Ferrimagnetic resonance in films of vanadium [tetracyanoethanide]x, grown by chemical vapor deposition

Journal ArticleFerrimagnetic resonance (FMR) measurements in thin films of V[TCNE]x grown by chemical vapor deposition exhibit a series of sharp lines at 300 K. The orientational dependence of these lines is a result of the sample geometry provided the magnetization tracks the applied magnetic field. The FMR intensities scale with the temperature dependence of the magnetization as measured by SQUID magnetometry. The temperature dependence of the FMR at various orientations yields an estimate of the local, negative anisotropy field, which is approximately 200 Oe at zero temperature and decreases linearly with increasing temperature and is well fit by a model developed for spin glasses. The widths of the FMR lines track the temperature dependence of the magnetization, which suggests that they are determined by density fluctuations. The spacings between the individual FMR lines and their temperature dependence are consistent with the presence of nonlinear spin waves, whose critical microwave field is approximately 10-2 Oe. A rough estimate of the exchange stiffness constant is A=10-10 erg/cm. The small value of A may be due to the magnitude of the antiferromagnetic exchange between V and adjacent TCNE and the frustration of AFM exchange between adjacent TCNE radicals

MARKETING OF COTTON FIBER IN THE PRESENCE OF YIELD AND PRICE RISK

An expected utility model and a chance constrained linear programming model were used to analyze four marketing strategies and seven crop insurance alternatives in cotton marketing in Georgia. The results obtained suggest that the existing marketing tools and insurance alternatives can be used successfully as a substitute for government support.Demand and Price Analysis, Marketing, Risk and Uncertainty,

Characterization of novel TCNQ and TCNE 1 : 1 and 1 : 2 salts of the tetrakis(dimethyamino) ethylene dication, [{(CH3)2N}2C-C{N(CH3)2}2]2+

Journal ArticleAddition of TCNQ to a solution of tetrakis(dimethylamino)ethylene in MeCN produces the salt [TDAE][TCNQ]2; the dipositive cation, [{(CH3)2N}2C-C{N(CH3)2}2]2+, is nonplanar, with a dihedral angle of 63.9(o), while the TCNQ anions crystallize as [TCNQ]2 2- dimers with an interplanar separation of 3.16 A. The complex [TDAE][TCNE] was prepared in a similar manner; the [TDAE]2 + cation and [TCNE]2- anion are nonplanar, with dihedral angles of 71.3 and 76.6(o), respectively. The four CN groups in the [TCNE]2- anion each accept three C-H...N hydrogen bonds. In each case, one C-N...H angle is in the range 134-156(o), while the other two are near 90(o) (81-100(o)

Novel co-operative magnetic properties of decamethylmanganocenium 2,3-dichloro-5,6-dicyanobenzoquinoneide, 3[Mn(C5Me5)2]:+[DDQ].-

Journal ArticleThe electron-transfer salt 3[Mn(C5Me5)2]: + [DDQ].-, isomorphous to orthorhombic [Fe(C5Me5)2].+[DDQ].-, has been prepared. It exhibits a complex field-dependent magnetic phase diagram at low temperatures with evidence for ferromagnetic coupling as well as a low moment state below 4 K for zero-field cooled samples

Decamethylchromocenium tetracyanoethenide, + [Cr(C5Me5)2]:.+[TCNE].-: a molecular ferromagnet with Tc=3.65 K

Journal ArticleThe electron-transfer salt 4[Cr(C5Me5)2] + [TCNE].-(TCNE = tetracyanoethylene) has been prepared and structurally characterized by single-crystal X-ray diffraction. It possesses a solid-state motif of parallel 1D chains of alternating radical cations and anions similar to, but not isostructural to, the ferromagnet [Fe(C5Me5)2].+ [TCNE]. -.4[Cr(C5Me5)2] + [TCNE].- is a soft ferromagnet with no hysteretic effects observed and Tc = 3.65 K

Novel coordination of dicyanamide, [N(CN)2]-: preferential binding of the amide nitrogen

Journal ArticleCoII[N(CN)2]2(H2BiIm)2, 1, and {CoII[N(CN)2](H- 2BiIm)2}Cl, 2 (H2BiIm = 2,2'-biimidazole) have been structurally, spectroscopically, and magnetically characterized with both containing dicyanamides bound in unprecedented manners; namely, solely via the amide nitrogen for 1, and via an imide N forming 1-D helical chains for 2

Collinear ferromagnetism and spin orientation in the molecule-based magnets M[N(CN)2]2 (M=Co,Ni)

Journal ArticleZero-field unpolarized neutron powder diffraction has been used to study the low-T magnetic structure and T-dependent crystal structure of M[N(CN)2]2 (M=Co,Ni). Both compounds show collinear ferromagnetism with spin orientation along the c axis. The results provide the determination of a complete magnetic structure in the ordered state for a molecule-based magnet. The c lattice parameter exhibits negative thermal expansion, explained by a wine-rack-like deformation

Optical properties of the 1:2 compound of dimethylferrocenium with tetracyanoquinodimethanide: [(Me2Fc)(TCNQ)2]

Journal ArticleWe present the results of a study of the room-temperature polarized reflectance of (1:2) 1,1'-dimethylferrocenium ditetracyanoquinodimethanide [(Me2Fc)(TCNQ)2] over the range between the far infrared and the near ultraviolet. Kramers-Kronig analysis of the reflectance is used to determine the optical properties of the compound. Vibrational features are evident at low frequencies whereas electronic excitations, including charge transfer between TCNQ molecules, are observed at higher frequencies

Optical properties of quinolinium tetracyanoquinodimethanide, [Qn(TCNQ)2] and (N-methylphenazinium)x(phenazine)1-x (tetracyanoquinodimethane) [(NMP)x(Phen)1-x(TCNQ)]

Journal ArticleWe present here optical-absorption data of quinolinium ditetracyanoquinodimethanide [Qn(TCNQ)2] and (N-methylphenazinium)x(phenazine)1-x(tetracyanoquinodimethanide) [(NMP)x(Phen)1-x(TCNQ)] for 0.5 <_x<_ 0.6. These materials span the range of electronic structure from commensurate, to commensurate with confined soliton-antisoliton pairs (bipolarons), to incommensurate. The data show that these materials are semiconductors up to 300 K. The semiconducting gap, due mostly to a Peierls distortion, is weakly temperature dependent, decaying slowly as the temperature increases. This behavior, determined by the observation of the totally symmetric a, vibrational modes of the TCNQ molecule, is similar for all compositions studied and is suggested to be due to the effects of an external cation potential or to Coulomb effects, which vary little with composition. Substantial in-gap absorption is observed and is suggested to be due to the presence of quantum-nucleated and thermally generated bipolarons. The variation of higher-energy electronic transitions with composition corresponds to a crossover from commensurate to incommensurate electronic structure