1,044 research outputs found
Деградация человеческого потенциала как фактор латентной составляющей деятельности высшей школы Украины
Рассмотрены проблемы тенизации и коррупционности функционирования украин-ской высшей школы на фоне вектора развития показателей потенциала населения страны.Розглянуті проблеми тінізації і коррупційності функціонування української вищої школи на тлі вектору розвитку показників потенціалу населення країни
Revealing the Formation of Copper Nanoparticles from a Homogeneous Solid Precursor by Electron Microscopy
Magnetic Properties of a Quantum Ferrimagnet: NiCu(pba)(D_2O)_3 . 2D_2O
We report the results of magnetic measurements on a powder sample of
NiCu(pba)(D_2O)_3 \cdot 2D_2OS\chi\chi TT\chi TJ/k_B=121
K^{2+}^{2+}g_{Ni}g_{Cu}\chi T$ at low temperatures
is reproduced fairly well by the calculation for the same ferrimagnetic model.Comment: 7pages, 4 postscript figures, usues REVTEX. appear in J. Phys. Soc.
Jpn vol 67 No.7 (1998
Magnetic properties of the spin-1 chain compound NiClCHCHCHNH
We report experimental results of the static magnetization, ESR and NMR
spectroscopic measurements of the Ni-hybrid compound
NiClCHCHCHNH. In this material NiCl octahedra are
structurally arranged in chains along the crystallographic -axis. According
to the static susceptibility and ESR data Ni spins are isotropic
and are coupled antiferromagnetically (AFM) along the chain with the exchange
constant K. These are important prerequisites for the realization of
the so-called Haldane spin-1 chain with the spin-singlet ground state and a
quantum spin gap. However, experimental results evidence AFM order at K presumably due to small interchain couplings. Interestingly,
frequency-, magnetic field-, and temperature-dependent ESR measurements, as
well as the NMR data, reveal signatures which could presumably indicate an
inhomogeneous ground state of co-existent mesoscopically spatially separated
AFM ordered and spin-singlet state regions similar to the situation observed
before in some spin-diluted Haldane magnets
Electronic density of states derived from thermodynamic critical field curves for underdoped La-Sr-Cu-O
Thermodynamic critical field curves have been measured for
over the full range of carrier concentrations
where superconductivity occurs in order to determine changes in the normal
state density of states with carrier concentration. There is a substantial
window in the plane where the measurements are possible because the
samples are both thermodynamically reversible and the temperature is low enough
that vortex fluctuations are not important. In this window, the data fit
Hao-Clem rather well, so this model is used to determine and
for each temperature and carrier concentration. Using N(0) and the ratio of the
energy gap to transition temperature, , as fitting
parameters, the curves give over the
whole range of . Values of N(0) remain rather constant in the optimum-doped
and overdoped regime, but drops quickly toward zero in the underdoped regime.
Ga NMR study of the local susceptibility in SrCr8Ga4O19: pseudogap and paramagnetic defects
We present the first Ga(4f) NMR study of the Cr susceptibility in the
archetype of Kagome based frustrated antiferromagnets,
SrCrGaO. Our major finding is that the susceptibility of the
frustrated lattice goes through a maximum around 50 K. Our data also supports
the existence of paramagnetic ``clusters'' of spins, responsible for the Curie
behavior observed in the macroscopic susceptibility at low T. These results set
novel features for the constantly debated physics of geometrically frustrated
magnets.Comment: 4 pages, 5 figures Submitted to Phys. Rev. Let
New quantum phase transitions in the two-dimensional J1-J2 model
We analyze the phase diagram of the frustrated Heisenberg antiferromagnet,
the J1-J2 model, in two dimensions. Two quantum phase transitions in the model
are already known: the second order transition from the Neel state to the spin
liquid state at (J_2/J_1)_{c2}=0.38, and the first order transition from the
spin liquid state to the collinear state at (J_2/J_1)_{c4}=0.60. We have found
evidence for two new second order phase transitions: the transition from the
spin columnar dimerized state to the state with plaquette type modulation at
(J_2/J_1)_{c3}=0.50(2), and the transition from the simple Neel state to the
Neel state with spin columnar dimerization at (J_2/J_1)_{c1}=0.34(4). We also
present an independent calculation of (J_2/J_1)_{c2}=0.38 using a new approach.Comment: 3 pages, 5 figures; added referenc
- …