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We report the magnetic properties of the double perovskites SrLaCuSbO6 (SLCSO) and SrLaCuNbO6 (SLCNO). The temperature dependence of the magnetic susceptibilities of both compounds shows a broad maximum characteristic of an S=1/2 square lattice Heisenberg antiferromagnet. Magnetic ordering occurs at TN=13.6 and 15.7 K for SLCSO and SLCNO, respectively. Neutron powder diffraction measurements reveal contrasting spin structures in both compounds. The spin structures of SLCSO and SLCNO below TN are Néel antiferromagnetic and columnar antiferromagnetic, respectively. This result demonstrates that the nearest-neighbor interaction is dominant in SLCSO, whereas the next-nearest-neighbor interaction is dominant in SLCNO. The magnitude of the ordered moment was evaluated at 3.5 K to be m=0.39(3)μB for SLCSO and 0.37(1)μB for SLCNO, which are significantly smaller than those calculated using linear spin wave theory. We infer that the small ordered moment is caused by the effect of bond randomness arising from the site disorder of Sr and La ions.

Low-Temperature magnetic properties were investigated on the gold nano particles (GNPs) with an average size of 11.5 nm, assembled with molecules of ruthenium complex (Ru0), and phenylboronic acid (B0) by the proton nuclear magnetic resonance (1H-NMR) and susceptibility measurements. The temperature dependence of the NMR shift and the uniform susceptibility was described as the sum of the Curie-Weiss term and a positive constant term. From the former, the average number of Ru0 on each GNP was estimated to be 118, which is 23% of the calculation. The finite positive constant term shows a clear contrast with the well-known fact that the bulk gold is diamagnetic. Finally, a disappearance of the motional narrowing effect in the proton NMR spectra below 60 K indicates that the wavering motion of Ru0 complexes on GNP at room temperature is frozen at low temperatures.

We have investigated the hyperfine coupling between Cs and Cr on the S = 3/2 equilateral triangular spin tube CsCrF4, utilizing 133Cs-NMR. At paramagnetic state above 80 K, we have obtained spectra containing a single peak, which reflects the single crystallographic Cs site. From the temperature dependence of the peak shift and peak width, we evaluated effective values of the isotropic and the anisotropic part of hyperfine coupling. The latter was compared with the calculated dipole contribution. Using obtained parameters with assumed spin structure, we tried to reproduce the broadened spectrum in the ordered state at 2.0 K. The preliminary analysis shows the 120-degree structure does not accord with the observed spectra at the ordered state.

© Published under licence by IOP Publishing Ltd. S = 1/2 competing spin chain compound Cs2Cu2Mo3O12 has two dominant exchange interactions of the nearest neighbouring ferromagnetic J 1 = 93 K and the second nearest neighbouring antiferromagnetic J 2 = +33 K, and is expected to show the nematic Tomonaga-Luttinger liquid (TLL) state under high magnetic field region. The recent theoretical study by Sato et al. has shown that in the nematic TLL state, the spin fluctuations are expected to be highly anisotropic, that is, its transverse component is suppressed. Our previous NMR study on the present system showed that the dominant contribution to nuclear spin relaxation comes from the longitudinal component. In order to conclude that the transverse component of spin fluctuations is suppressed, the knowledge of hyperfine coupling is indispensable. This article is solely devoted to investigate the hyperfine coupling of 133Cs-NMR site to prove that the anisotropic part of hyperfine coupling, which connects the nuclear spin relaxation with the transverse spin fluctuations is considerably large to be A an = +770 Oe/μB.

A Rb-NMR study has been performed on the quasi-one-dimensional competing spin chain Rb2Cu2Mo3O12 with ferromagnetic and antiferromagnetic exchange interactions on nearest-neighboring and next-nearest neighboring spins, respectively. The system changes from a gapped ground state at zero field to a gapless state at HC≃2T, where the existence of magnetic order below 1 K was demonstrated by a broadening of the NMR spectrum, associated with a critical divergence of 1/T1. In the higher-temperature region, T1-1 showed a power-law-type temperature dependence, from which the field dependence of the Luttinger parameter K was obtained and compared with theoretical calculations based on the spin nematic Tomonaga-Luttinger liquid (TLL) state.

We report single-crystal V-51 NMR studies on volborthite Cu3V2O7(OH)(2) center dot 2H(2)O, which is regarded as a quasi-two-dimensional frustrated magnet with competing ferromagnetic and antiferromagnetic interactions. In the 1/3 magnetization plateau above 28 T, the nuclear spin-lattice relaxation rate 1/T-1 indicates an excitation gap with a large effective g factor in the range of 4.6-5.9, pointing to magnon bound states. Below 26 T where the gap has closed, the NMR spectra indicate small internal fields with a Gaussian-like distribution, whereas 1/T-1 shows a power-law-like temperature dependence in the paramagnetic state, which resembles a slowing down of spin fluctuations associated with magnetic order. We discuss the possibility of an exotic spin state caused by the condensation of magnon bound states below the magnetization plateau.

We have investigated high-field TF-μ SR and 1H-NMR on the S = 1/2 three dimensional spin dimer system NH4CuCl3, which shows a magnetic order at TN = 1.29 K under zero field and the two-stepped plateaus in high field regions HC1 = 5.0 T - HC2 = 12.8 T and HC3 = 17.9 T - HC4 = 24.7 T. Both probes showed spectra containing multiple peaks corresponding to different hyperfine fields, demonstrating the existence of magnetically inequivalent dimers in a unit cell. In the slope-state field region H &lt HC1, the existence of magnetic order was confirmed by the splitting in some of the NMR peaks. The whole width of NMR and μ SR spectra increased with increasing field, and no drastic change in their profile was observed at HC1. This indicates that the change in the spin state is continuous on entering the plateau state, and that no liquid-solid transition of magnons takes place at the phase boundary.

NMR study has been performed on the quasi-one dimensional antiferromagnet BaCo2Si2O7, in which three inequivalent CoO4 tetrahedra, slightly tilted from one another, are linked at vertices to form a chain along the easy-axis c. In its magnetically ordered state at 3.6 K, 59Co-NMR spectra were measured in the field region up to 12 T. From the observed three distinct sets of quadrupolar-split peak groups, three different hyperfine fields at Co sites were determined. They are slightly tilted from c-axis and are all different both in magnitude and direction, which is in agreement with the non-collinear magnetic structure.

© Published under licence by IOP Publishing Ltd. S = 1/2 quasi one dimensional Heisenberg chain Cs2Cu2Mo3O12 has two dominant exchange interactions of the nearest-neig hbouring ferromagnetic J1 = -93 K and the second nearest-neighbouring antiferromagnetic J2 = +33 K. These competing interactions on the spin chain are expected to bring rich physics, such as frustration or nematic Tomonaga-Luttinger liquid (TL) phase. In order to investigate its ground state at zero and finite fields, we have performed 133Cs-NMR experiments under the wide range of magnetic field up to 14 T, and μ-SR at zero field. In low-field region, the existence of long range magnetic order was demonstrated below 2 K. In the higher field region between 7 T and the saturation field Hs = 9.15 T, no evidence for magnetic order was confirmed at finite temperatures.

© Published under licence by IOP Publishing Ltd. Quasi-one-dimensional S = 1/2 Heisenberg system Rb2Cu2Mo3O12 described by the J1 - J2 model with the nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic exchange interactions have been investigated by 87/85Rb-NMR under extended field range up to 18 T. From the thermal-activation-type temperature dependence of l/T1, opening of the spin excitation gap was confirmed under the low field below 2 T. With increasing the field, the system becomes gapless, and the gap opens again in the high field saturation region, where the field dependence of the gap size showed the coherent excitation of the neighbouring two spins.

<p>S=3/2三角スピンチューブCsCrF_4_は、正三角形の三本足スピンチューブであり、フラストレーションと低次元性の観点からその基底状態が注目されている。磁性原子の配置に着目するとかごめ三角格子と等価であることからcuboc構造をとる可能性も期待されていたが、最近、中性子回折実験によって低温では120°構造をとると報告されている。我々はF/Cs-NMRを用いてそのスピン状態を調べており、今回はF/Csそれぞれについての超微細結合定数の評価から、基底状態の磁気構造について議論する。</p>

We present the results of C-13 NMR experiments in an organic superconductor with localized Fe spins beta ''-(BEDT-TTF)(4)[(H3O)Fe(C2O4)(3)] center dot C6H5Br. We reveal the antiferromagnetic coupling between Fe d spins and pi spins, which creates an exchange field antiparallel to the external field direction at the pi electrons. In addition to the static effects of Fe spins, we show from the nuclear spin-lattice relaxation rate measurement that the magnetic fluctuations generated by Fe spins are suppressed at low temperatures and high magnetic fields. These conditions are suitable to stabilize the field-induced superconductivity by the field compensation mechanism. After the suppression of Fe-spin dynamics by a magnetic field of 19 T, we observed the underlying pi-electron contribution. We discuss a possible anomaly in the pi-electron system.

The two-legged spin ladder Cu(CO3)(0.5)(ClO4)(H2O)(0.5)(NH3)(2.5) consists of a rung formed by two Cu(II)'s and of a spacing molecule CO32- between each two rungs. The non-centrosymmetric shape of CO32- molecule brings a slight bond alternation along the leg, and hence the system can be considered as an alternating spin chain, which is confirmed so far by the temperature dependence of magnetic susceptibility. In order to investigate its spin state at low temperatures, we have performed experiments of H-1-NMR, magnetization and specific heat under wide range of magnetic field, and have found the critical diverging of longitudinal relaxation rate 1/T-1, the spectral broadening and the lambda-type anomaly in specific heat at T-N similar or equal to 3.4 K, indicating the existence of long range magnetic order. In paramagnetic state well above T-N, 1/T-1 showed a power-law temperature dependence, suggesting the realization of Tomonaga Luttinger liquid state.

The ground state of the frustrated equilateral triangular spin tube CsCrF4 is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by F-19-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120 degrees-type structure in ab-plane does not accord with the NMR spectra of ordered state.

<p>最近接に強磁性、次近接に反強磁性の交換相互作用がある1次元競合鎖系では飽和磁場付近でスピンネマチック(多極Tomonaga-Luttinger液体)が実現するとHikiharaらによって報告され、近年、SatoらによってそれをNMR緩和率T1測定により検証できるという理論が提唱された。そこで我々は1〜20Tの磁場範囲でRbのT1測定を行った。本報告では行ったNMR測定の結果について報告する。</p>

<p>これまで量子スピンダイマーの研究は、低温で一重項状態にある系で、磁場・圧力等で、マグノンを誘起しそのBECを調べるものであった。本研究では、Ru二核金属錯体（β－ジケトナト）Ruダイマーの配位子を入れ替えることで、異種価数のキャリヤドープを行うことなく、Ru原子の価数をチューニングし、一重項状態を破壊することを目指す。講演ではNMRで見た磁性の変化にも言及する。</p>

<p>今回，我々は単結晶PrT_2_Al_20_のNMR測定を行った．得られたNMRスペクトルを解析し，NQRで得られたパラメータとバンド計算の結果を用いてスペクトルを再現することに成功した．この系のナイトシフトは，Tサイトの違いによらず非磁性基底状態を持つ局在4f電子系に期待される振る舞いを示す．T = Nbの試料は低温まで相転移を示唆する振る舞いが見られない一方，T = Taの試料ではナイトシフト，核磁気緩和率に低温で相転移に伴うと考えられる異常が見られた．講演ではスペクトルの解析の詳細とPrT_2_Al_20_の磁気励起について議論したい．</p>

<p>価数揺らぎ超伝導機構の理論では、高圧下で磁場を加えるとCeの価数転移温度が有限温度まで上昇する可能性が指摘されている。そこで、18テスラの強磁場下でCeCu_2_Si_2_の高圧超伝導相のCu-NMRを行うことにより、Ceの磁場誘起価数転移の探索を行う。前回、5.4GPaで磁場誘起転移の兆候を捉えたので、より高い圧力下の実験結果を報告する。</p>

<p>1次元磁性体BaCo_2_Si_2_O_7_は、二価のCoイオンを含み、CoO_4_四面体がc軸方向に一次元鎖を形成していることが知られており、TN=21K以下で弱強磁性をともなったIsing型反強磁性体であるといわれている。さらに、容易軸に磁場印加すると、14T付近で大きな磁化ジャンプが見られ、これは大きな磁気異方性のためであると思われている。我々は、^29^Siと^59^CoのNMRで得られたスペクトル解析を用いて、ミクロな磁性について研究した。</p>

<p>ダイマー系量子スピン磁性体NH_4_CuCl_3_は、低温において、二段磁化プラトーを示すことが知られており、その原因に興味が持たれ、「三つの非等価ダイマーモデル」などが提唱されている。本報告では、プラトー領域を含む磁場中(〜8 T)のμSRとH-NMRによって測定した内部磁場の変化について報告する。</p>

In order to investigate the hyperfine coupling of three inequivalent 19F sites in the equilateral triangular spin-tube antiferromagnet CsCrF4, we have measured the temperature dependence of 19F-NMR Knight shift in the paramagnetic state above 20K. The hyperfine coupling constants for three F-sites were determined to be -0.170, 0.280 and -0.045 T/μB, and were found to be consistent with the observed spectra at 1.65K, where the system is possibly in the ordered state.

A new method utilizing the low energy muon spin rotation (mu SR) technique to investigate the spin structure within the surface layer of topological insulator has been proposed. In order to detect the spin polarization parallel with the surface, one applies a weak field B-par, which, by breaking the time reversal symmetry, is expected to induce a net magnetization perpendicular the surface. This will affect the profile of muon spin depolarization spectra. Preliminary measurements on the topological insulator Bi1.5Sb0.5TeSe2 with tetradymite structure are also shown.

Substituting effect of CF3 to the Ru-based binuclear complex [{Ru-III( acac)(2)}(2)(mu-OEt)(2)], in which S = 1/2 spin dimer takes the singlet ground state have been investigated by means of the magnetic susceptibility chi and the longitudinal nuclear spin relaxation rate T-1(-1) of H-1/F-19-NMR. In CF3-substituted complex [{Ru-III(fhma)(2)}(2)(chi-OMe)(2)], we have observed the prominent magnetic response both in chi and T-1(-1). This behavior is attributed to the slight change in the Ru valence state due to the substitution.

Quasi one dimensional antiferromagnet Cu3Mo2O9 consists of spin chains and inequivalent spin pairs clinging on them, and shows the magnetic order at T-N = 7.9 K. The local structure of tetrahedron formed by neighboring four spins suggests a non-collinear spin structure in the ordered state and hence the multiferroicity. We have performed Cu-NMR measurements at low temperatures below T-N and showed that the observed spectra are consistent with the report by the recent neutron elastic scattering experiments in that the chain site Cu has only an extremely small ordered moment.

Longitudinal-field muon spin-relaxation (LF-mu SR) measurements have been performed in a bond-randomness introduced quantum spin system, Tl1-xKxCuCl3 with x = 0.40, in which the appearance of a Bose glass (BG) phase adjacent to the Bose-Einstein condensation (BEC) phase of excited triplets is observed. In the zero-field limit below 500 G, LF-mu SR time spectra shows an exponential-like decay, and the muon spin-relaxation rate does not have a significant temperature dependence down to 25 mK. This indicates that spins fluctuate in time and in space, and that the spin system is not into a spin gapped state. It is suggested that the theoretically predicted gapped Mott insulating phase adjacent to the BG phase disappears in this case. This result obtained by microprobe LF-mu SR measurements is consistent with an indication deduced from the results of macroscopic magnetization measurements.