Unprecedented magnetoresistance in Cd-substituted Tl2Mn2O7 pyrochlores

Abstract

Moderate pressure techniques (P=20 kbar) have been used to prepare Tl2−xCdxMn2O7 (0⩽x⩽0.4) pyrochlore-like materials. The x=0.2 compound has been characterized by neutron powder diffraction, magnetic, magnetotransport, and Hall measurements. This material is ferromagnetic below TC=110 K. Both electrical resistance and magnetoresistance (MR) are enhanced with respect to stoichiometric Tl2Mn2O7, due to the drastic reduction in the number of carriers (electrons) induced by hole doping. MR(0.5 T) is higher than 106% at 120 K, and MR(9 T) is 30% at room temperature. We show that hole doped derivatives of Tl2Mn2O7 are promising candidates in which to search for large bulk magnetoresistance.