The optical constants n and k of thin manganese films of different thi
cknesses ranging from 20 up to 50 nm were determined in the spectral r
ange 3.5-20 mu m. The results were compared with the predictions of th
e Drude free electron theory and anomalous skin effect theory. The pre
vious theories were used to evaluate some micro characteristics of Mn
thin films such as the free charge concentration N, the relaxation tim
e tau, the static conductivity sigma(s), and the electron velocity at
Fermi surface V-F and the value of the effective area of Fermi surface
A(F). Using the optical constants, the optical conductivity (sigma =
sigma(1) + i sigma(2)) was also estimated. It was found that the contr
ibution of the effective absorption A(eff) equals 69%, i.e. the absorp
tion due to bound electrons may be 31%.