Takehito Nakano

Ibaraki University · Graduate School of Science and Engineering

The s-electrons of alkali metals loaded into regular nanospaces (nanocages) of zeolite crystals display novel electronic properties, such as a ferrimagnetism, a ferromagnetism, an antiferromagnetism, an insulator-to-metal transition, etc., depending on the kind of alkali metals, their loading density, and the structure type of zeolite frameworks. T...

Synchrotron-radiation-based M\"ossbauer absorption spectroscopy of $^{40}\mathrm{K}$ nuclei was performed. We investigated potassium nanoclusters arrayed in a porous crystal of sodalite. The nanoclusters exhibit antiferromagnetic (AFM) ordering below $$\simeq${}72$ K. The energy-domain $^{40}\mathrm{K}$ M\"ossbauer spectra were successfully obtaine...

We have performed electron spin resonance (ESR) studies of K_{4}^{3+} and (K_{3}Rb)^{3+} nanoclusters incorporated in powder specimens of aluminosilicate sodalite at several microwave frequencies between 9 and 34 GHz. The K_{4}^{3+} and (K_{3}Rb)^{3+} clusters are arrayed in a bcc structure and are known to show antiferromagnetic ordering below the...

Sodium clusters formed in the regular nanospace of sodalite (aluminosilicate zeolite) are known to show antiferromagnetic order without any magnetic elements. The clusters are arrayed in a body centered cubic structure. We have performed a neutron diffraction study and succeeded in detecting the magnetic Bragg peaks of the s-electron spins for the...

Potassium nanoclusters in aluminosilicate zeolite A shows ferromagnetic properties, although bulk metal of K is nonmagnetic. K clusters are prepared by adsorbing guest K atoms into the supercages (α cages) of dehydrated zeolite A, where supercages with the inside diameter of ∼ 11 Å are arrayed in a simple cubic structure. By the loading of guest K...

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It is known that the insulator-metal transition occurs upon loading guest Na atoms into cages of the zeolite low silica X (LSX). In this study, the metallic and insulating phases of this material were investigated by the muon spin rotation (μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{am...

Temperature dependences of NMR spectra have been observed for 23Na and 27Al in the metallic phase of Na-K form low silica X (LSX) zeolite loaded with potassium, where the condition of saturation is achieved with a loading level of 9.0 atoms per supercage and the paramagnetic moment contributes to the magnetism of the system beyond simple isolated s...

Magnetic phase diagram of alkali metal-loaded sodalite. The antiferromagnetic transition temperature T N changes systematically with the alkali species of the clusters formed in the cages.

It is known that an N-type ferrimagnetic order with the highest Curie temperature TC\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varvec{T_C}$$\end{document} of abou...

Na-K alloy clusters can be formed by loading guest K atoms into the cages of zeolite low-silica X (LSX), which contains both Na+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{doc...

We have performed a powder neutron diffraction study on CsO 2 , where the unpaired electron with s = 1/2 in the π* orbital of the O 2 ion is responsible for the magnetism. The magnetic reflections 0 1/2 0 and 0 1/2 1 were observed below the Néel temperature of about 10 K. An antiferromagnetic structure with a propagation vector of (0, 1/2, 0) and m...

We have performed a powder neutron diffraction study on CsO$_2$, where the unpaired electron with $s=1/2$ in the $\pi^*$ orbital of the O$_2^-$ ion is responsible for the magnetism. The magnetic reflections 0 $\frac{1}{2}$ 0 and 0 $\frac{1}{2}$ 1 were observed below the N\'{e}el temperature of about 10 K. An antiferromagnetic structure with a propa...

In order to study the effect of muonic-Li on the µ ⁻ SR spectrum for Li battery materials, the transverse field (TF) µ ⁻ SR spectra have been measured for natural Li metal and ⁶ Li metal samples in the temperature range between 5 and 300 K. Here, TF denotes the magnetic field perpendicular to the initial µ ⁻ spin polarization. For both samples, the...

To study an intrinsic self-diffusion coefficient of Li+ (DLiJ) in a battery anode material, spinel Li4Ti5O12, negative and positive muon spin rotation and relaxation (μ±SR) spectra were measured using a powder sample in a temperature range of 100–400 K. The implanted μ+ in this study locates at an interstitial site near the O2– ion to form an O–H l...

The superconducting (SC) gap structure appearing in systems with single Fermi surface (FS) is generally described by the single gap function with s- or d-wave symmetry. The organic superconductor λ-(BETS)2GaCl4 [BETS = (CH2)2S2Se2C6Se2S2(CH2)2] endeavors to examine a novel SC gap structure on the distorted single cylindrical FS. Here, we show an ex...

We have investigated the low-temperature magnetism of sodium superoxide (NaO$_{2}$), in which spin, orbital, and lattice degrees of freedom are closely entangled. The magnetic susceptibility shows anomalies at $T_{1}=220$ K and $T_{2}=190$ K, which correspond well to the structural phase transition temperatures, and a sudden decrease below $T_{3}=3...

Magnetic properties of Mott–Hubbard systems are generally dominated by strong antiferromagnetic interactions produced by the Coulomb repulsion of electrons. Although theoretical possibility of a ferromagnetic ground state has been suggested by Nagaoka and Penn as single-hole doping in a Mott insulator, experimental realization has not been reported...

(This is an open access paper.) The internal magnetic field in a sodium battery compound, i.e., the paramagnet Na 0.7 CoO 2 , was investigated with negative muon spin rotation and relaxation (μ − SR), and the result was compared with the results previously obtained with μ + SR. The majority of implanted μ − is captured on an oxygen nucleus, while μ...

In zeolite low-silica X (LSX), beta-cages with the inside diameter of approx 7 AA{} are arrayed in a diamond structure. Among them, supercages with the inside diameter of approx 13 AA{} are formed and arrayed in a diamond structure by the sharing of windows with the inside diameter of approx 8 AA{}. The chemical formula of zeolite LSX used in the p...

The lower critical field of type-II organic layered superconductor l-(BETS) 2 GaCl 4 has been estimated by magnetic measurements. The demagnetization factor of a needle-like sample shape has been taken into account for the measurements by applying the external field, parallel and perpendicular to the conducting plane. The lower critical field for t...

Alkali metal clusters with an unpaired electron can be periodically arranged in a body-centered cubic structure in sodalite, a type of aluminosilicate zeolite, to form a Mott insulator accompanied with an antiferromagnetic ordering. This system does not contain any magnetic elements and is a novel magnetic system in which the magnetic order is real...

The ground state of alkali metals when the particle size decreases from bulk to nanometric atomic clusters is inevitably accompanied by quantum effects that can suppress their pristine metallic state. We demonstrate that the metallic nature of rubidium clusters confined and arrayed in the framework of insulating low-silica X zeolite is preserved. T...

We have performed X-band electron spin resonance (ESR) measurements on a single crystal of the metallic chiral helimagnet CrNb3S6 from 3.5 to 180 K and for the external magnetic fields Hext, up to 4 kOe, perpendicular to the c axis (the helical axis of CrNb3S6). This field-crystalline configuration is expected to provide the chiral soliton lattice...

The lower critical field of type-II organic layered superconductor λ-(BETS) 2 GaCl 4 has been estimated by magnetic measurement. In this study, the demagnetization factor of a needle-like sample shape has been taken into account for the measurements by applying external field, parallel and perpendicular to the conducting plane. The lower critical f...

Polycrystalline rubidium superoxide (RbO 2 ) has been synthesized by using solution method followed by the reaction process under the cooling condition of-40 °C. X-ray Powder Diffraction (XRD) spectra showed that RbO 2 was successfully synthesized by this method. The magnetic susceptibility and pulsed muon spin relaxation (μSR) measurements were ca...

X-ray powder diffraction (XRPD), magnetic susceptibility and muon-spin relaxation (μSR) measurements were carried out to investigate lattice symmetries and magnetic properties of one of alkali-metal superoxides, RbO 2. Two structural transitions were observed around 170 and 100 K in conjunction with the appearance of anomalies in the magnetic susce...

Potassium metal was loaded into K-form zeolite low-silica X(LSX) under the loading pressure P up to 1.5 GPa. A ferromagnetism is observed at P≈ 0.9 GPa below 13 K. The loading density of K atom n is estimated to be ≈15 per cage at the ferromagnetic loading pressure, and the pressure-derivative loading density dn/dP has a remarkable peak ≈11GPa−1 at...

We report on the experimental results of magnetic susceptibility, specific heat, electron spin resonance (ESR), and high-field magnetization measurements on a polycrystalline sample of the spin-$1/2$ distorted honeycomb-lattice antiferromagnet Cu$_2$(pymca)$_3$(ClO$_4$). Magnetic susceptibility shows a broad peak at about 25~K, which is typical of...

Alkali superoxide CsO2 is one of candidates for the spin-1/2 one-dimensional (1D) antiferromagnet, which may be sequentially caused by an ordering of the pi-orbital of O2- molecule below TS ~ 70 K. Here, we report on the magnetism in powder CsO2 and high-magnetic field magnetization measurements in pulsed-magnetic fields of up to 60 T. We obtained...

The evolution of the electronic properties of guest Na and Rb atoms in a disordered deformable lattice is investigated for a series of guest-atom densities n. The quasi-two-dimensional host M7.8−δAl7.8Si8.2O32.0 (M=Na, Rb), known as zeolite P, is used. The Na system is a stubborn bipolaronic insulator to the maximum n of 1.03. In contrast, the Rb s...

Magnetodielectric properties of the tetragonal magnetic insulator Ba(TiO)Cu4(PO4)4 consisting of asymmetric Cu4O12 (square cup)olas have been investigated in a magnetic field along the [001] axis (B [001]), where a metamagnetic transition occurs at B c||[001] ~ 12T and 1.4K. Clear anomalies associated with the transition to the high-field phase are...

We report a $^{23}$Na spin-lattice relaxation rate, $T_1^{-1}$, in low-silica X zeolite. $T_1^{-1}$ follows multiple BPP-type behavior as a result of thermal motion of sodium cations in insulating material. The estimated lowest activation energy of 15~meV is much lower than 100~meV observed previously for sodium motion in heavily Na-loaded samples...

Muon-spin-relaxation (μSR) measurements in the transverse-field (TF) of 30 G were carried out from 7 K down to 1.8 K on the non-magnetic anion-based organic superconductor λ-(BETS)2GaCl4. The TF-μSR time spectrum showed a significant increase with the Gaussian-type damping behavior below the superconducting transition temperature TC = 5 K confirmin...

Rb metal was loaded into dehydrated Rb-form zeolite L. The loading density of Rb atoms per unit cell, n, was changed up to 7.1. A resonant optical absorption-reflection band is observed at ≈1.0 eV in all samples. A new reflection band appears at ≈1.7 eV for n > 5. The 1.0 and 1.7 eV bands are assigned to the respective excitations from 1s to 1p and...

Magnetic-ordered states of the pyrochlore iridates Nd2Ir2O7 (Nd227) and Sm2Ir2O7 (Sm227), showing metal-insulator transitions at 33 and 117 K, respectively, were studied by both the muon-spin-relaxation (μSR) method and density functional theory (DFT) calculations. A long-range magnetic ordering of Ir moments appeared in conjunction with the metal...

In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal, monopole, and quadrupole moments. So far, however, t...

Supplementary Figures 1-9, Supplementary Tables 1-3, Supplementary Notes 1-4 and Supplementary References

The layered Mn(II) phosphite (NH4)4[Mn4(PO3H)6] is prepared by ionothermal reaction of MnCl2·4H2O, H3PO3, and NH4F using 1-pentyl-3-methylimidazolium bromide ([pmim]Br) as the solvent (autoclave, 150 °C, 7 d, ≈70% yield).

A new layered manganese(ii) phosphite, |NH4|4[Mn4(PO3H)6] (JIS-10), has been synthesised via the ionothermal method by using 1-pentyl-3-methylimidazolium bromide ([Pmim]Br) as the solvent. JIS-10 is the first manganese phosphite with a Mn/P ratio of 2/3, whose layered framework is built by the alternate connection of Mn2O9 dimers and PO3H pseudo-te...

The electronic states of potassium- (K-) intercalated zigzag-type polycyclic aromatic (PLA) hydrocarbon [polyacene PLAs] Kx(PLAs) are studied for a series of the four smallest molecules: naphthalene (NN), anthracene (AN), tetracene (TN), and pentacene (PN), focusing on their 1:1 stoichiometric phases. Clear experimental differences are identified b...

Potassium metal was loaded into K-form zeolite L crystals which have one-dimensional (1D) main-channels with an inside diameter of approximate to 1 nm. The loading density of K atoms per unit cell, n, was changed from 0 to 9.6. Optical, electrical and magnetic properties were measured for the powders of K-loaded zeolite L crystals. A resonant optic...

We report a systematic nuclear magnetic resonance investigation of the 23Na spin-lattice relaxation rate, 1/T1, in sodium loaded low-silica X (LSX) zeolite, Nan/Na12-LSX, for various loading levels of sodium atoms n across the metal-to-insulator crossover. For high loading levels of n ≥ 14.2, 1/T1T shows nearly temperature-independent behaviour bet...

We have studied orbital dynamics in the spin liquid candidate Ba3CuSb2O9 using multifrequency electron-spin resonance. We prepared two high-quality single crystals. The crystal with a slight copper deficiency shows a structural phase transition at around 200 K due to the cooperative Jahn-Teller effect, accompanied with orbital ordering. In contrast...

We explore orbital dynamics in the spin liquid candidate Ba3CuSb2O9 using multi-frequency electron spin resonance. We prepared two high quality single crystals. The crystal with a slight copper deficiency shows a structural phase transition at around 200 K due to the cooperative Jahn-Teller effect, accompanied with orbital ordering. In contrast, th...

In a porous crystal of zeolite low-silica X (LSX), β-cages and supercages (cavities) are arrayed in a diamond structure, respectively. We loaded potassium metal into zeolite LSX which has a chemical formula of Na7.3K4.7Al12Si12O48 per β-cage (or supercage), and generated Na-K alloy clusters in β-cages and/or supercages. We have investigated the mag...

We report a systematic nuclear magnetic resonance investigation of the $^{23}$Na spin-lattice relaxation rate, $1/T_1$, in sodium loaded low-silica X (LSX) zeolite, Na$_n$/Na$_{12}$-LSX, for various loading levels of sodium atoms $n$ across the metal-to-insulator crossover. For high loading levels of $n \geq 14.2$, $1/T_1T$ shows nearly temperature...

Potassium metal was loaded into porous crystals of potassium-form maximum aluminum zeolite P (K-MAP), and optical absorption, electrical resistivity, and magnetic susceptibility measurements were performed. The average loading density of potassium atoms per GIS cage of zeolite P, n, was systematically changed up to 1.09. Optical absorption bands ar...

Crystal structures of sodium clusters incorported in LSX zeolite [Na12Al12Si12O48 (Z = 8)] with FAU-type topology are analyzed by power X-ray diffraction. The two different Na-loaded samples, Na-9.4/Na-12-LSX and Na-16.7/Na-12-LSX show insulating and metallic states, respectively. The insulating state is changed to the metallic state upon increasin...

High quality bulk samples of anthracene (AN) doped with potassium (K) in 1 : 1 and 2 : 1 stoichiometries were successfully prepared by a method involving a room temperature solid-state mechanical diffusion process prior to intercalation reactions during heat treatment, and their physical properties were studied using both magnetic and optical measu...

We present a comprehensive structural study on perovskite-type 6H-Ba3CuSb2O9, which exhibits a spin-orbital short-range ordering on a honeycomb-based lattice. By combining synchrotron x-ray diffraction, electron spin resonance, ultrasound measurement and Raman spectroscopy, we found that the static Jahn-Teller distortion is absent down to the lowes...

Alkali metal nanoclusters can be stabilized in the regular cages of zeolite crystals by the loading of guest alkali metals. Cages are connected by the sharing of windows of the framework, and arrayed in simple cubic, diamond and body centered cubic structures in zeolites A, X and sodalite, respectively. The s-electrons have the localized nature of...

Zeolite LSX (low-silica X) crystals have an aluminosilicate framework with regular supercages and β-cages. They are arrayed in a double diamond structure. The loading density of guest K atoms per supercage (or β cage), n, can be controlled from 0 to ≈ 9. At n < 2, samples are nearly nonmagnetic and insulating. The Curie constant has a clear peak at...

We prepared Rb-rich K-Rb alloy nanoclusters arrayed in the regular nanospace of aluminosilicate sodalite which has a bcc arrangement of cages. The average chemical formula of the cluster is (K1.5Rb2.5)3+, where one unpaired s-electron is shared by four alkali cations and is confined in a cage. The magnetic susceptibility and the electron spin reson...

We investigated the annealing effects on the physical properties of SrFe$_2$(As$_{1-x}$P$_x$)$_2$ ($x=0.35$). The superconducting transition temperature ($T_c$) increased from 26 K to 33 K by annealing. The X-ray diffraction measurement suggested that the annealed crystals have the shorter/longer $a/c$-axes and the larger pnictogen height $h_\mathr...

Intercalated compounds of polycyclic aromatic hydrocarbons have been drawing much attention from the view point of new type of organic superconductors. The mechanism of superconductivity in these materials is still unclear, and therefore the true ground states with various carrier concentrations must be understood. The antiferromagnetic ground stat...

We report a \^{23}Na and \^{27}Al nuclear magnetic resonance (NMR) investigation of low-silica X (LSX) zeolite with chemical formula Na_{12}Al_{12}Si_{12}O_{48} (Na_{12}-LSX) loaded with n additional guest sodium atoms. Na_{n}/Na_{12}-LSX exhibits an insulator-to-metal transition around n=11.6, which is accompanied by a significant enhancement of b...

27Al NMR property of rubidium-loaded potassium-type sodalite, which has antiferromagnetic transition temperature TN of 80K, is reported. Similar to the case of potassium-loaded case, monotonous narrow spectrum is seen above TN and broadened one is observed below TN. Separately shifted component, which is seen in the case of sodium-loaded case, is n...

Electrical resistivity was measured for Na-doped low-silica X (LSX) zeolite at various Na-loading densities. Many s-electrons are introduced into the regular array of zeolite nanocages by the loading of guest Na atoms. The average Na-loading density per unite cage, n, was changed from 0 to ≈12≈12. Nonmagnetic and insulating properties are observed...

From the magnetization and magnetoresistance measurements, we constructed the magnetic phase diagram of Yb2Pt2Pb with the Shastry-Sutherland lattice, which consists of characteristic two phases below 1 K with many metamagnetic transitions, revealing magnetic frustrations.

Aluminosilicate zeolites are nanoporous crystals that make it possible to generate regularly arrayed alkali-metal nanoclusters by loading guest alkali atoms. Various kinds of magnetic orderings have been found in these materials depending on the host zeolite structure, the species of the guest alkali element, and the loading density. We have develo...

In this article, we have developed pressure loading technique to extend the loading density of guest alkali metals in nanoporous crystals of zeolites. Zeolite crystals have solid framework and open regular nanospace. In the nanocages of zeolite crystals, s-electrons provided by the guest alkali metals occupy quantum electronic states of clusters su...

Magnetoelectric (ME) properties were investigated for an XY-like spin glass (SG) system, Ni{x}Mn{1-x}TiO{3} with an ilmenite structure. The ME effect is usually observed in systems with peculiar couplings between a crystal lattice and a magnetic order. Nonetheless, we found an antisymmetric ME effect with nonzero ME tensor elements below T{ME}=8-10...

Na43+ and K43+ clusters arrayed in aluminosilicate sodalite are known to show antiferromagnetism below respective Néel temperatures TN=48 and ~=70 K. We newly prepared K-Rb alloy (K3Rb)3+ clusters in addition to Na43+ and K43+ ones, and performed muon-spin relaxation (muSR) measurements. We find a large amplitude of precession signal in zero-field...

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Na concentration (x) dependence of ferrimagnetic properties is investigated for Na–K alloy clusters incorporated in low-silica X (LSX) zeolite. In the LSX zeolite, β-cages of inner diameter ≈7 Å are arranged in a diamond structure, and supercages of inner diameter ≈13 Å are formed among them. The used LSX zeolite contains xNa+ and (12−x)K+ cations...

We have carried out electron spin resonance (ESR) measurements on powder samples of sodalite loaded with Na at several frequencies between 9.7 and 35GHz and at temperatures between 1.5 and 60K. The ESR absorption spectrum below a Néel temperature TN turns into an asymmetric spectrum with a long tail at low fields from a symmetric one above TN. The...

Optical and magnetic properties are investigated for low-silica X (LSX) zeolite loaded with Na metals at various loading densities. In LSX, β-cages with the inside diameter of ∼7Å are arrayed in a diamond structure and the supercages with that of ∼13Å are formed among them. When the average number of guest Na atoms per β cage, n, is smaller than ∼2...

27Al NMR property of potassium-loaded sodalite, which shows antiferromagnetic transition around 70 K, is reported. Monotonic narrow spectrum above 70 K is broadened below 70 K. The broadened spectrum is analyzed with an assumption that the broadening is given by dipolar field from magnetic moment in the cage of sodalite. Two Gaussian functions are...

Mikroporöse Magnete: Die Struktur der Titelverbindung (siehe Einschub) weist zweidimensionale Nickel‐Sauerstoff/Chlorid‐18‐Ring‐Schichten auf, die entlang der c‐Achse gestapelt und durch HPO3‐Einheiten verknüpft sind. Nach Messungen der magnetischen Anisotropie an ausgerichteten Einkristallen (siehe Graph) ist die leichte magnetische Achse senkrech...

Microporous magnets: The structure (inset) of the title compound features two‐dimensional nickel–oxygen/chloride 18‐ring layers, which are stacked along the c axis and pillared by HPO3 units. Magnetic anisotropy measurements (see picture) on aligned single crystals indicate that the magnetic easy axis is perpendicular to the layer plane.

Sodium clusters arrayed in aluminosilicate sodalite are known to show antiferromagnetism below the Néel temperature TN of 48 K. We have performed electron spin resonance (ESR) measurements on a powder specimen of this material at an X-band microwave frequency (9.7 GHz) with temperature varying between 4 and 300 K. The ESR spectra show asymmetric br...

Potassium clusters arrayed in zeolite A are known to show ferromagnetic properties at low temperatures. A remarkable decrease in the initial asymmetry was observed previously below the Curie temperature in zero-field μSR by using pulsed muons. In the present work by using dc muons, we clearly observed the fast decay component which was assigned to...

The zero-field muon spin relaxation in hydrogen tungsten bronze H(x)WO(3) was observed at temperatures between 5 K and 440 K in order to study the diffusion property of muons. The result shows that the relaxation curves are nearly identical at temperatures lower than 100 K and at above 100 K the relaxation rate becomes slower with increasing temper...

We performed μSR experiments on rubidium clusters arrayed in porous crystals of zeolite A. These clusters are known to show spontaneous magnetization of ferromagnetism at higher loading densities of Rb atoms in a previous study. The development of the internal field is observed below ≃4K in the temperature dependence of zero-field μSR spectra in th...