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山本 将隆*; 日高 宏之*; 柳澤 達也*; 田端 千紘; 中尾 裕則*; 下村 晋*; 小野寺 秀也*; 網塚 浩*
Journal of the Physical Society of Japan, 95(5), p.053703_1 - 053703_4, 2026/05
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)We report on the negative magnetization (NM) phenomenon characterized by a spontaneous magnetization antiparallel to an applied magnetic field in an antiferromagnetic (AFM) carbide TbNiC. The NM phenomenon in this compound is observed in the AFM state with a field cooling process at low magnetic fields below 500 Oe. The monotonic decrease in magnetization below the Neel temperature of 25 K observed in temperature dependence measurement of magnetization for TbNiC cannot be explained by Neel's classical theory of ferrimagnetism. We propose a novel ferrimagnetic model in which the NM originates from phase coupling between charge density wave and AFM orders.
清水 悠晴*; 橘高 俊一郎*; 河野 洋平*; 中村 翔太*; 芳賀 芳範; 山本 悦嗣; 町田 一成*; 網塚 浩*; 榊原 俊朗*
Physical Review B, 112(24), p.245157_1 - 245157_10, 2025/12
被引用回数：1 パーセンタイル：0.00(Materials Science, Multidisciplinary)We report the results of high-resolution dc magnetization and specific heat measurements on the unconventional superconductor UBe.Suppression of the non-Fermi-liquid behavior under field and a nontrivial fifth-order magnetic susceptibility were observed at low temperatures, suggesting the Fermi-surface reconstruction accompanying the crossover from non-Fermi-liquid to Fermi-liquid state in UBe.
B日高 宏之*; 柳澤 達也*; 田端 千紘; 今 布咲子*; 網塚 浩*; 清水 悠晴*; 青木 大*
Physical Review B, 112(14), p.144418_1 - 144418_6, 2025/10
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)A uranium-based metallic compound UNiB with orthorhombic structure exhibits an antiferromagnetic (AFM) ordering at 
= 20.4 K. Although an electric current-induced magnetization below has been observed in this compound [H. Saito et al., J. Phys. Soc. Jpn. 87, 033702 (2018)], its underlying mechanism remains controversial. In this study, we measured thermal expansion and magnetostriction along the a-axis under magnetic field 
up to 14 T applied within the 
-plane to investigate rotational symmetry of a magnetic field-temperature phase diagram in UNiB. From the phase diagrams constructed under various -angles between 
and 
, it is suggested that the -
phase diagram practically exhibits six-fold rotational symmetry in the plane despite the orthorhombic crystal structure, which would be attributed to 
quasi-hexagonal structure formed by U ions with small orthorhombic distortion.
田端 千紘; 今 布咲子*; 日比野 瑠央*; 清水 悠晴*; 網塚 浩*; 金子 耕士; 本間 佳哉*; 青木 大*; 中尾 裕則*
Journal of the Physical Society of Japan, 94(8), p.083701_1 - 083701_5, 2025/07
被引用回数：5 パーセンタイル：79.04(Physics, Multidisciplinary)Resonant X-ray scattering at the uranium M4 edge revealed successive phase transitions in URhSn. An antiferro-quadrupole (AFQ) order with propagation vector q = 0 emerges between 16 K and 54 K. Below 16 K, this AFQ order coexists with a canted magnetism, leading to a ground state that breaks mirror symmetry and exhibits chirality or polarity.
日高 宏之*; 柳谷 駿*; 小野寺 進太朗*; 柳澤 達也*; 網塚 浩*; 谷田 博司*; 石飛 尊之
Journal of the Physical Society of Japan, 94(3), p.034706_1 - 034706_9, 2025/03
被引用回数：4 パーセンタイル：79.04(Physics, Multidisciplinary)We investigated the magnetic-field direction anisotropy of the unknown ordered phase in the tetragonal compound CeCoSi through bulk physical property measurements. The anisotropy in the field direction, previously identified in X-ray diffraction experiments, where a field-induced phase appears along [100] but not along [110], was confirmed in the bulk properties. Combining these experimental results with Landau theory, we infer that the field-induced phase in the [100] direction emerges under an infinitesimally small magnetic field.
Si今 布咲子*; 田端 千紘; 齋藤 開*; 中島 多朗*; 日高 宏之*; 柳澤 達也*; 網塚 浩*
Journal of the Physical Society of Japan, 93(4), p.044701_1 - 044701_11, 2024/04
被引用回数：2 パーセンタイル：34.52(Physics, Multidisciplinary)We investigated the magnetic structure of the antiferromagnetic (AFM) ordered state ( 
34 K) in tetragonal UPtSi using polarized and unpolarized neutron diffraction. Previous neutron scattering studies reported that this system possesses a simple AFM structure with a propagation vector, Q= 0, and the ordered magnetic moments aligned along the c-axis. By contrast, our latest resonant X-ray scattering (RXS) experiments have revealed that the magnetic structure is modulated by the charge-density-wave (CDW) order, which emerges in one of the two Pt atomic layers in the unit cell below 320 K. The modulation is characterized by a transverse wave in the c-plane, with the propagation vector of the CDW order, q
= (0.42, 0, 0). In this study using neutron scattering, we observed that the superlattice reflections specified by q develop below , in addition to the magnetic reflections with Q= 0, thereby further confirming the presence of modulation in the AFM structure of this system. From detailed analyses, we revealed that the amplitude of the transverse-wave magnetic modulation is 0.72(2)
/U, which is quantitative information that can not be obtained through RXS experiments. This implies that the CDW drives the ordered magnetic moments to be tilted up to 20
in the AFM state. The observations strongly suggest that the magnetism of UPtSi is heavily influenced by the hybridization effects between the 
electrons of U and the 5d electrons of Pt.
Pt
Ga
studied by resonant X-ray and neutron scattering田端 千紘; 今 布咲子*; 太田 玖吾*; 日比野 瑠央*; 松本 裕司*; 網塚 浩*; 中尾 裕則*; 芳賀 芳範; 金子 耕士
Physical Review B, 109(13), p.134403_1 - 134403_7, 2024/04
被引用回数：3 パーセンタイル：32.00(Materials Science, Multidisciplinary)Antiferromagnetic (AF) order of UPtGa with the ordering temperature 
= 26 K was investigated by resonant X-ray scattering and neutron diffraction on single crystals. This compound possesses a unique crystal structure in which uranium ions form honeycomb layers and then stacks along the c-axis with slight offset, which gives rise to a stacking disorder. The AF order can be described with the propagation vector of q = (1/6, 1/6, 0) in the hexagonal notation. The ordered magnetic moments orient perpendicular to the honeycomb layers, indicating a collinear spin structure consistent with Ising-like anisotropy. The magnetic reflections are found to be broadened along c
indicating that the stacking disorder results in anisotropic correlation lengths. The semiquantitative analysis of neutron diffraction intensity, combined with group theory considerations based on the crystallographic symmetry, suggests a zig-zag type magnetic structure for the AF ground state, in which the AF coupling runs perpendicular to the stacking offset, characterized as q = (1, 0, 0). The realization of the zig-zag magnetic structure implies the presence of frustrating intralayer exchange interactions involving both ferromagnetic (FM) first-neighbor and AF second and third-neighbor interactions in this compound.
probed by static dc magnetization measurements清水 悠晴*; 芳賀 芳範; 柳澤 達也*; 網塚 浩*
Physical Review B, 93(2), p.024502_1 - 024502_8, 2016/01
被引用回数：9 パーセンタイル：36.27(Materials Science, Multidisciplinary)Static dc magnetization measurements were performed for a heavy fermion superconductor UBe single crystal. For the fields along the [100] and [110] directions of cubic lattice, a magnetic anomaly was found at a characteristic field 
within the superconducting mixed state. It was also found that magnetic anisotropy became more significant above this field. The present study shows that the thermodynamic property of superconductivity changes as a function of magnetic field.
清水 悠晴*; 橘高 俊一郎*; 榊原 俊郎*; 芳賀 芳範; 山本 悦嗣; 網塚 浩*; 堤 康雅*; 町田 一成*
Physical Review Letters, 114(14), p.147002_1 - 147002_6, 2015/04
被引用回数：35 パーセンタイル：81.06(Physics, Multidisciplinary)Low-energy excitation in the superconducting state of UBe were studied by means of specific-heat measurements in a rotating field. Quite unexpectedly, the magnetic-field dependence of specific heat is linear in field at low fields with an isotropic field-angle dependence. The observation implies that the gap is fully open over the Fermi surfaces, in contrast to the previous expectation.
松田 康弘*; Her, J.-L.*; 道村 真司*; 稲見 俊哉; 海老原 孝雄*; 網塚 浩*
JPS Conference Proceedings (Internet), 3, p.011044_1 - 011044_6, 2014/06
CeRhSiの放射光X線吸収実験を32Tまでのパルス強磁場下で行った。Ceの価数は5Kで3+よりわずかに大きく、20T以上の磁場印加に伴い減少する。磁場誘起の価数変化は磁化過程のメタ磁性転移に対応している。この現象は我々の以前に行ったCeRuSiの結果に似ており、Ce系重い電子系化合物に共通の現象と思われる。
清水 悠晴*; 芳賀 芳範; 柳澤 達也*; 網塚 浩*; 青木 大*; Brison, J.-P.*; Braithwaite, D.*
JPS Conference Proceedings (Internet), 3, p.015009_1 - 015009_6, 2014/06
Static DC magnetization measurements were performed in order to investigate magnetic response of the unconventional superconducting state of UBe. An unusual anomaly was observed inside the superconducting mixed state corresponding either to a peculiarity of superconducting diamagnetism or the anomalous vortex core structures.
Si田端 千紘*; 稲見 俊哉; 道村 真司*; 横山 淳*; 日高 宏之*; 柳澤 達也*; 網塚 浩*
Philosophical Magazine, 94(32-33), p.3691 - 3701, 2014/00
被引用回数：16 パーセンタイル：54.44(Materials Science, Multidisciplinary)We performed synchrotron X-ray diffraction measurements on a small single crystal of URuSi. A backscattering diffraction setup (2
) in combination with a Si(6 6 0) monochromator ensures a high instrumental resolution of 
, where 
denotes a lattice-plane spacing and 
is its spread expressed as the full width at half maximum (FWHM). We carefully measured the (5 5 0) Bragg peak in the temperature range between 5 and 25 K, and found it to show no signature of broadening and splitting when "Hidden Order (HO)" sets in below 17.5 K. Temperature variation of the peak position closely follows the behaviour of the known linear thermal expansion coefficient. Detailed analysis of the peak width reveals that the tetragonal fourfold rotational symmetry of URuSi is conserved in HO within the experimental accuracy of the orthorhombicity of 
.
by precise dc magnetization measurements清水 悠晴*; 芳賀 芳範; 池田 陽一*; 柳澤 達也*; 網塚 浩*
Physical Review Letters, 109(21), p.217001_1 - 217001_5, 2012/11
被引用回数：19 パーセンタイル：67.56(Physics, Multidisciplinary)Precise dc magnetization measurements were performed on a heavy fermion superconductor UBe. We observed a magnetic anomaly in the superconducting mixed state, implying an unusual superconducting state. The origin of the anomaly is discussed based on an unusual superconducting response or a peculiar normal-state magnetization at the vortex cores.
清水 悠晴*; 池田 陽一*; 若林 琢巳*; 芳賀 芳範; 天谷 健一*; 日高 宏之*; 柳澤 達也*; 網塚 浩*
Journal of the Physical Society of Japan, 80(9), p.093701_1 - 093701_4, 2011/09
被引用回数：9 パーセンタイル：51.58(Physics, Multidisciplinary)Low-temperature specific heat measurements under magnetic field were performed on a single crystal UBe. The specific heat shows a 
behavior below 0.7 
, where is the superconducting transition temperature, suggesting the existence of point nodes in the superconducting gap. Together with the isotropic behavior of the upper critical magnetic field, the symmetry of the Cooper paring is discussed.
Pd
Si柳澤 達也*; 立岩 尚之; 真山 太一*; 齋藤 旬*; 日高 宏之*; 網塚 浩*; 芳賀 芳範; 根本 祐一*; 後藤 輝孝*
Journal of the Physical Society of Japan, 80(Suppl.A), p.SA105_1 - SA105_3, 2011/07
被引用回数：3 パーセンタイル：26.05(Physics, Multidisciplinary)Ultrasonic measurements of UPdSi were performed in order to investigate elastic properties of the cage-structured compound UPdSi. At temperatures over antiferromagnetic ordering at = 19 K, neither an up-turn anomaly nor frequency dependence of the elastic constants, regarding the ultrasonic dispersion (UD), was found. A drastic change of 
mode at , in particular, implies a strong magneto-elastic coupling of 5
-electrons or a possible contribution of a ferroquadrupole interaction to the antiferromagnetism in UPdSi.
清水 悠晴*; 池田 陽一*; 若林 琢巳*; 天谷 健一*; 芳賀 芳範; 日高 宏之*; 柳澤 達也*; 網塚 浩*
Journal of the Physical Society of Japan, 80(Suppl.A), p.SA100_1 - SA100_3, 2011/07
被引用回数：1 パーセンタイル：10.62(Physics, Multidisciplinary)Low-temperature specific heat and static dc magnetization measurements have been performed in the superconducting state of the heavy-fermion compound UBe. The superconducting phase diagram was obtained from these measurements. We obtained Ginzburg-Landau parameter as a function of temperature and showed that a paramagnetic effect is present down to 0.5 K.
清水 悠晴*; 池田 陽一*; 若林 琢巳*; 天谷 健一*; 芳賀 芳範; 日高 宏之*; 柳澤 達也*; 網塚 浩*
Journal of Physics; Conference Series, 273, p.012084_1 - 012084_4, 2011/02
被引用回数：3 パーセンタイル：60.56(Physics, Condensed Matter)Static dc magnetization measurements in the superconducting mixed state of a single crystal UBe were performed by means of a capacitance Faraday-force method down to 0.24 K. Below the upper critical field 
, not only a peak effect but also an additional broad anomaly have been observed in magnetization curves. We report superconducting phase diagram of UBe obtained by our magnetization measurements, including these anomalies.
松田 康弘*; Her, J. L.*; 稲見 俊哉; 大和田 謙二; Ouyang, Z. W.*; 岡田 郷子*; 野尻 浩之*; 光田 暁弘*; 和田 裕文*; 吉村 一良*; et al.
Journal of Physics; Conference Series, 190, p.012019_1 - 012019_6, 2009/11
被引用回数：8 パーセンタイル：85.79(Physics, Condensed Matter)
-edge X-ray magnetic circular dichroism (XMCD) and X-ray absorption spectra (XAS) in several rare-earth elements have been studied in pulsed high magnetic fields up to 40 T. XMCD spectrum of Eu in EuNi(Si
Ge
) shows a characteristic two peak structure, reflecting the valence fluctuation. However, in YbInCu
, it is found that the XMCD spectrum of Yb shows only a single peak. In contrast to XMCD, two absorption bands in XAS are observed in both compounds. The intensity ratio between the two absorption bands changes significantly with increasing magnetic field in these materials, suggesting the field-induced valence change. The high magnetic field XMCD and XAS measurements have also been conducted in an antiferromagnetic heavy fermion compound CeRhSi. The Ce valence is found to be nearly trivalent and insensitive to magnetic field. The XMCD at Ce -edge increases rapidly around 26 T corresponding to the metamagnetic transition.
本間 徹生; 山本 悦嗣; 芳賀 芳範; 摂待 力生*; 荒木 新吾*; 稲田 佳彦*; 竹内 徹也*; 桑原 慶太郎*; 網塚 浩*; 榊原 俊郎*; et al.
Physica B; Condensed Matter, 281-282, p.195 - 196, 2000/06
被引用回数：2 パーセンタイル：15.00(Physics, Condensed Matter)われわれは六方晶AlB型結晶構造をもつ強磁性体UGaの5f電子状態を調べるために、磁気、弾性、伝導的特性とドハースファンアルフェン効果の実験を行った。これらの実験結果から六方晶の[0001]面内に100K以下で歪みが生じることを見いだした。これは、[1120]方向に向いた強磁性モーメントの発達によって引き起こされていると考えられる。
田端 千紘; 今 布咲子*; 網塚 浩*; 清水 悠晴*; 青木 大*; 中尾 裕則*
no journal, ,
Magnetic materials with no inversion center at the magnetic site have attracted much attention from the viewpoints of chiral magnetic orders and electromagnetic effects in recent years. URhSn has a crystal structure without spatial inversion symmetry (hexagonal, space group P-62m) consisting of distorted Kagome layers, and according to previous reports on polycrystalline samples, it undergoes a two-step phase transition at To = 54 K and TC = 16 K. While the low-temperature phase is considered a ferromagnetic phase with spontaneous magnetization along the c-axis, the order parameter of the high-temperature phase has remained unknown for decades. No symmetry breaking has been detected for this mysterious phase by microscopic measurements such as powder neutron diffraction and Mossbauer spectroscopy. We recently succeeded in growing high-quality single crystals of this compound and clarified its detailed bulk properties (specific heat, magnetization, electrical resistivity, and thermal expansion). Interestingly, the high-temperature phase below To isstabilized by a magnetic field parallel to the c-axis, despite the absence of a c-axis spontaneous magnetization component. This peculiar behavior indicates neither a simple ferromagnetic nor antiferromagnetic scenario. We investigated the order parameter of this unknown phase using a resonant X-ray scattering (RXS) technique. On the resonance condition at the M4 absorption edge of U, we observed a slight increase in the intensity of a fundamental Bragg reflection below To, suggesting an order parameter with q = 0 that does not break the translational symmetry of the crystal. The observed RXS signal can be interpreted by either case of order parameters of magnetic dipoles and electric quadrupoles. Given the Sn-Mossbauer and Sn-NMR reports of no internal magnetic field associated with the order, an electric quadrupolar order is more plausible.
