The existence of a quantum spin liquid (QSL) in which quantum fluctuations of spins are sufficiently strong to preclude spin ordering down to zero temperature was originally proposed theoretically more than 40 years ago, but its experimental realization turned out to be very elusive. Here we report on an almost ideal spin liquid state that appears to be realized by atomic-cluster spins on the triangular lattice of a charge-density wave state of 1T-TaS2. In this system, the charge excitations have a well-defined gap of ~0.3?eV, while nuclear quadrupole resonance and muon-spin-relaxation experiments reveal that the spins show gapless QSL dynamics and no long-range magnetic order at least down to 70 mK. Canonical T2 power-law temperature dependence of the spin relaxation dynamics characteristic of a QSL is observed from 200?K to Tf = 55?K. Below this temperature, we observe a new gapless state with reduced density of spin excitations and high degree of local disorder signifying new quantum spin order emerging from the QSL.
COBISS.SI-ID: 30689319
We upgraded conventional NQR spectrometer with opticallly pumped magetometer based on potasium vapours. We tested both measurement systems on detection of forbidden substances (exsplosives, narcotics and counterfeit drugs), which are diffucult to dectect with convetional system due to low RF signals. We observed up to ten times improvement of signal to noise ratio with the upgraded sprectrometer.
COBISS.SI-ID: 11677268
Naturally occurring tryptamines and their synthetic analogous present an important group of pharmaceutical products and dietary supplements. One of them is melatonin, a hormone found naturally in the body, which is responsible for regulation of sleep-wake cycles. In this study, it has been spectroscopically analyzed in the terahertz (THz) frequency region between 1.5 THz and 4.5 THz for the first time. Experimental results show a characteristic spectral feature of melatonin at 3.20 THz and one smaller absorption line at 4.20 THz, which allow its qualitative and quantitative analysis within the final products. In addition, THz spectroscopic imaging has been successfully applied for analysis of different concentrations of Circadin and melatonin as an active pharmaceutical ingredient (API) in the prepared pellets. Finally, we demonstrated that THz spectroscopy and imaging can be used as a complementary method to other analytical optical methods such as Fourier transform infrared spectroscopy when executing the quality control and verifying the authentications of dietary supplements such as melatonin.
COBISS.SI-ID: 31962407
A novel nonanuclear copper(II) nanocluster (Cu9) was constructed from a well-designed multidentate pyrazole-alcohol ligand and using various small anions. The Cu9 skeleton was found to consist of two similar Cu5 cluster units sharing one central CuII ion and to be protected by the outer organic ligand and auxiliary small anions. The solution behavior of Cu9 was studied in detail by applying the ESI-MS technique. Magnetism analysis implied the presence of antiferromagnetic interactions between the CuII ions.
COBISS.SI-ID: 18481241
In ACrF5 (A = Cs, Rb, K), Cr(IV) ions are coordinated by six fluoride ligands where the resulting CrF6 octahedra share cis vertexes to form infinite chains of ([Cr^{IV}F5]-)n. The geometry of the latter in Cs compound differs from that in K and Rb compounds. The results of investigations of the magnetic behaviour of these compounds have shown that an antiferromagnetic superexchange interaction is present within the chains with J(Cs) = -10.2 cm-1, J(Rb) = -13.3 cm-1, and J(K) = -13.1 cm-1
COBISS.SI-ID: 30403111