649 research outputs found
Magnetic properties of CuxMn1 x 3[Cr CN 6]2.zH2O complexes
Magnetization measurements were performed on the CuxMn1 x 3[Cr CN 6]2.zH2O molecule based magnets where x 0 0, 0.2, 0.25, 0.3, 0.35 0.4, 0.6, 0.8 and 1.0. Both the Curie temperature and saturated magnetization at first decrease with increasing value of x reaching the minimal value of TC 49 7 K and 0 17 B for x 0 2 and then increase with substitution. The pronounced hysteretic behavior between zero field cooled and field cooled regimes was observed for all samples. Magnetization changes the sign of magnetic polarization in zero field cooled magnetization curve at the compensation temperature Tcomp 16 K for sample with x 0 4. Our results indicate that the system behaves as mixed ferri ferromagnetic syste
Strong accessibility of Coxeter groups over minimal splittings
AbstractGiven a class of groups C, a group G is strongly accessible over C if there is a bound on the number of terms in a sequence Λ1,Λ2,…,Λn of graph of groups decompositions of G with edge groups in C such that Λ1 is the trivial decomposition (with 1-vertex) and for i>1, Λi is obtained from Λi−1 by non-trivially and compatibly splitting a vertex group of Λi−1 over a group in C, replacing this vertex group by the splitting and then reducing. If H and K are subgroups of a group G then H is smaller than K if H∩K has finite index in H and infinite index in K. The minimal splitting subgroups of G, are the subgroups H of G, such that G splits non-trivially (as an amalgamated product or HNN-extension) over H and for any other splitting subgroup K of W, K is not smaller than H. When G is a finitely generated Coxeter group, minimal splitting subgroups are always finitely generated. Minimal splittings are explicitly or implicitly important aspects of Dunwoody’s work on accessibility and the JSJ results of Rips–Sela, Dunwoody–Sageev and Mihalik. Our main results are that Coxeter groups are strongly accessible over minimal splittings and if Λ is an irreducible graph of groups decomposition of a Coxeter group with minimal splitting edge groups, then the vertex and edge groups of Λ are Coxeter
Synthesis, structural and magnetic properties of TM22+[MOIV(CN)(8)]center dot nH(2)O
Octacyanomolybdates (OCMs) TM2 divided by[Mo(CN)(8)]center dot nHO, where TM is Mn, Fe, Co, Ni, Cu were synthesised and characterised by IR spectroscopy and UV-VIS spectroscopy. The UV-VIS spectrum showed the intervalence charge transfer (IVCT) band between Mo-IV-CN-Cu-II and Mo-V-CN-Cu-I around 510 nm. Studied OCMs adopt tetragonal crystal structure. The H-1 NMR signals reflect the magnetic moment of the TM2- ions (mu(P)). The decay rates of free induction decay (FID) signals
increase as pp and the applied static rf-field increases. The
spin-lattice relaxation times at 27.7 MHz vary from 0.0187 ins (Mn) up to 0.45 ms (Cu). Magnetization measurements indicate long-range magnetic ordering of Mn- and Co- OCMs with the Curie temperature T-c = 4 K. The remaining OCMs (TM is Fe, Ni, Cu) are paramagnetic down to T = 1.9 K
Superconductivity in the YIr2Si2 and LaIr2Si2 Polymorphs
We report on existence of superconductivity in YIr2Si2 and LaIr2Si2 compounds
in relation to crystal structure. The two compounds crystallize in two
structural polymorphs, both tetragonal. The high temperature polymorph (HTP)
adopts the CaBe2Ge2-structure type (space group P4/nmm) while the low
temperature polymorph (LTP) is of the ThCr2Si2 type (I4/mmm). By studying
polycrystals prepared by arc melting we have observed that the rapidly cooled
samples retain the HTP even at room temperature (RT) and below. Annealing such
samples at 900C followed by slow cooling to RT provides the LTP. Both, the HTP
and LTP were subsequently studied with respect to magnetism and
superconductivity by electrical resistivity, magnetization, AC susceptibility
and specific heat measurements. The HTP and LTP of both compounds respectively,
behave as Pauli paramagnets. Superconductivity has been found exclusively in
the HTP of both compounds below Tsc (= 2.52 K in YIr2Si2 and 1.24 K in
LaIr2Si2). The relations of magnetism and superconductivity with the electronic
and crystal structure are discussed with comparing experimental data with the
results of first principles electronic structure calculations
Valence band and core levels of Ce5Ni2Si3 crystal studied by X-ray photoemission spectroscopy
The crystal of Ce5Ni2Si3 was prepared by the Czochralski method. The X-ray photoemission spectroscopy was measured for the valence band and the core levels. Based on the Ce(3d) doublet and its satellites a small value
of the hybridization parameter of the f-states with the conduction electrons ¢ = 4 meV and the f-occupancy nf close to 1 were found. X-ray photoemission spectroscopy shows that the region between 0 and 3 eV is predominated by the Ni(3d) and Ce(4f) peaks. Some features of the multiplet structure of
the Ce(4f) states are also visible close to the Fermi level
Magnetic and Transport Properties of PrNi Single Crystal
Frequency dependence of χ (T ), different position of a maximum in χ (T ) for different crystal orientations, hysteretic behavior between magnetization measurements in zero-field cooling and field coolding regime are attributed to strong magneto-crystalline anisotropy of PrNi ferromagnetic single crystal with T C = 20.5 K, which is driven by crystal field effect. Applied pressure shifts T C to higher temperatures (dT C /dp = 1 K/GPa). Susceptibility follows the Curie-Weiss law except for b-axis, which is hard magnetic axis. An anisotropic behavior was seen in resistivity measurements with the largest difference between b-axis and c-axis. Resistivity below TC can be described by power law with ρ ∼ T 2.24 and is field dependent with a positive magnetoresistance
Safe-Play Knowledge, Aggression, and Head-Impact Biomechanics in Adolescent Ice Hockey Players
Addressing safe-play knowledge and player aggression could potentially improve ice hockey sport safety
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