Magnetization recoil-curve overshoot and interaction plots in Co thin films

Recoil magnetization curves measured on Fe, Co and Ni films have recently been found to lie entirely and way outside the major hysteresis loop, a phenomenon referred to as a recoil-curve overshoot, RCO. A model of pairs of exchange-coupled grains with slightly-misaligned anisotropy axes has been able to reproduce key features of these films such as the collapse of the hard-magnetization axis with greatly enhanced remanent magnetization and coercivity, the RCO as well as kinks some major loops present near saturation. In the present work we employ an interaction plot technique in order to probe the nature of the interactions influencing the peculiar magnetization reversal. Our study on a 25-nm-thick magnetron-sputtered Co film reveals another unforeseen, in thin ferromagnetic films, features, disclosed in the vicinity of the collapsed hard axis where scissors-like magnetization reversal takes place-wholly negative interaction plots and hysteretic loops with positive recoil fields. Through model simulations we show that, contrary to the widespread notion, ferromagnetic intergrain coupling might be solely responsible for these puzzling features of ferromagnetic hysteresis.