Is it necessary to have work experience for doing MBA from Stanford and Harvard University?

Yes. You need to have a minimum 3 year work experience for getting into the MBA program at Stanford and Harvard University both. 

So the best alternative for a student like you who wants to study management but without any work experience is to do a MiM. A MiM is equivalent to an MBA degree as it teaches you the same knowledge and skills. The only difference between the two is that a MiM degree is more relevant to students without any work experience as it introduces them to the corporate world in the right way. You being a fresh graduate should definitely consider doing a MiM rather than MBA. 

Let me know if you need any help with the universities that you can apply to or the admission process and I shall provide you with the detailed information.