Specific features of the formation of atomic magnetic moments in amorphous films RE–Co (RE = La, Gd, Tb)

A systematic investigation of the magnetic properties of amorphous films in (RE)$_x$Co$_{100-x}$ binary systems in the ground state with rare-earth elements (RE) of different types has been performed. The concentration dependences of the average atomic magnetic moments of cobalt $(m_{\mathrm{Co}})$, gadolinium $(m_{\mathrm{Gd}})$, and terbium $(m_{\mathrm{Tb}})$ have been determined from the analysis of the spontaneous magnetization of the films with a nonmagnetic rare-earth element (La), a rare-earth element with a spherical electron shell (Gd), and a rareearth element with a large orbital magnetic moment (Tb). It has been shown that, in the range 0 $<x<$ 50 at%, the magnetic moment $m_{\mathrm{Co}}$ decreases from 1.7 $\mu_{\mathrm{B}}$ to zero, the magnetic moment $(m_{\mathrm{Gd}})$ remains unchanged and almost coincides with the magnetic moment of the free atom (7 $\mu_{\mathrm{B}}$), and the value of $m_{\mathrm{Tb}}$ decreases monotonically, but the rate of decrease depends on the method of the sample preparation. The revealed regularities are associated with the concentration change in the electronic structure of cobalt and with the specificity of the magnetic structure of the films, which has a ferromagnetic, ferrimagnetic, or sperimagnetic character for samples containing La, Gd, or Tb, respectively.