Crossover from Positive to Negative Magnetoresistance in a Spinel

摘要

A correlation between the magnetic and electrical response of a material is an essential property in a diverse range of technological applications, including magnetic sensors such as read head devices in computer hard disks. Recent advances in the science of modern materials have identified systems such as the manganate perovskites and pyrochlores that show potentially useful magnetoresistance (MR) effects. Here we report highly unusual magnetotransport behavior with MR > 80% in the spin glass-like material Zn_(0.95)Cu_(0.05)Cr_2Se_4, which undergoes a field-induced transition to a long-range ordered ferromagnet. The magnetoresistance changes sign with temperature, demonstrating a new mechanism for colossal magnetoresistance (CMR) that is particularly sensitive to low magnetic fields.