Dear Kadhim

I guess you are looking back at our old data on Er in amorphous Y-Cu alloys?  This was the only case where we saw a well defined crystal field excitation with neutron spectroscopy.  The problem in calculating the heat capacity in this case is we have only one excitation, whereas for an Er ion in low symmetry surroundings we might expect eight doublets (J=15/2), and therefore seven excitations.  Unfortunately it is impossible to model this realistically since we do not know much about the local environment in an amorphous material.  We don't know, for example, the degeneracy of the ground state or excited state involved in the observed excitation.  If you have heat capacity data with a well defined  Schottky anomaly you could attempt to model it with a simple two-level system using the known excitation energy, assuming different degeneracies for the two levels.

I hope this helps.  

Best wishes

Brian Rainford

Dear Prof. Rainford,

Thank you very much for your answer.

I will send you details of the analysis of our old data to your e-mail ([email protected]).

Regards