UPDATE
It seems that the .set() method is working but for some reason the new object created is returning the name and ID as undefined. Might be a bug with ember-model perhaps.
The best solution for the moment would be to have 2 save methods, one on the edit controller as you currently do and then adding a different save method for creating a new department.
App.NewController = Ember.ObjectController.extend({
save:function(){
var newDep = App.Department.create({name: this.get('name')});
newDep.save();
this.get('target').transitionTo('department', this.get('model'));
}
});
Here is a jsbin with the New controller added - http://jsbin.com/EVUlOyo/1/edit
End Update
It looks like when you are creating the record it is not setting the name value correctly on the object.
I changed the following -
newDepartment = self.get('model');
newDepartment.set('name',this.get('name'));
newDepartment.save();
to -
var newDep = App.Department.create({name: this.get('name')});
newDep.save();
Here is an updated jsbin also http://jsbin.com/EkEXInO/1/edit
Hope that helps and works for you.