Novel Colossal Magnetoresistance in Sodium Chromium Oxide

Abstract

Recently, a new calcium-ferrite type chromium oxide, NaCr₂O₄, was synthesized under high pressure of 7 GPa, and was found to show the unconventional colossal magnetoresistance (CMR) effect below the canted-antiferromagnetic transition temperature of T_N = 125 K. In this paper, in addition to crystal structure data and magnetic properties, we show the temperature dependence of the electrical resistivity under 0, 3, and 9 T and the field dependence of magnetoresistance ratio at 45, 60, and 80 K. These clearly support the unconventional nature of the CMR effect. We discuss the existence of holes on oxygen ions, and propose a possible mechanism of CMR in NaCr₂O₄, in which the spin frustration and the holes play an important role. A guide to find new CMR compounds is also presented.