DETERMINATION OF THE ANTIFERROMAGNETIC EXCHANGE CONSTANT BETWEEN NEAREST-NEIGHBOR Mn** plus ** plus IONS IN Cd//0//. //9//5 Mn//0//. //0//5 Se.

Abstract

The optical splitting of the A-exciton in Cd//0//. //9//5 Mn//0//. //0//5 Se has been measured at 1. 45 K with dc magnetic fields B up to 20 T applied along the c-axis. Magnetization measurements have been made at 1. 8 K with pulsed magnetic fields up to 28 T. The A-exciton splitting vs. B curve as well as the magnetization vs. B curve show a temperature-broadened step-like increase at B//1 equals 13. 0 plus or minus 0. 5 T which is attributed to the magnetic field induced alignment of the antiferromagnetically coupled nearest-neighbor Mn** plus ** plus ion pairs, and yields a value J equals minus 8. 7 plus or minus 0. 3 K for the antiferromagnetic exchange constant. The magnetization curve shows a second step at B//2 congruent 25 T; three additional steps are expected before a complete ferromagnetic alignment of the pairs is achieved at B congruent 65 T.