Determination of exchange constants of 2-D magnets from ESR in the paramagnetic state

Values of the exchange constant, J, of 2-dimensional magnets are obtained semi-quantitatively from measurements of the anisotropy of ESR line widths in the paramagnetic phase. The theory was reformulated to facilitate comparison with experiment. For cases in which J is known from the susceptibility, the agreement with our ESR derived values is within 30%. For the monolayer magnet, manganese stearate, a value of J/k = 0.5 K is found. Comparison of J to ordering (Neel) temperatures is made.