Overdamped interlayer exchange coupling and disorder-dominated magnetoresistance in

Magnetization and magnetoresistance (MR) measurements are reported on superlattices consisting of alternate layers of 20 unit cell (u.c.) thick $\chem{La_{0.7}Ca_{0.3}MnO_3}$ ($\chem{LCMO}$) and n u.c. $\chem{LaNiO_3}$ ($\chem{LNO}$), where n varies from 1 to 10. The saturation field ($H_{\ab{s}}$) and remnant magnetization ($M_{\ab{r}}$) show antiferromagnetic (AF) interlayer coupling for $n\leq 2$ followed by an overdamped oscillatory behavior with a period of $\approx 4$$\un{u.c.}$ with the increasing n. The low-temperature MR of the AF-coupled superlattices is characterized by a steep increase up to a critical field ${H_{\ab{s}}}^*$ ($\approx H_{\ab{s}}$) followed by a $\sim H^\alpha$ ($\alpha