Anomalous field dependence of magnetoresistance in Fe/Gd multilayered ferrimagnets

The magnetoresistance of Fe/Gd ferrimagnetic multilayered films prepared by sputtering was investigated. The longitudinal magnetoresistance ρl increases first, followed by a deep decrease, and then increases again, with an increasing applied field. The transverse magnetoresistance ρt behaves in an opposite manner such that ρl and ρt play a crossover at an intermediate field. This new type of field dependence of ρl and ρt can be explained in terms of the spin flop of artificial ferrimagnetism which gives rise to an anomalous up-turn curve in magnetization versus field.