NMR study of Si-substitution effect for Al in PrTi2Al20


NMR Study of Magnetic Structure and Spin Dynamids in a-CoV2O6


NMR Study of Caged Compounds TmTr2Al20 (Tr = Ti, V)


51V-NMR study of charge order induced by cation order in -Ag2/3V2O5


μSR study of A-site ordered perovskite manganite LaBaMn2O6


μSR investigation of magnetically ordered states in A-site ordered perovskite manganites RBaMn2O6 (R = Y and La)

Physical Review B, Condensed Matter and Materials Physics


51V NMR study of antiferromagnetic state and spin dynamics in quasi-one-dimensional BaCo2V2O8


NMR determination of noncollinear antiferromagnetic structure in TbCoGa5


Magnetic structure and spin dynamics of the quasi-one-dimensional spin-chain antiferromagnet BaCo2V2O8


7Li Spin-Lattice Relaxation at Low Temperatures in a Superionic Conductor β-LiGa

In order to investigate the Li+ ionic diffusion and the electronic states in a mixed conductor $eta$-LiGa with high Li+ ionic diffusibility and electron/hole conductivity, 7Li NMR linewidth and spin lattice relaxation measurements have been performed in 44.0, 47.0, and 50.0 at. % Li $eta$-LiGa samples at 10.03 MHz in the temperature range between 10 and 320 K. The onset temperature $T_{ext{MN}}=70$ K of the motional narrowing in 50.0 at. % sample has been determined from the temperature dependence of the linewidth. The Li+ ionic diffusion is found to contribute to the spin lattice relaxation rate $1/T_{1}$ down to ${im}0.5T_{ext{MN}}$ even below $T_{ext{MN}}$ where the motional narrowing does not occur. The high diffusibility of Li+ ions has been proved from a microscopic point of view. At low temperatures, the relations $1/T_{1}T=3.5imes 10^{-4}$, $3.8imes 10^{-4}$, and $5.1imes 10^{-4}$ s-1 K-1 are observed in 44.0, 47.0, and 50.0 at. % Li samples, respectively. The density of states of conduction electrons at the Fermi level in these compounds becomes higher with increasing Li content, which is consistent with the predictions by band calculations.

Journal of the Physical Society of Japan


11B NMR Study on rare earth ternary borides RRuB2


Trimer V3+ Spin Singlet State and Pseudo Gap in LiVS2 Studied by 51V and 7Li Nuclear Magnetic Resonance

To clarify the electronic state in a two-dimensional triangular lattice LiVS2, we have performed 51V- and 7Li-NMR measurements. Below the phase transition temperature $T_{ext{c}}$ of about 310 K from the paramagnetic state to a nonmagnetic state, the Knight shift of both 51V and 7Li does not depend on temperature. The 51V and 7Li spin lattice relaxation rates $1/T_{1}$ show the exponential temperature dependence below $T_{ext{c}}$, which indicates a gap structure of the electronic state. These results are in agreement with a trimer singlet of V3+ spins below $T_{ext{c}}$. The increase in 7Li $1/T_{1}$ above $T_{ext{c}}$ indicates the existence of the pseudo gap and agrees with the increase in paramagnetic susceptibility with increasing temperature and with the small entropy change at $T_{ext{c}}$ compared with that in LiVO2.


Microscopic investigation of antiferromagnetic order in A-Site-Ordered Perovskite Manganite YBaMn2O6


Novel superconductivity at the magnetic critical point in heavy-fermion systems: a systematic study of NQR under pressure


Energy gap formation in the valence fluctuating compound CeIrSb probed by Sb NMR and NQR


Phase Separation in A-site Ordered Perovskite Manganite LaBaMn2O6 Probed by 139La and 55Mn NMR

139La- and 55Mn-NMR spectra demonstrate that the ground state of the A-site-ordered perovskite manganite LaBaMn2O6 is a spatial mixture of the ferromagnetic and antiferromagnetic regions, which are assigned to the metallic and the insulating charge ordered state, respectively. This exotic coexisting state appears below 200 K via a first-order-like formation of the antiferromagnetic charge ordered state inside the ferromagnetic metal one. The Mn spin-spin relaxation rate indicates that the ferromagnetic region coexisting with the antiferromagnetic one in LaBaMn2O6 is identical to the bulk ferromagnetic metal phase of the disordered form La0.5Ba0.5MnO3 in spite of the absence of A-site disorder. This suggests a mesoscopic rather than nanoscopic nature of the ferromagnetic region in LaBaMn2O6.


Phase diagram of antiferromagnetism and superconductivity in CeRhIn5: a study of 115In-NQR under pressure


Novel phase diagram of superconductivity and ferromagnetism in UGe2 : a 73Ge-NQR study under high pressure


Evidence for Uniform Coexistence of Ferromagnetism and Unconventional Superconductivity in UGe2: A 73Ge-NQR Study under Pressure


139La NQR Relaxation in a Superconductor La3Ir2Ge2

同構造の Ce 化合物，Ce3Rh2Ge2 (TN=7.5 K) および Ce3Ir2Ge2 における，Rh の Ir 置換による磁気秩序の消失は興味深い現象である．これらの系の基礎物性の解明には，4f 電子のない参照物質 La3Rh2Ge2 や La3Ir2Ge2 の研究も重要である．本論文では，139La NQR により，La3Ir2Ge2 の電子状態についての研究を行った．スペクトルは 2 本のピークよりなり，これがどの遷移に対応するかを議論した．次に，1/T1 を測定し，常伝導状態で 1/T1=4.06 T の関係を見出し，通常金属であると結論した．超伝導状態では，Tc=4.7 K の直下でコヒーレンスピークを示し，温度低下とともに，指数関数的に減少した．見積もられたエネルギーギャップは BCS 超伝導体の値とよく一致している．


Magnetic Criticality and Unconventional Superconductivity in CeCoIn5: Study of 115In-Nuclear Quadrupole Resonance under Pressure

We report the systematic evolution of the superconducting (SC) characteristics of the heavy-fermion (HF) superconductor CeCoIn_5 via nuclear-quadrupole-resonance (NQR) measurement under pressure (P). The application of P significantly suppresses the nuclear spin-lattice relaxation rate 1/T_1 that is dominated by antiferromagnetic (AFM) spin fluctuations (SFs) specific to a quantum critical point (QCP). It is demonstrated that the marked suppression of AFM SFs leads to a reduction in the SC energy gap or in the coupling strength of the Cooper pair. T_c, nevertheless, increases with increasing P due to the increase in HF bandwidth. This is expected to make the lifetime of quasi-particles sufficiently long.


11B NMR Study of Magnetism in RRh3B2 (R = La, Ce, Nd, Sm, Eu and Gd)

CeRh3B2 は小さな飽和磁気モーメント 0.38 μB にもかかわらず，高い磁気転移温度 115 K をもち，その磁気秩序の起源が関心を集めている．さまざまな研究がなされ，局在モーメントモデルが遍歴電子モデルよりも優位に立っているが，決定的な証拠は得られていない．最近，非常に質の高い単結晶試料が作製され実験が進められ，この系は再び脚光を浴びる事となった．ここに，我々も 11B NMR による実験データを新たに加え，また物質として，EuRh3B2 も加えて系統的な解析を行い，4f電子と伝導電子間の混成強度と磁性との関係を議論し，局在モーメントモデルの立場での解釈を示した．

Journal of the Physical Society of Japan


New superconducting and magnetic phases Emerge on the magnetic criticality in CeIn3


209Bi-NQR Investigation of the Non-magnetic Heavy-fermion Compound CeRhBi


La-NQR Probe of Strong-Coupling s-Wave Superconductivity in LaRu3Si2

価数揺動物質 CeRu3Si2 の基準物質として重要な LaRu3Si2 の電子状態を解明するため，139La NQR による研究を行った．常伝導状態では，スピン格子緩和率 1/T1 は温度に比例し，1/T1=0.18 T の関係が得られ，系は単純金属と考えられる．超伝導状態では，BCS 超伝導体の場合の温度依存性を示し，エネルギーギャップは 2Δ/kBTc = 5.5 と大きな値をもつことが分かった．これらのことから，LaRu3Si2 の比較的高い超伝導転移温度 ( 6.5 K ) は，高い伝導電子状態密度と，強い電子-フォノン結合によるものと考えられる．


Exotic superconductivity in the coexistent phase of antiferromagnetism and superconductivity in CeCu2(Si0.98Ge0.02)2 : A Cu-NQR study under hydrostatic pressure


Low-temperature magnetic order and spin dynamics in YbRh2Si2

Physical Review B, Condensed Matter and Materials Physics


Gapless Magnetic and Quasi-particles Excitations due to the Coexistence of Antiferromagnetism and Superconductivity in CeRhIn5 : 115In-NQR Study under Pressure


Anisotropic Spin Fluctuations in Heavy-Fermion Superconductor CeCoIn5: In-NQR and Co-NMR studies


Mixed Valence State in Ce and Yb Compounds Studied by Magnetic Susceptibility

CeRu3Si2 の帯磁率 χ を価数揺動物質であるいくつもの Ce 化合物や Yb 化合物と比較し，スピン揺動温度 Tsf を評価した．これらの系で χ T / C が T/ Tsf によくスケールすることから，CeRu3Si2 も価数揺動物質であることが改めて確認できた．これらの化合物の間の，低温帯磁率，電子比熱係数および超伝導特性をスピン揺動温度の違いで議論し，局在性の強いものほど低温帯磁率，電子比熱係数が大きく，超伝導になりにくいことについて考察した．


Magnetic susceptibility of CeRu3Si2 and a scaling effect in mixed-valence compounds

希土類元素 Ce の 4f 電子の遍歴性/局在性の生み出す多彩な現象は，関心を集めている．CeRu3Si2 の価数揺動状態を研究するため，8-300 K の温度範囲で帯磁率 χ を測定した．帯磁率は 100 K 以下では，ほぼ一定であるが，それ以上の温度では温度上昇とともに，少し増加する．この温度依存性を，典型的な価数揺動物質 CeSn3 と比較し，スピン揺動温度 Tsf を求めた．CeRu3Si2 は χ T / C が T/ Tsf によくスケールする，典型的な価数揺動物質であることが分かった．


Unconventional superconductivity in ferromagnetic UGe2: a 73Ge nuclear magnetic resonance/nuclear quadrupole resonance study


Coexistence of Antiferromagnetism and Superconductivity near the Quantum Criticality of the Heavy-Fermion Compound CeRhIn5


Evidence for Unconventional Strong-Coupling Superconductivity in PrOs4Sb12: An Sb Nuclear Quadrupole Resonance Study

We report Sb-NQR results which evidence a heavy-fermion (HF) behavior and an unconventional superconducting (SC) property in Pr(Os4Sb12 with T(c)=1.85 K. The temperature (T) dependence of nuclear-spin-lattice-relaxation rate, 1/T(1), and NQR frequency unravel a low-lying crystal-electric-field splitting below T0 approximately 10 K, associated with Pr3+(4f(2))-derived ground state. In the SC state, 1/T(1) shows neither a coherence peak just below T(c) K nor a T3-like power-law behavior observed for anisotropic HF superconductors with the line-node gap. The isotropic energy gap with its size Delta/k(B)=4.8 K seems to open up across T(c) below T(*) approximately 2.3 K. It is surprising that Pr(Os4Sb12 looks like an isotropic HF superconductor-it may indeed argue for Cooper pairing via quadrupolar fluctuations.


Exotic magnetism and superconductivity in Ge-substituted CeCu2Si2 : A Cu NQR study


YbRh2Si2: Spin fluctuations in the vicinity of a quantum critical point at low magnetic field


115In-NQR evidence for unconventional superconductivity in CeIn3 under pressure


Evidence for the Coexistence of Superconductivity and the Magnetic A-Phase in CeCu2Si2 Proved by Muon Knight Shift

Journal of the Physical Society of Japan


μSR Studies on Heavy Fermion Superconductors CeIrIn5 and CeCoIn5


Quasiparticle Excitation in the Superconducting Pyrochlore Cd2Re2O7 Probed by Muon Spin Rotation


Pressure-temperature phase diagram of antiferromagnetism and superconductivity in CeRhIn5 and CeIn3: 115In-NQR study under pressure

Physical Review B, Condensed Matter and Materials Physics


Pressure-induced anomalous magnetism and unconventional superconductivity in CeRhIn5: 115In-NQR study under pressure


Exotic superconducting phase in CeCu2Si2 close to antiferromagnetism: A Cu-NQR study under hydrostatic pressure


Coexistence of superconductivity and antiferromagnetism in the heavy-fermion superconductor CeCu2(Si1-xGex)2 probed by means of Cu nuclear quadrupole resonance : a test case for the SO(5) theory


Evolution from magnetism to unconventional superconductivity in a series of CexCu2Si2 compounds probed by Cu NQR


Si-NMR study of antiferromagnetic heavy-fermion compounds CePd2Si2 and CeRh2Si2


Ru NMR and NQR probes of the metamagnetic transition in CeRu2Si2