This is a question for Exchemist mainly but other feel free to answer, what chemically about superconductors determines the maximum Magnetic Field Strength of Superconductors because Superconductors in theory have a zero electrical resistance but in practice have a very small electrical resistance many orders of magnitude lower than normal conductors I wanted to know chemically what determines these factors what about these chemicals allow lower resistance and higher magnetic field strength? Furthermore it is said that Iron Superconductors can reach magnetic field strengths of 120 T which is superconducting while Cuprates can only reach 15 T, so in exacting details what causes this effect which is a function on electrical resistance of the superconductor? Does that book have a section about superconductors because I understand the physics of magnetism in normal situations. The Problem is when the theoretical and experimental resistance of superconductors doesn't match as they in theory are supposed to have a zero electrical resistance which would yield a infinite magnetic field strength but however in practice you can only achieve a certain amount of magnetism because of the small electrical resistance of the superconductor. Basically, I think I need a chemistry book about superconductors. I need to know the chemical reason to why this small resistance exists rather than the magnetic component as I know the source of the magnetism which is current. smt359-1-006i.jpg Limits-of-Superconductivity.jpg superconductivity-8-638.jpg But the question is what causes Critical Magnetism Field Density and Critical Current Density chemically? So I guess what is Magnetic field H0 or B0 a function of chemically is the question.