Study on the electronic structure of monocrystalline terbium - yttrium alloys by positron annihilation method

The electronic structure of Tb1-xYx single crystals is investigated by measuring the angular distribution of annihilation photons. An alteration of the Fermi surface for yttrium concentrations x<0.4 is observed on the basis of the changes in the characteristic features of the angular distribution functions related to the shape of the electron momentum distribution function. The contributions of the s- and d-electrons to the valency band are estimated. It is shown that the change in the wave vector of the helical magnetic structure, which occurs on alloying terbium and yttrium, depends on the change in the thickness of the ''band'' in the hole Fermi surface