Hysteresis and Anisotropic Magnetoresistance in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$

The out-of-plane resistivity ($rho_c$) and magnetoresistivity (MR) are studied in antiferromangetic (AF) $Nd_{2-x}Ce_xCuO_{4}$ single crystals, which have three types of noncollinear antiferromangetic spin structures. The apparent signatures are observed in $rho_c(T)$ measured at the zero-field and 14 T at the spin structure transitions, giving a definite evidence for the itinerant electrons directly coupled to the localized spins. One of striking feature is an anisotropy of the MR with a fourfold symmetry upon rotating the external field (B) within ab plane in the different phases, while twofold symmetry at spin reorientation transition temperatures. The intriguing thermal hysteresis in $rho_c(T,B)$ and magnetic hysteresis in MR are observed at spin reorientation transition temperatures.