Considering type-I superconductors (specifically the magnetisation curves), why can one assume that the magnetisation is zero when we consider a normal state (when $H>H_C$)?
EDIT: For clarification, I'm going through the first few chapters of Tilley and Tilley, and I'm trying to get my head around why they seem to assume this. Basically, I'm looking for an explanation of the Type-I magnetisation curve, as seen in this link here. This kind of graph appears quite a lot, but what I am yet to understand fully is why does a normal (non SC) state have zero average magnetisation. My guess is something to do with the 'average' nature of it?
EDIT2: The content in T+T was slightly poorly worded and confusing to the uninitiated. Thank you all for the clarification.