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Kitazawa Takafumi

Faculty of Science　Physics　Electronic Condensed Matter PhysicsAssistant Professor

Researcher basic information

■ Degree
  • Doctor of Science, Tohoku University, Mar. 2024
■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
  • 01002758
ORCID IDJ-Global ID■ Research Keywords and Fields
Research Field
  • Natural Science, Magnetism, superconductivity and strongly correlated systems

Career

■ Career
Career
  • Apr. 2026 - Present
    Hokkaido University, Faculty of Science, Assistant Professor, Japan
  • Apr. 2024 - Mar. 2026
    Japan Atomic Energy Agency, Advanced Science Research Center, Postdoctoral researcher, Japan
Educational Background
  • Apr. 2019 - Mar. 2024, Tohoku University, Graduate School of Science, Department of Physics, Japan
  • Apr. 2015 - Mar. 2019, Hiroshima University, Faculty of Science, Department of Physical Science, Japan

Research activity information

■ Papers
■ Lectures, oral presentations, etc.
  • Layer-confined spin fluctuations and in-plane incommensurate order in the van der Waals $5f$ magnet $\alpha$-UTe$_3$
    Sakai Hironori; Tabata Chihiro; Kaneko Koji; Tokiwa Yoshifumi; Kitazawa Takafumi; Kambe Shinsaku; Tokunaga Yo; Haga Yoshinori
    APS Global Physics Summit 2026, 19 Mar. 2026, English, Oral presentation
    15 Mar. 2026 - 20 Mar. 2026, Denver, United States, $\alpha$-UTe$_3$, a van der Waals (vdW) actinide compound, is a narrow-gap semiconductor with $5f$ moments. We reveal strongly anisotropic, layer-confined spin fluctuations below $\sim$20 K, with the $a$-axis component enhanced. Single crystal neutron diffraction finds an incommensurate ordering vector and a longitudinal sinusoidal modulation of $a$-axis moments with AFM stacking along $b$. This behavior can be understood within a crystal-electric-field (CEF) singlet-singlet induced-moment framework., [International presentation]
  • Determination of the hyperfine electron-nuclear level scheme in HoCo$_2$Zn$_{20}$
    Kitazawa Takafumi; Shimura Yasuyuki; Onimaru Takahiro; Tsuchida Shun; Kubo Katsunori; Haga Yoshinori; Sakai Hironori; Tokiwa Yoshifumi; Kambe Shinsaku; Tokunaga Yo
    APS Global Physics Summit 2026, 16 Mar. 2026, English, Oral presentation
    15 Mar. 2026 - 20 Mar. 2026, Denver, United States, We determined the electron-nuclear level scheme in the paramagnetic state of the holmium-based cubic compound HoCo$_2$Zn$_{20}$ using macroscopic thermodynamic probes alone. From magnetization and specific heat measurements, together with detailed analyses, we obtained the crystalline electric field (CEF) parameters, the magnetic exchange constant, and the hyperfine coupling constant between the $4f$ magnetic moment and the $^{165}$Ho nuclear spin. These refined parameters reveal that the $\Gamma_5$ CEF ground state is split by the hyperfine coupling, and that the sextet formed through coupling between the effective $S=1$ spin of the $f$ electrons and the $I=7/2$ spin of the $^{165}$Ho nucleus constitutes the paramagnetic ground state. Remarkably, the splitting energy width exceeds 1 K at zero magnetic field, underscoring the importance of electron-nuclear spin coupling in strongly correlated electron systems., 49523448;47279613, [International presentation]
  • None
    Araki Ryuhei; Hirose Yusuke; Haga Yoshinori; Kitazawa Takafumi; Tokunaga Yo; Settai Rikio*
    日本物理学会2026年春季大会, Japanese
    Mar. 2026, online, Japan, 本研究対象物質CeNiSb(Bi$_x$Sb$_{1-x}$)は、正方晶ZrCuSiAs型(空間群: $P4/nmm$)の構造を持ち、Ceサイトにおいて局所的に空間反転対称性の破れた構造を持つ。本研究ではCeNiSb(Bi$_x$Sb$_{1-x}$)の単結晶育成に初めて成功し、その電気抵抗率、比熱、磁化率測定を行った。Bi置換は格子定数$a$, $c$を増加させ、負の化学圧力効果をもたらす。物性測定の結果、$x = 0$で$T_\mathrm{N} = 0.8$ Kである反強磁性転移温度は$x$の増加に伴い高温側にシフトし、$x = 0.9$で$T_\mathrm{N} = 2.7$ Kに達することを明らかにした。この$T_\mathrm{N}$の増加は、負の化学圧力効果による$c$-$f$混成の抑制に伴い、系が量子臨界点近傍から局在磁性領域へシフトしたためと考えられる。, [Domestic Conference]
  • Structural transition in URh(Si,Ge) solid solutinos
    Haga Yoshinori; Tokiwa Yoshifumi; Sakai Hironori; Kitazawa Takafumi; Kambe Shinsaku; Tokunaga Yo
    日本物理学会2026年春季大会, Japanese
    Mar. 2026, online, Japan, URhSi及びURhGeはともにTiNiSi型結晶構造をとり、10K付近にキュリー点を持つ強磁性体である。両者の性質は類似しているが、URhGeのみが超伝導転移を起こす。本研究では、これらの系の固溶体を作成し、結晶構造を調べることにより、Si濃度80\%付近で構造相転移を起こし、RhとSi(Ge)が入れ替わるとともに、結合様式が変化することを見出した。また、キュリー温度も臨界濃度において不連続な変化を起こすことから、強磁性の特性も大きく変わっていることを明らかにした。, [Domestic Conference]
  • None
    Araki Ryuhei; Yokoyama Akira*; Kitazawa Takafumi; Haga Yoshinori; Hirose Yusuke; Settai Rikio*; Kimata Motoi; Tokunaga Yo
    学術変革領域研究(A)「アシンメトリが彩る量子物質の可視化・設計・創出」令和7年度領域全体会議・成果報告会, Japanese
    Jan. 2026, 名古屋, Japan, 本研究では集中イオンビーム(FIB)を用いた微細加工により、CeNi$_{1-y}$Bi$_2$の単結晶試料において、精密電気抵抗測定を行い、ゼロ磁場非相反伝導現象の有無を調べた。当日はその実験の詳細と結果について報告する。, [Domestic Conference]
  • Single crystals growth and physical properties in the heavy fermion systems CeNiSb$_2$ and CeNi$_2$Sb$_2$ with broken local-inversion symmetry
    Araki Ryuhei; Hirose Yusuke; Haga Yoshinori; Kitazawa Takafumi; Tokunaga Yo; Onuki Yoshichika; Settai Rikio
    JPS 80th Annual Meeting, 18 Sep. 2025, Japanese, Oral presentation
    16 Sep. 2025 - 19 Sep. 2025, 東広島, Japan, 本研究対象物質CeNiSb$_2$とCeNi$_2$Sb$_2$はそれぞれ局所空間反転対称性の破れたZrCuSi$_2$型構造とCaBe$_2$Ge$_2$構造をとり、いずれも正方晶P4/nmmの空間群を持つ。2つの構造はCe-Ni-Sbの積層が異なり、Niサイトの有無が構造を特徴づける。本研究では新たな手法でのCeNiSb$_{2}$の単結晶育成を実現した。またCeNi$_2$Sb$_2$の単結晶化に初めて成功し、$T_N$=1.5Kで磁気秩序を示すことを明らかにしたので、その詳細について報告する。, [Domestic Conference]
  • Incommensurate antiferromagnetic order of the Ising moment in $\alpha$-UTe$_3$
    Sakai Hironori; Tabata Chihiro; Kaneko Koji; Tokiwa Yoshifumi; Kitazawa Takafumi; Kambe Shinsaku; Tokunaga Yo; Haga Yoshinori
    日本物理学会第80回年次大会(2025年), 18 Sep. 2025, Japanese, Oral presentation
    16 Sep. 2025 - 19 Sep. 2025, 東広島, Japan, We investigated single crystals of the van der Waals compound $\alpha$-UTe$_3$ using microscopic techniques of nuclear magnetic resonance (NMR) and neutron diffraction. The conduction properties within the $ab$ plane exhibit semiconductor-like behavior, while the magnetism displays easy-plane anisotropy. NMR measurements were performed to clarify the anisotropy of magnetic fluctuations in the paramagnetic state, revealing a significant enhancement of antiferromagnetic fluctuations with spins aligned along the $a$ axis. Furthermore, although an antiferromagnetic transition occurs at $T_{\rm N}$ = 5K, the magnetic structure remained unclear. Neutron diffraction experiments were performed, yielding new insights into the magnetic structure. This presentation discusses the fundamental physical properties and magnetic characteristics of this compound., [Domestic Conference]
  • Investigation of the hyperfine interaction in HoCo$_2$Zn$_{20}$
    Kitazawa Takafumi; Haga Yoshinori; Sakai Hironori; Tokiwa Yoshifumi; Kambe Shinsaku; Tokunaga Yo
    JPS 80th Annual Meeting, 17 Sep. 2025, Japanese, Oral presentation
    16 Sep. 2025 - 19 Sep. 2025, 東広島, Japan, 結晶場基底状態が$\Gamma_5$三重項である立方晶のHo系化合物において、3チャンネル近藤効果の発現が理論的に提案されている。我々は、3チャンネル近藤効果を実験的に検証するため、$\Gamma_5$三重項の結晶場基底状態が提案されており、少なくとも1.85Kまで常磁性状態であることが報告されている立方晶のHoCo$_2$Zn$_{20}$を対象として、極低温物性測定を行ってきた。常磁性状態におけるHoサイトの基底状態を詳細に調べたところ、結晶場基底は確かに$\Gamma_5$三重項であるものの、各Hoサイトに存在する$I=7/2$の核スピンとf電子間の超微細相互作用により、結晶場基底準位は約1.3Kほどのエネルギー幅で分裂し、エネルギーの低い順に6重、8重、10重の擬縮退を形成していることが分かった。本講演では、それぞれの擬縮退がどのような固有状態で記述され、6重縮退がなぜ基底となるのか現象論的な観点から調べたので、その結果を報告する。, 47279613, [Domestic Conference]
  • Basic physical properties and precise ground state of HoCo$_2$Zn$_{20}$
    Takafumi Kitazawa; Yasuyuki Shimura; Takahiro Onimaru; Yoshinori Haga; Hironori Sakai; Yoshifumi Tokiwa; Shinsaku Kambe; Etsuji Yamamoto; Yo Tokunaga
    International Conference on Strongly Correlated Electron Systems 2025 (SCES 2025), 11 Jul. 2025, English, Oral presentation
    06 Jul. 2025 - 11 Jul. 2025, Montr\'eal, Canada, 47279613, [International presentation]
  • Determination of the hyperfine coupling constant in HoCo$_2$Zn$_{20}$ via thermodynamic measurements
    Kitazawa Takafumi; Shimura Yasuyuki*; Onimaru Takahiro*; Haga Yoshinori; Sakai Hironori; Tokiwa Yoshifumi; Kambe Shinsaku; Yamamoto Etsuji; Tokunaga Yo
    学術変革領域研究(A)「アシンメトリが彩る量子物質の可視化・設計・創出」トピカルミーティング「アシンメトリ量子物質の新展開; 多極子のスケールシームレス化に向けて」, Japanese
    Jun. 2025, 甲府, Japan, 極低温まで温度を下げても局在電子が秩序しない磁性体では、局在電子と核スピンの間ではたらく超微細相互作用の大きさ(超微細結合定数)が極低温における物性現象を理解する上で基礎的かつ重要な情報となる。本発表では、立方晶のホルミウム化合物HoCo$_2$Zn$_{20}$を対象に、比熱や磁化という巨視的な熱力学量測定のみで超微細結合定数を決定できることを提案する。具体的には、(1)比熱測定と数値計算による比熱の定量的比較、(2)比熱測定と磁化測定の組み合わせ、という2種類の手法を提案し、それぞれの手法で得られた超微細結合定数が定量的に一致することを示す。常磁性状態におけるHoサイトの基底状態は、超微細相互作用によって$\Gamma_5$三重項の結晶場基底とスピンの大きさ7/2の核スピンが結合した擬六重縮退であることが分かった。, [Domestic Conference]
  • Incommensurate antiferromagnetism in uranium-based van der Waals magnet $\alpha$-UTe$_3$
    Sakai Hironori; Tabata Chihiro; Kaneko Koji; Hirose Yusuke; Kitazawa Takafumi; Yamamoto Etsuji; Tokiwa Yoshifumi; Kambe Shinsaku; Tokunaga Yo; Haga Yoshinori
    11th International Workshop on the Dual Nature of f-Electrons 2025, English
    May 2025, Idaho Falls, In this study, a single crystal of uranium-based van der Waals compound $\alpha$-UTe$3$ was successfully grown. The structure features distinct Te sites, including a Te-Te bilayer, and a corrugated U network with U-U distances significantly exceeding the Hill limit, indicating a localized $f$-electron system. The material shows semiconducting in-plane transport and easy-plane magnetic anisotropy. An antiferromagnetic transition occurs at $T_{\rm N}$ = 5 K, but the magnetic structure was previously unknown. Neutron diffraction was performed to clarify the magnetic order, and this presentation discusses the compound's structural, electronic, and magnetic properties., [International presentation]
  • Magnetism in uranium-based van der Waals compound $\alpha$-UTe$_3$
    Sakai Hironori; Tabata Chihiro; Kaneko Koji; Kitazawa Takafumi; Yamamoto Etsuji; Tokiwa Yoshifumi; Kambe Shinsaku; Tokunaga Yo; Haga Yoshinori
    10th International Conference on Superconductivity and Magnetism (ICSM 2025) and the 3rd International Conference on Quantum Materials and Technologies (ICQMT 2025), English
    Apr. 2025, Fethiye, Turkey, In this study, we successfully grew a single crystal of the uranium-based van der Waals compound $\alpha$-UTe$_3$. The crystal structure includes a Te-Te bilayer composed of Te(2) and Te(3) atoms. The U and Te(1) atoms are between the double Te layers. The shortest U-U distance exceeds the Hill limit of $\sim$3.5 \AA. Therefore, one expects this compound to be regarded as the localized $f$ electron system. The conduction properties within the $c$-plane exhibit semiconducting behavior, and the magnetism demonstrates easy-plane anisotropy. An antiferromagnetic transition occurs at $T_{\rm N}$ =5 K; however, the magnetic structure remains undetermined. We conducted neutron diffraction experiments to elucidate the magnetic structure and address this. This presentation will discuss this compound's fundamental physical and magnetic properties., [International presentation]
  • Basic physical properties of single crystalline HoCo$_2$Zn$_{20}$
    Takafumi Kitazawa; Yasuyuki Shimura; Takahiro Onimaru; Yoshinori Haga; Hironori Sakai; Yoshifumi Tokiwa; Shinsaku Kambe; Etsuji Yamamoto; Yo Tokunaga
    JPS 2025 Spring Meeting, 19 Mar. 2025, Japanese, Oral presentation
    18 Mar. 2025 - 21 Mar. 2025, online, Japan, 47279613, [Domestic Conference]
  • Magnetism in $\alpha$-UTe$_3$
    Sakai Hironori; Tabata Chihiro; Kaneko Koji; Hirose Yusuke; Kitazawa Takafumi; Yamamoto Etsuji; Tokiwa Yoshifumi; Kambe Shinsaku; Tokunaga Yo; Haga Yoshinori
    学術変革領域研究(A)「アシンメトリが彩る量子物質の可視化・設計・創出」トピカルミーティング「精密計測$\times$アシンメトリ量子物質; アシンメトリ量子物性の深化に向けて」, 10 Feb. 2025, Japanese, Poster presentation
    09 Feb. 2025 - 10 Feb. 2025, 東海, Japan, We have investigated the magnetic properties of a single crystal of a uranium-based van der Waals compound $\alpha$-UTe$_3$ through the measurements of macroscopic physical properties and neutron scattering experiments. Based on the experimental results, we would like to discuss the magnetic properties of this compound., [Domestic Conference]
  • Basic physical properties of single crystalline HoCo$_2$Zn$_{20}$
    Takafumi Kitazawa
    学術変革領域研究(A)「アシンメトリが彩る量子物質の可視化・設計・創出」トピカルミーティング「精密計測 × アシンメトリ量子物質; アシンメトリ量子物性の深化に向けて」, 10 Feb. 2025, Japanese, Poster presentation
    09 Feb. 2025 - 10 Feb. 2025, 47279613
  • Magnetism in uranium-based van der Waals compound UTe$_3$
    Sakai Hironori; Tabata Chihiro; Kaneko Koji; Kitazawa Takafumi; Yamamoto Etsuji; Tokiwa Yoshifumi; Kambe Shinsaku; Tokunaga Yo; Haga Yoshinori
    JPS 79th Annual Meeting, 18 Sep. 2024, Japanese
    16 Sep. 2024 - 19 Sep. 2024, 札幌, Japan, Single crystals of the uranium-based van der Waals compound UTe$_3$ were grown. Neutron diffraction experiments were carried out to determine its magnetic structure. This compound's physical and magnetic properties will be reported., [Domestic Conference]
  • Crystal structure and low-temperature properties of uranium-containing Tsai-type approximant Al-Au-U
    Haga Yoshinori; Tokiwa Yoshifumi; Sakai Hironori; Kitazawa Takafumi; Yamamoto Etsuji; Kambe Shinsaku; Tokunaga Yo; Ikarugi Riko; Muro Yuji
    JPS 79th Annual Meeting, 18 Sep. 2024, Japanese
    16 Sep. 2024 - 19 Sep. 2024, 札幌, Japan, ウランを含むTsai型近似結晶Al-Au-Uの詳細な試料評価を行った。EPMA分析の結果をもとに組成の最適化を行ったところ不純物相をほとんど含まない単相試料の作成に成功した。これについてX線、中性子回折による構造評価と低温物性測定を行った結果を報告する。, [Domestic Conference]
  • Basic physical properties of single crystalline HoTr$_2$Zn$_{20}$ (Tr = Co, Rh, Ir)
    Kitazawa Takafumi; Haga Yoshinori; Sakai Hironori; Tokiwa Yoshifumi; Yamamoto Etsuji; Kambe Shinsaku; Tokunaga Yo
    JPS 79th Annual Meeting, 17 Sep. 2024, Japanese
    16 Sep. 2024 - 19 Sep. 2024, 札幌, Japan, 立方晶のHo系化合物で理論提案されている3チャンネル近藤効果の発現を検証するため、HoTr$_2$Zn$_{20}$ (Tr=Co, Rh, Ir)の単結晶において磁化・比熱・電気抵抗率の低温測定を行った。磁化の磁気異方性から結晶場解析を行った結果、いずれのTrの系においても結晶場基底状態は$\Gamma_5$三重項となった。また、磁化の温度変化に加えて、比熱と電気抵抗率の温度変化を測定した結果、少なくとも1.8Kまで温度を下げても転移を示唆する振る舞いは見られなかった。これらの結果は、HoTr$_2$Zn$_{20}$が3チャンネル近藤効果の発現候補物質であることを示唆している。, 47279613, [Domestic Conference]
  • Pulsed high magnetic field measurements in a quasi-degenerate diluted Yb system (Lu,Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Ikeda Yoichi; Matsuo Akira; Imajo Shusaku; Shimizu Yusei; Kawamata Masahiro; Tokunaga Yo; Haga Yoshinori; Opletal P.; Sakai Hironori; Tokiwa Yoshifumi; Yamamoto Etsuji; Kambe Shinsaku; Kohama Yoshimitsu; Kindo Koichi; Fujita Masaki
    22nd International Conference on Magnetism (ICM 2024), 02 Jul. 2024, English, Oral presentation
    30 Jun. 2024 - 05 Jul. 2024, Bologna, Italy, A diluted Yb system (Lu,Yb)Rh$_2$Zn$_{20}$ is an impurity Kondo alloy with quasi-octet degeneracy due to strong $c$-$f$ hybridization. In addition to the large degeneracy of $N = 8$, we found field-induced single-ion magnetic anisotropy above about 5 T, which cannot be explained by the existing Kondo model. To understand the $f$-electron state under magnetic fields, where the magnetic anisotropy develops, we measured the magnetization and specific heat of the diluted Yb system (Lu,Yb)Rh$_2$Zn$_{20}$ under pulsed high magnetic fields. The magnetization curves coincided between the processes of increasing and decreasing magnetic fields. This indicates that eddy-current heating is sufficiently suppressed, and isothermal magnetization curves can be measured. The magnetic easy and hard axes along the $\langle 100 \rangle$ and $\langle 111 \rangle$ directions, respectively, remained unchanged even above the Kondo crossover field of 22.7 T, where the $f$-electrons are localized. The field dependence of the electronic specific heat coefficients, estimated from the specific heat measurements, increased to about 1 J Yb-mol$^{-1}$ K$^{-2}$ and decreased around the Kondo crossover field. The decreasing electronic specific heat coefficients at the Kondo field suggest the localization of the $f$-electrons. In addition, the anisotropic magnetic response was observed not only in magnetization but also in specific heat measurements., [International presentation]
  • Physical properties of uranium containing Tsai-type approximant
    Haga Yoshinori; Tokiwa Yoshifumi; Sakai Hironori; Kitazawa Takafumi; Yamamoto Etsuji; Kambe Shinsaku; Tokunaga Yo; Muro Yuji
    11th International Conference on Aperiodic Crystals (Aperiodic 2024), English
    24 Jun. 2024 - 28 Jun. 2024, Caen, France, We have investigated existence of a uranium-based Tsai-type cluster to verify the metallurgical stability and difference in the electronic properties from the isostructural rare earth systems. Physical properties were investigated by measuring magnetization, resistivity, and specific heat. The present results highlight characteristic features of 5f electronic states, contrasting with isostructural rare-earth systems., [International presentation]
  • Pulsed high field magnetization measurements in single crystals of the diluted Yb system (Lu, Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Tokunaga Yo; Haga Yoshinori; Opletal Petr; Sakai Hironori; Tokiwa Yoshifumi; Yamamoto Etsuji; Kambe Shinsaku
    JPS 2024 Spring Meeting, 19 Mar. 2024, Japanese, Oral presentation
    18 Mar. 2024 - 21 Mar. 2024, online, Japan, Yb希薄系(Lu,Yb)Rh$_2$Zn$_{20}$は、擬8重縮退の近藤一重項を形成する不純物近藤系である。単結晶を用いて強磁場磁化測定を行った結果、既存の近藤モデルでは説明できないYb単サイトで発言する磁場有機の磁気異方性が現れ、強磁場まで維持されることがわかった。, [Domestic Conference]
  • Microscopic observation of the multiorbital Kondo effect in the heavy-fermion compound YbRh$_2$Zn$_{20}$
    Takafumi Kitazawa
    FY2023 Quantum Beam Science Festa, 06 Mar. 2024, Japanese, Invited oral presentation
    06 Mar. 2024 - 06 Mar. 2024, Mito, Japan, [Invited], [Domestic Conference]
  • Specific heat measurements under magnetic fields in a quasi-degenerate Kondo alloy (Lu,Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Ikeda Yoichi; Shimizu Yusei
    IMR-Oarai & Alpha Workshop, 28 Sep. 2023, Japanese, Oral presentation
    27 Sep. 2023 - 29 Sep. 2023, Tokyo Office, Tohoku University, Japan, [Domestic Conference]
  • Anisotropic electric transport in UOX(X = S, Se, Te)
    Petr Opletal; Hironori Sakai; Yoshinori Haga; Yoshifumi Tokiwa; Etsuji Yamamoto; Takafumi Kitazawa; Shinsaku Kambe; Yo Tokunaga
    JPS 78th Annual Meeting, 18 Sep. 2023, English, Oral presentation
    16 Sep. 2023 - 19 Sep. 2023, Sendai, Japan, [Domestic Conference]
  • Investigation of the multiorbital Kondo effect in a uranium compound Lu$_{1-x}$U$_x$Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Tokunaga Yo; Haga Yoshinori; Opletal Petr; Sakai Hironori; Tokiwa Yoshifumi; Yamamoto Etsuji; Kambe Shinsaku; Ikeda Yoichi; Fujita Masaki
    JPS 78th Annual Meeting, 18 Sep. 2023, Japanese, Oral presentation
    16 Sep. 2023 - 19 Sep. 2023, Sendai, Japan, ウラン化合物希釈系Lu$_{1-x}$U$_x$Rh$_2$Zn$_{20}$において、縮重度の大きな近藤効果の発現を検証した。母物質のURh$_2$Zn$_{20}$は重い電子系物質であり、磁化率が9Kで極大を示し、縮重度の大きな近藤効果の実現が示唆されていた。ウランを13\%まで希釈した試料を作製し、磁化測定を行った結果、磁化率の極大は消失し、縮重度の大きな近藤効果が実現してないことを示唆している。同型のYb化合物とは大きく異なることがわかった。, [Domestic Conference]
  • Investigation of the multiorbital Kondo effect in a 5f-electron compound (Lu,U)Ru$_2$Zn$_{20}$
    Kitazawa Takafumi; Tokunaga Yo; Haga Yoshinori; Opletal Petr; Sakai Hironori; Tokiwa Yoshifumi; Yamamoto Etsuji; Kambe Shinsaku; Ikeda Yoichi; Fujita Masaki
    International Conference on Strongly Correlated Electron Systems 2023 (SCES 2023), 03 Jul. 2023, English, Poster presentation
    02 Jul. 2023 - 07 Jul. 2023, Incheon, Korea, Republic of, Possible multiorbital Kondo effect occurring in URh$_2$Zn$_{20}$ is examined by diluting with non-magnetic Lu. An experimental signature of a local maximum in magnetic susceptibility $\chi(T)$ disappeared in the diluted Lu$_{1-x}$U$_x$Rh$_2$Zn$_{20}$, suggesting that the anomaly in $\chi(T)$ can be attributed to intersite correlation effects rather than the single-site property., [International presentation]
  • Multiorbital Kondo Effect in Diluted f-electron Systems
    Takafumi Kitazawa
    The 10th International Workshop on the Dual Nature of f-Electrons, 29 Jun. 2023, English, Invited oral presentation
    26 Jun. 2023 - 29 Jun. 2023, Himeji, Japan, [Invited], [International presentation]
  • Investigation of the Multiorbital Kondo Effect in Uranium Compounds (Lu,U)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Tokunaga Yo; Haga Yoshinori; Petr Opletal; Sakai Hironori; Tokiwa Yoshifumi; Yamamoto Etsuji; Kambe Shinsaku; Ikeda Yoichi; Fujita Masaki
    The 144th IMR Lecture Meeting, 30 May 2023, Japanese, Poster presentation
    30 May 2023 - 30 May 2023, Institute for Materials Research, Tohoku University, Japan, [Domestic Conference]
  • High magnetic field specific heat of a quasi-degenerate Kondo alloy (Lu, Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Ikeda Yoichi; Imajo Shusaku; Haga Yoshinori; Kohama Yoshimitsu; Tokunaga Yo; Fujita Masaki
    JPS 2023 Spring Meeting, 23 Mar. 2023, Japanese, Oral presentation
    22 Mar. 2023 - 25 Mar. 2023, online, Japan, 表題の物質は、縮重度N=8の不純物近藤系と考えられている。強磁場下での磁化及び電子比熱測定により、近藤一重項に対する異方的な磁場応答を捉えることに成功した。, [Domestic Conference]
  • Pulsed high field measurements in quasi-degenerate diluted Yb systems (Lu,Yb)Rh$_{2}$Zn$_{20}$
    Takafumi Kitazawa; Yoichi Ikeda; Akira Matsuo; Shusaku Imajo; Yoshinori Haga; Yo Tokunaga; Koichi Kindo; Yoshimitsu Kohama; Masaki Fujita
    GIMRT, REIMEI and IRN Joint International Workshop on Superconductivity, Structural Complexity and Topology of UTe$_{2}$ and Aperiodic Crystals, 30 Nov. 2022, English, Poster presentation
    30 Nov. 2022 - 02 Dec. 2022, Sendai, Japan, Yb希薄系(Lu,Yb)Rh$_{2}$Zn$_{20}$は、基底状態として多重縮重の近藤一重項をとる不純物近藤系である。筆頭発表者は、この物質が近藤磁場よりも十分に低い磁場で磁気異方性が発達することを見出した。磁気異方性の発達過程を調べるため、現在、磁化および比熱のパルス強磁場実験を行っている。講演では、改良した磁化測定手法、および、比熱の磁気異方性を中心にパルス強磁場実験の進捗状況を発表する。, [International presentation]
  • Thermal expansion measurements in a diluted Yb system (Lu,Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Ikeda Yoichi; Shimizu Yusei; Fujita Masaki
    IMR-Oarai & Alpha Workshop, 29 Sep. 2022, Japanese, Poster presentation
    28 Sep. 2022 - 30 Sep. 2022, Institute for Materials Research, Tohoku University, Japan, [Domestic Conference]
  • Pulsed high field magnetization measurements in quasi-degenerate diluted Yb systems (Lu,Yb)Rh$_2$Zn$_{20}$
    Takafumi Kitazawa; Yoichi Ikeda; Akira Matsuo; Koichi Kindo; Masaki Fujita
    JPS 2022 Autumn Meeting, 13 Sep. 2022, Japanese, Oral presentation
    06 Sep. 2022 - 15 Sep. 2022, Tokyo, Japan, [Domestic Conference]
  • Relation between the lattice volume and characteristic temperatures in Yb-based multiorbital Kondo systems (R,Yb)Rh$_2$Zn$_{20}$ (R = Sc, Lu, and Y)
    T. Kitazawa; Y. Ikeda; Y. Shimizu; A. Matsuo; M. Yamashita; K. Kindo; M. Fujita
    29th International Conference on Low Temperature Physics, 23 Aug. 2022, English, Poster presentation
    18 Aug. 2022 - 24 Aug. 2022, Sapporo, Japan, [International presentation]
  • Relation between the lattice volume and characteristic temperatures in Yb-based multiorbital Kondo alloys (R,Yb)Rh$_2$Zn$_{20}$ (R = Sc, Lu, and Y)
    Kitazawa Takafumi; Ikeda Yoichi; Shimizu Yusei; Matsuo Akira; Yamashita Minoru; Kindo Koichi; Fujita Masaki
    The 142nd IMR Lecture Meeting, 24 May 2022, Japanese, Poster presentation
    24 May 2022 - 24 May 2022, online, Japan, [Domestic Conference]
  • Relation between the unit cell volume and characteristic temperatures in quasi-degenerate diluted Yb systems (R,Yb)Rh$_2$Zn$_{20}$ (R = nonmagnetic element)
    Takafumi Kitazawa; Yoichi Ikeda; Akira Matsuo; Minoru Yamashita; Koichi Kindo; Masaki Fujita
    JPS 77th Annual Meeting, 15 Mar. 2022, Japanese, Oral presentation
    15 Mar. 2022 - 19 Mar. 2022, online, Japan, [Domestic Conference]
  • Demonstration of the multiorbital Kondo effect in a Yb-based intermetallic compound (Lu,Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi
    Cutting-edge Research on Magnetic and Superconducting Materials Using Muons, 07 Jan. 2022, Japanese, Oral presentation
    07 Jan. 2022 - 08 Jan. 2022, Toyonaka Campus, Osaka University, Japan, [Domestic Conference]
  • Single-site metamagnetism originating from the Kondo effect in a diluted Yb system (Lu,Yb)Rh$_2$Zn$_{20}$
    Takafumi Kitazawa; Yoichi Ikeda; Akira Matsuo; Toshiro Sakakibara; Yusuke Nambu; Koichi Kindo; Masaki Fujita
    JPS 2021 Autumn Meeting, 23 Sep. 2021, Japanese, Oral presentation
    14 Sep. 2021 - 23 Sep. 2021, online, Japan, [Domestic Conference]
  • Single-site metamagnetism originating from the Kondo effect in a diluted Yb system (Lu,Yb)Rh$_2$Zn$_{20}$
    Kitazawa Takafumi; Ikeda Yoichi; Matsuo Akira; Sakakibara Toshiro; Nambu Yusuke; Kindo Koichi; Fujita Masaki
    The 140th IMR Lecture Meeting, 26 May 2021, Japanese, Poster presentation
    26 May 2021 - 26 May 2021, online, Japan, [Domestic Conference]
  • Magnetic fluctuations in the single-site metamagnetic system studied by inelastic neutron scattering experiments
    Kitazawa Takafumi
    Tohoku U-CROSS-JAEA joint seminar, 25 Feb. 2021, Japanese, Oral presentation
    25 Feb. 2021 - 25 Feb. 2021, online, Japan, [Domestic Conference]
  • Inelastic Neutron Scattering Study of Kondo Effect in Pseudo-multiplet Systems YbTr2Zn20 (Tr = Rh, Ir)
    Takafumi Kitazawa; Yoichi Ikeda; Kazuhiko Ikeuchi; Kazuya Kamazawa; Manabu Ohkawara; Masaki Fujita
    JSNS2020, 10 Nov. 2020, Japanese, Oral presentation
    09 Nov. 2020 - 11 Nov. 2020, online, Japan, [Domestic Conference]
  • Enhancement of the c-f hybridization in YbTr$_2$Zn$_{20}$ (Tr = Rh, Ir) revealed by inelastic neutron scattering experiments
    Takafumi Kitazawa; Yoichi Ikeda; Kazuhiko Ikeuchi; Kazuya Kamazawa; Manabu Ohkawara; Masaki Fujita
    JPS 2020 Autumn Meeting, 08 Sep. 2020, Japanese, Poster presentation
    08 Sep. 2020 - 17 Sep. 2020, online, [Domestic Conference]
  • Crystalline-electric-field levels in the Yb-diluted systems Y$_{1-x}$Yb$_x$T$_2$Zn$_{20}$ (T = Co, Rh)
    Kitazawa Takafumi; Ikeda Yoichi; Taniguchi Takanori; Fujita Masaki
    日本物理学会第75回年次大会(2020年), 16 Mar. 2020, Japanese, Oral presentation
    16 Mar. 2020 - 19 Mar. 2020, Nagoya, Japan, [Domestic Conference]
  • Identification of Kondo temperature and crystalline electric field level scheme in heavy-fermion compounds YbT$_2$Zn$_{20}$ (T = Co, Rh)
    Takafumi Kitazawa; Yoichi Ikeda; Masaki Fujita
    東北大金研-CROSS ワークショップ J-PARC と JRR-3 の相補利用による偏極中性子科学の新展開, Aug. 2019, Poster presentation
    Aug. 2019, Sendai, Japan, [Domestic Conference]
  • Approaching to a Quantum Critical Point in Super-Heavy-Fermion Compound YbCo$_2$Zn$_{20}$
    T. Kitazawa; Y. Shimura; S. Tsuda; S. Bachas; P. Gegenwar; Y. Yamane; K. Umeo; T. Onimaru; T. Takabatake; H. T. Hirose; N. Kikugawa; T. Terashima; S. Uji
    The Second International Workshop Emergent Condensed-Matter Physics ECMP2019, 19 Mar. 2019, English, Poster presentation
    18 Mar. 2019 - 20 Mar. 2019, Hiroshima, Japan, [International presentation]
■ Research Themes