ESR surface probing of magnetostatics in high-Tc superconductors

We show that magnetic properties of the mixed state of high-Tc superconductors can be quantitatively studied by use of ESR surface probing. We demonstrate that the ESR properties depend crucially on the distance of the ESR probe from the surface. We focus in this paper on the long-distance limit where the ESR-probe-line position is mostly sensitive to the first-order moment of the magnetic-induction distribution at the surface of the sample. A simple magnetostatic model is developed that shows the ESR probe line depends on the field-cooled magnetization when the system is reversible and on the field-cooling procedure when the system is irreversible. We present experimental results that confirm the validity of our analysis.