Ferromagnetic resonance in multilayer [Fe/Cr]n structures with noncollinear magnetic ordering

The excitation spectrum in an [Fe/Cr]n multilayer structure with non-collinear magnetic ordering was studied by the ferromagnetic resonance (FMR) method in the frequency interval 9.5–37 GHz at room temperature. Besides an acoustic branch, several additional modes were observed under parallel excitation of resonance. The FMR spectrum was calculated analytically in a biquadratic exchange model, neglecting in-plane anisotropy, for an infinite number of layers in the structure and numerically for a finite number of layers contained in real samples. It was shown that the observed modes correspond to excitation of standing spin waves with wave vectors perpendicular to the film plane. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 690–695 (10 May 1998)     

Trifluoromethyl Sulfones and Perfluoroalkanesulfonamides of the Azole Series

2-Phenyl-4-trifluoromethylsulfonylmethyl-2H-1,2,3-triazole was synthesized from 4-bromo-methyl-2-phenyl-2H-1,2,3-triazole and sodium trifluoromethanesulfinate CF₃SO₂Na. 1(2)-Ethyl-4-nitro-1(2)H-1,2,3-triazoles and 4-nitro-2-phenyl-2H-1,2,3-triazole were reduced to the corresponding amines. Intermediate 1,2-bis(1-ethyl-1H-1,2,3-triazol-4-yl)diazene 1-oxide exists as a mixture of syn and anti isomers, the former being stabilized via formation of a strong intramolecular hydrogen bond. The reduction of 2-ethyl-4-nitro-2H-1,2,3-triazole in the presence of HCl afforded the target 4-amino-2-ethyl-2H-1,2,3-triazole and also 4-amino-5-chloro-2-ethyl-2H-1,2,3-triazole. Treatment of alkyl-substituted 4-amino-1,2,3-triazoles with trifluoromethanesulfonyl chloride and pentafluoroethanesulfonyl chloride gave N-triazolyl-substituted trifluoromethane- and pentafluoroethanesulfonamides and -imides.     

Azoles and Azines: CXIX. Alkylation of 5,5'-(4-Nitrobenzylidene)bis(2-thiobarbituric) Acid and 5-(4-Nitrophenyl)-2,8-dithioxo-5,7,8,9-tetrahydro-2H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(1H,3H)-dione with Haloacetic Acids and Their Esters

5,5'-(4-Nitrobenzylidene)bis(2-thiobarbituric) acid and 5-(4-nitrophenyl)-2,8-dithioxo-5,7,8,9-tetrahydro-2H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(1H,3H)-dione, similar to unsubstituted 2-thiobarbituric acid, readily react with haloacetic acids and their esters to form regioselectively the S-alkylation products. The alternative routes fo 5,5'-(4-nitrobenzylidene)bis[(4-hydroxy-6-oxo-1,6-dihydropyrimidine-5,2-diyl)sulfanyl]diacetic acids, based on condensation of 4,6-dihydroxypyrimidin-2-ylthioacetic acid with carbonyl compounds followed by cyclodehydration to [(5-(4-nitrophenyl)-4,6-dioxo-3,5,6,7-tetrahydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-2,8-diyl)di(sulfanyl)]diacetic acid derivatives, are less efficient. Alkylation of 2-thiobarbituric acid with ethyl bromoacetate in ethanol in the presence of alkali yields 5-(2-oxo-2,5-dihydro-1,3-thiazol-4-yl)-2-thiobarbituric acid.     

Crystal field and magnetization of canted antiferromagnet CoCO<Subscript>3</Subscript>

The magnetization of the canted antiferromagnet CoCO₃ (T _N = 18.1 K) is calculated in the Weiss molecular field approximation taking into account the microscopic state of the Co²⁺ ion in the entire range of temperatures and magnetic fields. The values of T _N, magnetic susceptibility in the basal plane, and ferromagnetic moment were used as parameters. It is shown that the anisotropy of the g factor and of the exchange interaction at low temperatures (T < 30 K) including the magnetic ordering temperature is correctly described in the Abragam-Pryce approximation. At high temperatures, the g factor increases and becomes isotropic, but it cannot be described using the Abragam-Pryce approximation. The reasons for g factor variation and the magnitude of the magnetic moment are discussed.     

Influence of velocity nonuniformity in a medium on the penetration of cumulative jets and extended flyer plates

Obstacle materials into which plane cumulative jets with an initial impact velocity of 2.5–3.5 km/s penetrate are studied metallographically. The results suggest that penetration takes place in the nonuniform velocity field of the medium. A refined hydrodynamic model for the fast penetration of jets and flyer plates is put forward and verified experimentally.