Modeling Magnetostriction - mod1.Azy variable

Hello
I'm modeling magnetostriction in a laminated core in 2D. I have studied the '''non linear_magnetostriction'' model in COMSOL and have compare my model with that. In my model everything looks alright but the model does not run and returns the following error:

Fail to evaluate variable Jacobian.
- Variable: mod1.Azy
- Geometry: 1
- Domain: 2 ,5 , . . .
-Feature: stationary solver 1(sol1/s1)

Anybody has any comments?
Regards
Hamid