Abstract
The lower and the upper critical fields Hc1 and Hc2, and the slope of magnetization at Hc2, (∂M⁄∂H)c2, are calculated in ferromagnetic superconductors. The theory takes account of the electromagnetic and the s-f exchange interactions between conduction electrons and localized f-electrons. When temperature decreases, (∂M⁄∂H)c2 in the mixed state increases and diverges at a certain temperature. This indicates that below this temperature, the transition at Hc2 is of a first order. Near the spin ordering temperature, Hc2 decreases more rapidly than Hc1 with decreasing temperature. The theoretical results are compared with experimental results in single crystals ErRh4B4 in detail.
