Doped semiconductor as an amorphous antiferromagnet

Abstract

The antiferromagnetic exchange interaction between shallow donors in a semiconductor at a concentration below the metal-insulator transition makes this system a model "amorphous antiferromagnet." A recent pair model for the spin susceptibility of $n$-CdS [M. Rosso, Phys. Rev. Lett. 44, 1451 (1980)] is here extended to the case of Si: P. The results are compared with experimental values for the magnetic dependence of the spin susceptibility and the specific heat. Comparison is also made with "exact" cluster calculations. In the mK range it is found that hyperfine interactions are important. In particular, they give rise to pronounced features in the extrinsic specific heat at ∼2 mK. MS code no.