Magnetic susceptibility of fluoride glasses with 3d and 4f elements

The low field ac magnetic susceptibility has been studied as a function of temperature and frequency in a series of fluoride glasses containing Mn²⁺, rare-earth ions, or an admixture of the two types. All glasses exhibit magnetic freezing in the ⁴He or ³He temperature ranges, but the nature of the freezing appears to depend on the local anisotropy. In the case of Mn²⁺ or Mn²⁺ -Gd³⁺ ions, a sharp freezing analogous to that in CuMn was observed. For Ln³⁺ or Mn²⁺ -Ln³⁺ ions (Ln=Dy, Ho), the observed progressive freezing could be of a dynamic nature.