p.224511_1 - 224511_5, 2024/12

https://doi.org/10.1103/PhysRevB.110.224511
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

エキゾチックな超伝導体の超伝導磁束の振る舞いを明らかにすることは、今後のデバイス開発にとって重要である。超伝導体LiTi$$_{2}$$O$$_{4}$$(111)の薄膜を作製し、磁場中での電子状態を走査型トンネル顕微鏡によって観測した。その際、接合部分の曲率に応じて超伝導磁束の状態が大きく変化することがわかった。そして、その変化は理論計算によっても確かめられた。この結果は、Josephson磁束を実験的な構造変化によってコントロールできる可能性を示唆しており、今後の新たなデバイス開発において重要な結果となるだろう。

論文

Relationship between orbital moment anisotropy, magnetocrystalline anisotropy, and Dzyaloshinskii-Moriya interaction in W/Co/Pt trilayers

Chi, Z.*; 芝田 悟朗; 藤森 淳; 他15名*

Physical Review B, 110, p.184401_1 - 184401_8, 2024/11

https://doi.org/10.1103/PhysRevB.110.184401
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

We have studied the Co layer thickness dependences of magnetocrystalline anisotropy (MCA), Dzyaloshinskii-Moriya interaction (DMI), and orbital moment anisotropy (OMA) in W/Co/Pt trilayers, in order to clarify their correlations with each other. We find that the MCA favors magnetization along the film normal and monotonically increases with decreasing effective magnetic layer thickness ($$t_{rm eff}$$). The magnitude of the Dzyaloshinskii-Moriya exchange constant ($$|D|$$) increases with decreasing $$t_{rm eff}$$ until $$T_{rm eff}$$ $$sim$$ 1 nm, below which $$|D|$$ decreases. The MCA and $$|D|$$ scale with 1/$$T_{rm eff}$$ for $$t_{rm eff}$$ larger than $$sim 1$$ nm, indicating an interfacial origin. Using X-ray magnetic circular dichroism (XMCD), we find non-zero OMA when $$t_{rm eff}$$ is smaller than $$sim 0.8$$ nm. The OMA increases with decreasing $$t_{rm eff}$$ more rapidly than what is expected from the MCA, indicating that factors other than OMA contribute to the MCA at small $$t_{rm eff}$$.

論文

Nonferroelectric phase with loss of cycloidal magnetic structure in Tb$$_{0.515}$$Gd$$_{0.485}$$Mn$$_{2}$$O$$_{5}$$

石井 裕太*; 坂倉 輝俊*; 石川 喜久*; 鬼柳 亮嗣; Lustikova, J.*; 青山 拓也*; 大串 研也*; 若林 裕助*; 木村 宏之*; 野田 幸男*

Physical Review B, 110(18), p.184404_1 - 184404_7, 2024/11

https://doi.org/10.1103/PhysRevB.110.184404
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Neutron-scattering measurements were employed to investigate the magnetic ordering in Tb$$_{1-x}$$Gd$$_{x}$$Mn$$_{2}$$O$$_{5}$$ (x = 0.485) enriched with the $$^{160}$$Gd isotope, a member of multiferroic RMn$$_{2}$$O$$_{5}$$ (R = rare-earth element) compounds. This material, at low temperatures, exhibits commensurate magnetic (CM) ordering, which drives electric polarization. Notably, electric polarization diminishes as the temperature decreases further, while the CM ordering persists. Magnetic structure analyses revealed that a cycloidal magnetic structure along the c axis transforms into a sinusoidal-like structure, resulting in the nonferroelectric phase, whereas a collinear magnetic structure in the ab plane exhibits no significant change. The findings suggest that the cycloidal magnetic structure plays a key role in inducing electric polarization in the CM ordering of the present material.

論文

Spin pumping into quantum spin chains

古谷 峻介*; 松尾 衛; 加藤 岳生*

Physical Review B, 110(16), p.165129_1 - 165129_13, 2024/10

https://doi.org/10.1103/PhysRevB.110.165129
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

We theoretically investigate spin pumping into a quantum easy-plane ferromagnetic spin chain system. This quantum spin chain is effectively described by the Tomonaga-Luttinger (TL) liquid despite the ferromagnetic exchange interaction because of the easy-plane magnetic anisotropy. This TL liquid state has an extremely strong interaction that is hardly realized in other quantum antiferromagnetic chain systems or weakly interacting electron systems. We show how the strongly interacting TL liquid affects the ferromagnetic resonance that occurs in the ferromagnetic insulator. In particular, we discuss the dependence of the Gilbert damping on the temperature and the junction length. The Gilbert damping allows us to extract information about the above-mentioned strong interaction within the quantum ferromagnetic spin chain. We also point out that a well-known compound CsCuCl$$_{3}$$ will be suitable for the realization of our setup.

論文

Ca-induced phonon softening in BaTiO$$_{3}$$ revealed by inelastic X-ray and neutron scattering

木村 耕治*; 筒井 智嗣*; 山本 裕太*; 中埜 彰俊*; 川村 啓介*; 梶本 亮一; 蒲沢 和也*; Martin, A.*; Webber, K. G.*; 柿本 健一*; et al.

Physical Review B, 110(13), p.134314_1 - 134314_10, 2024/10

https://doi.org/10.1103/PhysRevB.110.134314
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

We performed inelastic X-ray and neutron scattering (IXS and INS) experiments for (Ba,Ca)TiO$$_{3}$$ single crystals to elucidate the effect of Ca doing on the atomic dynamics. Dispersion relations of transverse phonons in BaTiO$$_{3}$$, (Ba$$_{0.9}$$Ca$$_{0.1}$$)TiO$$_{3}$$, and (Ba$$_{0.8}$$Ca$$_{0.2}$$)TiO$$_{3}$$ were determined. The $textit{A}$-site-O vibrational mode as well as the acoustic mode were observed both by IXS and INS, whereas the Ti-O soft mode was detected only by INS. It was found that the $textit{A}$-site-O vibration exhibits significant softening with increasing Ca concentration, while the Ti-O soft mode is almost unaffected by the Ca doping. This finding is discussed in comparison with the polarization hysteresis loops and piezoelectric coefficients of (Ba,Ca)TiO$$_{3}$$. It is indicated that the softening of the $textit{A}$-site-O vibration contributes to the enhancement of the piezoelectricity of Ca-doped BaTiO$$_{3}$$-based materials.

論文

Ferrimagnetic structure in the high-pressure phase of $$alpha$$-Mn

荒木 新吾*; 岩本 凱成*; 秋葉 和人*; 小林 達生*; 宗像 孝司*; 金子 耕士; 長壁 豊隆

Physical Review B, 110(9), p.094420_1 - 094420_7, 2024/09

https://doi.org/10.1103/PhysRevB.110.094420
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

$$alpha$$-Mn相は、自発磁化が0.02$${mu}_{rm B}$$/Mnと比較的小さいにもかかわらず、圧力誘起弱強磁性(WFM)状態で大きな異常ホール効果(AHE)を示す。このAHEの背後にある根本的な機構を理解するために、2.0GPaの圧力下で単結晶中性子回折測定を行い、WFM相の磁気構造を決定した。I、II、III-1、IV-1位置のMnは、ほぼコリニアーな磁気モーメントが[001]方向に揃ったフェリ磁性構造を持つことを見出した。一方で、III-2とIV-2位置のMnの微小な磁気モーメントは(001)面内を向いている。この磁気構造で計算したネットの磁気モーメントの大きさ(-0.020$${pm}$$0.005)$${mu}_{rm B}$$/Mn原子)は、実験で決定された自発磁化と非常によく一致する。$$q$$ = (0, 0, 0)での磁気反射の観測は、AHEの出現の重要な条件を満たしている。

論文

Octupolar edge state in an $$e_g$$ orbital system on a square lattice

久保 勝規

Physical Review B, 110(7), p.075110_1 - 075110_7, 2024/08

https://doi.org/10.1103/PhysRevB.110.075110
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

A tight-binding model for $$e_g$$ orbitals on a square lattice is investigated. We consider only the nearest-neighbor hopping and the model is characterized by two hopping parameters, $$t_1$$ and $$t_2$$. There are Dirac points in the electronic band structure and the type of the Dirac points (type-I or type-II) depends on the ratio $$t_2/t_1$$. For the case of the type-I Dirac points, edge states appear for a lattice with edges perpendicular to the $$[11]$$ direction. The edge states at a certain momentum along the edges have octupole moments with opposite signs between the right and left edges. Thus, these edge states can be called helical octupolar edge states. This study bridges the research fields of topological phenomena and multipole physics.

論文

Theory of the inverse Rashba-Edelstein effect induced by thermal spin injection

細川 海慈*; 山 正樹*; 松尾 衛; 加藤 岳生*

Physical Review B, 110(3), p.035309_1 - 035309_12, 2024/07

https://doi.org/10.1103/PhysRevB.110.035309
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Our result provides an important foundation for an accurate analysis of the inverse Rashba-Edelstein effect induced by thermal spin injection.

論文

Lattice dynamics of CH(NH$$_{2}$$)$$_{2}$$PbI$$_{3}$$ and CH(NH$$_{2}$$)$$_{2}$$SnI$$_{3}$$ investigated by inelastic X-ray scattering and comparison of their elastic properties

玉造 博夢; 村上 洋一*; 齋藤 紀子*; 大橋 直樹*; 筒井 智嗣*

Physical Review B, 110(2), p.024301_1 - 024301_8, 2024/07

https://doi.org/10.1103/PhysRevB.110.024301
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Using the inelastic X-ray scattering (IXS) technique, we investigate the lattice dynamics of inorganic-organic hybrid iodide perovskites FAPbI$$_{3}$$ and FASnI$$_{3}$$ (FA $$equiv$$ CH(NH$$_{2}$$)$$_{2}$$, formamidinium) in their cubic $$alpha$$ phase and tetragonal $$beta$$ phase. We find that the IXS spectra of FASnI$$_{3}$$ are highly broad at all momentum points, as has been widely observed in the Pb-based halide perovskites. The speeds of sound (phonon group velocities) and absolute values of elastic constants of FASnI$$_{3}$$ are smaller than those of FAPbI$$_{3}$$ in both phases. In addition, no significant difference in the phonon lifetimes of FAPbI$$_{3}$$ and FASnI$$_{3}$$ is observed. These results correlate better with the reported tendency that the lattice thermal conductivity of ASnX$$_{3}$$ is lower than that of APbX$$_{3}$$. We discuss that our results also favor the up-conversion mechanism by acoustic phonons in the phonon bottleneck effect for the long lifetime of hot carriers.

論文

Elastic and inelastic neutron scattering experiments under high pressure in the frustrated antiferromagnet CuFeO$$_{2}$$

寺田 典樹*; Khalyavin, D. D.*; Manuel, P.*; 浅井 晋一郎*; 益田 隆嗣*; 齋藤 開*; 中島 多朗*; 長壁 豊隆

Physical Review B, 110(2), p.024406_1 - 024406_9, 2024/07

https://doi.org/10.1103/PhysRevB.110.024406
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

フラストレート反強磁性体CuFeO$$_{2}$$は、圧力により、コメンシュレートなコリニアー相(CM1)からいくつかのインコメンシュレートでノンコリニアーな相への複雑な磁気相転移を示す。圧力が磁気相互作用に及ぼす影響を調べるために、高圧下で中性子回折および非弾性中性子散乱実験を行った。圧力が増すと、CM1基底状態は臨界圧力($${P}$$ $$leqq$$ 3GPa)以下でも磁場の印加に対して不安定になる。これは、2.1GPaで臨界磁場$${H_{c1}}$$が7.5Tから4.5Tに大幅に減少したことで確かめられた。さらに、スピン波分散関係のエネルギーギャップは、$$P$$=2.1GPaの圧力印加によって1.0meVから0.88meVに減少する。実験結果をスピン波計算と比較すると、スピン波励起の変化は、一軸異方性項または最近接交換相互作用の分離度のいずれかの減少によって説明できることがわかった。

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