It has recently been suggested that the organic compound NiCl2-4SC(NH2)2 (DTN) undergoes field-induced Bose-Einstein condensation (BEC) of Ni spin degrees freedom. The S = 1 spins exhibit three-dimensional XY antiferromagnetism above a critical field H(c1) approximately 2 T. fluid can be described as gas hard-core bosons where antiferromagnetic transition corresponds to condensation. We have determined Hamiltonian DTN using inelastic neutron diffraction measurements, and we studied...

NiCl$_2$-4SC(NH$_2$)$_2$ (DTN) is a quantum S=1 chain system with strong easy-pane anisotropy and new candidate for the Bose-Einstein condensation of spin degrees freedom. ESR studies magnetic excitations in DTN fields up to 25 T are presented. Based on analysis single-magnon excitation mode high-field spin-polarized phase previous experimental results [Phys. Rev. Lett. 96, 077204 (2006)], revised set spin-Hamiltonian parameters obtained. Our yield $D=8.9$ K, $J_c=2.2$ $J_{a,b}=0.18$ K...

Several quantum paramagnets exhibit magnetic-field-induced phase transitions to an antiferromagnetic state that exists for H c1 ≤ c2. For some of these compounds, there is a significant asymmetry between the low- and high-field transitions. We present specific heat thermal conductivity measurements in NiCl2-4SC(NH2)2, together with calculations which show caused by strong mass renormalization due fluctuations are absent ≥ argue enigmatic lack concomitant impurity scattering.

We have investigated the low-temperature T field-induced ordering in ${\mathrm{NiCl}}_{2}\ensuremath{\cdot}4\mathrm{SC}({\mathrm{NH}}_{2}{)}_{2},$ from magnetization measurements. This is an $S=1$ system with a large single-ion uniaxial anisotropy leaving singlet ground state. An external magnetic field $(\mathbf{B})$ parallel to symmetry axis induces antiferromagnetically ordered phase for ${B}_{c1}<B<{B}_{c2}.$ The establishment of this long-range order can be regarded as Bose-Einstein...

In this work, we demonstrate field-induced Bose-Einstein condensation (BEC) in the organic compound ${\mathrm{NiCl}}_{2}\mathrm{\text{\ensuremath{-}}}4\mathrm{SC}({\mathrm{NH}}_{2}{)}_{2}$ using ac susceptibility measurements down to 1 mK. The Ni $S=1$ spins exhibit 3D $XY$ antiferromagnetism between a lower critical field ${H}_{c1}\ensuremath{\sim}2\text{ }\text{ }\mathrm{T}$ and upper ${H}_{c2}\ensuremath{\sim}12\text{ }\mathrm{T}$. results show power-law temperature dependence of phase...

By means of nuclear spin-lattice relaxation rate ${T}_{1}^{\ensuremath{-}1}$, we follow the spin dynamics as a function applied magnetic field in two gapped quasi-one-dimensional quantum antiferromagnets: anisotropic spin-chain system ${\mathrm{NiCl}}_{2}\mathrm{\text{\ensuremath{-}}}4\mathrm{SC}({\mathrm{NH}}_{2}{)}_{2}$ and spin-ladder $({\mathrm{C}}_{5}{\mathrm{H}}_{12}\mathrm{N}{)}_{2}\mathrm{Cu}{\mathrm{Br}}_{4}$. In both systems, excitations are confirmed to evolve from magnons state...

We present a comprehensive experimental and theoretical investigation of the thermodynamic properties: specific heat, magnetization, thermal expansion in vicinity field-induced quantum critical point (QCP) around lower field ${H}_{c1}\ensuremath{\approx}2$ T NiCl${}_{2}$-4SC(NH${}_{2}$)${}_{2}$. A ${T}^{3/2}$ behavior heat magnetization is observed at very low temperatures $H={H}_{c1}$, which consistent with universality class Bose-Einstein condensation magnons. The temperature dependence...

5-(3-(N-tert-Butyl-N-aminoxyl)phenyl)pyrimidine (RL = 3NITPhPyrim) forms isostructural cyclic M2(RL)2 dimers with M(hfac)2 (M Mn, Co, Cu; hfac hexafluoroacetylacetonate). Mn2(hfac)4(RL)2 exhibits strong antiferromagnetic Mn-RL exchange, weak ferromagnetic exchange (0.7 cm(-1)) between units that is consistent a spin polarization mechanism. The magnetic moment of Co2(hfac)4(RL)2 at higher temperatures strongly within the Co-NIT and tends toward zero below 50 K lower fields. Cu2(hfac)4(RL)2...

The magnetic phase diagram of the antiferromagnetic Ni${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}6${\mathrm{H}}_{2}$O (${T}_{N}=5.34$ K) was determined from $\frac{\mathrm{dM}}{\mathrm{dH}}$ measurements down to temperatures $T$ as low 0.35 K, and in fields $H$ up 150 kG. $T=0$ spin-flop field canted-paramagnetic critical were ${H}_{\mathrm{SF}}(0)=39.45\ifmmode\pm\else\textpm\fi{}0.30$ kG ${H}_{c}(0)=143.9\ifmmode\pm\else\textpm\fi{}1.5$ kG, respectively. From these...

Strongly correlated spin systems can be driven to quantum critical points via various routes. In particular, gapped antiferromagnets undergo phase transitions into a magnetically ordered state with applied pressure or magnetic field, acting as tuning parameters. These are characterized by z = 1 2 dynamical exponents, determined the linear and quadratic low-energy dispersion of excitations, respectively. Employing high-frequency susceptibility ultrasound techniques, we demonstrate that...

We demonstrate that the short-range spin correlator $⟨{\mathbf{S}}_{i}\ensuremath{\cdot}{\mathbf{S}}_{j}⟩$, a fundamental measure of interaction between adjacent spins, can be directly measured in certain insulating magnets. present magnetostriction data for organic compound $\mathrm{Ni}{\mathrm{Cl}}_{2}\text{\ensuremath{-}}4\mathrm{S}\mathrm{C}{(\mathrm{N}{\mathrm{H}}_{2})}_{2}$, and show as function field is proportional to dominant correlator. Furthermore, constant proportionality gives...

The boundaries between the paramagnetic, antiferromagnetic, and spin-flop phases of ${\mathrm{K}}_{2}$[Fe${\mathrm{Cl}}_{5}$(${\mathrm{H}}_{2}$O)] have been determined by means ac susceptibility measurements in an applied magnetic field. With ${T}_{c}(0)=14.06$ K, we find bicritical point at 13.6 K 34.1 kOe, ${H}_{\mathrm{SF}}(0)=26$ derive ${H}_{A}=1.7$ ${H}_{E}=199$ kOe. Similarly, for ${\mathrm{Rb}}_{2}$[Fe${\mathrm{Cl}}_{5}$(${\mathrm{H}}_{2}$O)], ${T}_{c}(0)=10.03$ ${T}_{b}=10$ 18...

Metal-organic materials constitute a new field in which to search for ferroelectricity and coupling between electricity magnetism. We observe magnetic field-induced change the electric polarization, $\ensuremath{\Delta}\mathbf{P}(H)$, that reaches 50 $\ensuremath{\mu}$C/m${}^{2}$ single crystals of NiCl${}_{2}$--4SC(NH${}_{2}$)${}_{2}$ (DTN). DTN forms tetragonal structure breaks inversion symmetry with electrically polar thiourea molecules [SC(NH${}_{2}$)] all tilted same direction along...

We report results of magnetoacoustic studies in the quantum spin-chain magnet ${\text{NiCl}}_{2}\text{\ensuremath{-}}4\text{SC}{({\text{NH}}_{2})}_{2}$ (DTN) having a field-induced ordered antiferromagnetic (AF) phase. In vicinity critical points (QCPs) acoustic ${c}_{33}$ mode manifests pronounced softening accompanied by energy dissipation sound wave. The anomalies are traced up to $T>{T}_{N}$, where thermodynamic properties determined fermionic magnetic excitations, ``hallmark''...

The zero-field susceptibilities parallel and perpendicular to the tetragonal axis of NiCl2⋅4SC(NH2)2 have been measured between 1.2 30 K fitted usual spin Hamiltonian. resulting parameters are D/kB = 7.6±0.4 K, z0J/kB −4.5±0.3 g∥ 2.26±0.03 g⊥ 2.34±0.03. susceptibility has also at constant temperatures 0.3 2 as a function external field. Magnetic ordering is found occur, portions phase boundary paramagnetic antiferromagnetic states determined.

$\mathrm{Ni}{\mathrm{Cl}}_{2}\text{\ensuremath{-}}4\mathrm{S}\mathrm{C}{(\mathrm{N}{\mathrm{H}}_{2})}_{2}$ (known as DTN) is a spin-1 material with strong single-ion anisotropy that regarded new candidate for Bose--Einstein condensation (BEC) of spin degrees freedom. We present systematic study the low-energy excitation spectrum DTN in field-induced magnetically ordered phase by means high-field electron resonance measurements at temperatures down to...

The title radical (F4BImNN) is a stable nitronylnitroxide that forms hydrogen-bonded NH... ON chains in the solid state. assemble F4BImNN molecules to form stacked contacts between groups, geometry expected exhibit ferromagnetic (FM) exchange based on spin polarization (SP) models. experimental magnetic susceptibility of confirms expectation, showing 1-D Heisenberg chain FM behavior over 1.8-300 K with an intrachain constant Jchain/k = +22 K. At lower temperatures, ac and variable field heat...

In this paper we investigate the quantum phase transition from magnetic Bose Glass to Bose-Einstein condensation induced by a field in NiCl${}_{2}\ifmmode\cdot\else\textperiodcentered\fi{}$4SC(NH${}_{2}$)${}_{2}$ (dichloro-tetrakis-thiourea-nickel, or DTN), doped with Br (Br-DTN) site diluted. Quantum Monte Carlo simulations for of model Hamiltonian Br-DTN, as well site-diluted DTN, are consistent conventional scaling at critical point and exponent $z$ verifying prediction $z=d$; moreover...

Mixtures of 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (F4BImNN) and 2-(benzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (BImNN) crystallize as solid solutions (alloys) across a wide range binary compositions. (F4BImNN)(x)(BImNN)((1-x)) with x < 0.8 gives orthorhombic unit cells, while ≥ 0.9 monoclinic cells. In all crystalline samples, the dominant intermolecular packing is controlled by one-dimensional...

Field-induced magnetic ordering in the structurally disordered quantum magnets Ni(Cl${}_{1\ensuremath{-}x}$Br${}_{x}$)${}_{2}$$\phantom{\rule{0.16em}{0ex}}\ifmmode\cdot\else\textperiodcentered\fi{}\phantom{\rule{0.16em}{0ex}}$4SC(NH${}_{2}$)${}_{2}$, $x=8$% and 13%, is studied by means of neutron diffraction. The order-parameter critical exponent found to be very close its value $\ensuremath{\beta}=0.5$ expected for Bose-Einstein condensation absence disorder. This result applies...

Mn(hfac)(2) and Cu(hfac)(2) form coordination complexes with 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine, PyrimPh-NIT. (Mn[PyrimPh-NIT](hfac)(2))(2) (Cu[PyrimPh-NIT](hfac)(2))(2), 1 2, respectively, are cyclic M(2)L(2) dimers that exhibit strong exchange coupling between the coordinated paramagnetic dication (M) nitroxide (NIT) unit. The M-NIT is strongly antiferromagnetic (AFM) in ferromagnetic (FM) 2. Magnetic susceptibility measurements for were fitted to an AFM spin pairing model J/k...

One pair of reactants, Cu(hfac)(2) = M and the hinge-flexible radical ligand 5-(3-N-tert-butyl-N-aminoxylphenyl)pyrimidine (3PPN L), yields a diverse set five coordination complexes: cyclic loop M(2)L(2) dimer; 1:1 cocrystal between an ML(2) fragment; 1D chain loops linked by M; two 2D M(3)L(2) networks (M-L)(n) chains cross-linked with different repeat length pitches; 3D network cross-linking (M-L)(n)-type connectivity from those in networks. Most higher dimensional complexes exhibit...

The NiCl${}_{2}$-4SC(NH${}_{2}$)${}_{2}$ spin-chain compound, also called ``DTN'', is one of the most studied archetype materials that at low temperature presents magnetic-field-induced ordered phase described as a Bose-Einstein condensate (BEC). paper here an NMR study static properties this phase, where, for first time, exact absolute value order parameter has been determined and compared to theoretical predictions. precise boundary BEC close its upper critical field found be in perfect...