Weak exchange degeneracy in the reactionsπ+p→K+Σ+andK−p→π−Σ+at 4, 7, 11.5, and 70 GeV/c

A simple hexagonal array of classical spins coupled by nearest-neighbour antiferromagnetic Heisenberg interactions has a ground state with a triangular antiferromagnetic configuration of spins. We have developed spin wave theory for triangular antiferromagnets with both Heisenberg and dipole–dipole interactions. The dipole–dipole interactions confine the spins to the hexagonal basal plane and they do not distort the equiangular triangular structure. Spin wave dispersion relations are plotted for some trial values of the exchange constants. The theory is applied to the triangular antiferromagnet CsMnBr3. This is a quasi-one-dimensional material with strong exchange interactions along the hexagonal axes and with weak exchange interactions within the basal plane that are of the same order as dipolar interactions.

Download Full-text

An electron spin resonance study of certain vanadyl polyaminocarboxylate chelates formed in aqueous and frozen aqueous solutions

Australian Journal of Chemistry ◽

10.1071/ch9742535 ◽

1974 ◽

Vol 27 (12) ◽

pp. 2535 ◽

Cited By ~ 15

Author(s):

TD Smith ◽

JF Boas ◽

JR Pilbrow

Keyword(s):

Electron Spin Resonance ◽

Electron Spin ◽

Exchange Coupling ◽

Electron Spin Resonance Study ◽

Ph Titration ◽

Weak Exchange ◽

Spin Resonance ◽

Dimeric Form ◽

Firm Evidence ◽

Spin Resonance Study

Potentiometric pH-titration and electron spin resonance studies have shown the existence of mono-meric, dimeric and dinuclear vanadyl chelates of certain polyaminocarboxylic acids. The ligands studied include ethylenediaminetetraacetic (edta), ethyleneglycolbis(β- aminoethyl ether)-N,N?-tetra-acetic (egta), diethylenetriaminepentaacetic (dtpa) and triethylenetetraaminehexaace- tic (ttha) acids. All the ligands form 1 : 1 chelates. The addition of ethylene glycol to the aqueous solution in each case provides circumstances for the study of the monomeric chelates, though it is not equally effective in all cases. The 1 : 1 vanadyl egta chelate above pH 5.5 gave rise to ΔMS = � 2 and ΔMS = � 1 transitions from which structural and magnetic parameters have been determined and interpreted in terms of the formation of a dimeric form of a hydrolytic product of the 1 : 1 chelate. Firm evidence for the formation of dinuclear chelates occurs only in the vanadyl ttha system. Here the room tem- perature e.s.r. spectrum shows the presence of weak exchange coupling between the vanadyl ions in the dinuclear chelate.

Download Full-text