EPR STUDY OF QUASI-CRYSTALLINE Al//8//6Mn//1//4 ALLOY.

Abstract

Quasi-crystalline Al//8//6Mn//1//4 alloy gives no electron paramagnetic resonance (EPR) signal at 300 K (or down to 130 K), whereas the same alloy after transformation by heat treatment (3 hrs at 900 degree K) gives a resonance signal at 2. 15 kOe ( DELTA H equals 0. 97 kOe) at room temperature. The spherical harmonics of 1 equals 2 which correspond to d-wave functions are completely degenerate in an icosahedral crystal field and the lifting of degeneracy on transformation to orthorhombic Al//6 Mn is argued to be the reason for the appearance of an EPR signal after transformation. Magnetic susceptibility measurements on icosahedral Al//8//6Mn//1//4 alloy have also been carried out and the results are discussed in the light of the calculated electronic structure of the icosahedral Al-Mn clusters.