Thermal hysteresis and anisotropy in the magnetoresistance of antiferromagnetic Nd2-x Cex Cu O4

The out-of-plane resistivity ( ρ_c ) and magnetoresistivity (MR) are studied in antiferromangetic (AF) Nd_2-x Ce_x Cu O₄ single crystals, which have three types of noncollinear antiferromangetic spin structures. The apparent signatures are observed in ρ_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 the striking features 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 ρ_c (T,B) and magnetic hysteresis in MR are observed at spin reorientation transition temperatures.