How to introduce non-linear variable

I am trying to introduce a non-linear variable in my temperature-dependent superconductor model, saying alpha(T)=alpha0*T_bath/T. When i run it

Error:7248
Undefined value found

Details

Exception:
com.femlab.jni.FlNativeException: Undefined value found Solvermodel
Messages:
Undefined value found Solvermodel

Stack trace:
at solvermodel.cpp, row 1837, (Undefined value found in the stiffness matrix.
There are 201 equations giving NaN/Inf in the matrix rows for the variable H
at coordinates: (0.2), (0.200001), (0.200002), (0.200003), (0.200004), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns
)
at com.femlab.solver.FlSolver.femTime(Native Method)
at com.femlab.solver.FemTime.run(Unknown Source)
at com.femlab.server.FlRunner.run(Unknown Source)
at com.femlab.util.i.run(Unknown Source)
at com.femlab.util.aa.run(Unknown Source)

Anyone know how to introduce non-linear in comsol 3.5a?