Ground-state spectroscopic properties of an amorphous holmium aluminosilicate exhibiting spin glass properties

Electron paramagnetic resonance (EPR), optically detected EPR and magnetic circular dichroism measurements have been performed on a 10% doped holmium amorphous aluminosilicate in the range 20-1.4K. This sample had previously been shown to exhibit spin glass properties (freezing temperature Tf=0.6K). The experimental data strongly suggest a random axial symmetry, with a low-symmetry distortion varying locally from site to site. An effective Hamiltonian H=g mu BHSz+AIzSz+2E(Sx2-Sy2) corresponding to a fictitious spin mod +or-1) allows the authors to account satisfactorily for the experimental spectra and leads to an estimate of both the parameters: g=8.8 and 0holmium aluminosilicate in the vicinity of the freezing temperature.