Colossal magneto-resistive relaxation effects in La0.9Ce0.1Fe12B6.

The study of the magnetic, electronic transport, and magnetotransport properties of La0.9Ce0.1Fe12B6 itinerant-electron system has been performed by combining magnetization, electrical resistivity, and magnetoresistance experiments. Along with the antiferromagnetic (AFM) ordering at TN = 35 K, two consecutive magnetic transformations, antiferromagnetic–ferromagnetic (AFM–FM) and ferromagnetic–paramagnetic (FM–PM), occur upon heating under certain magnetic field values. At fixed temperatures, it is revealed that both AFM and PM phases can be converted into the FM phase irreversibly and reversibly via a first-order metamagnetic transition associated with a large hysteresis. Below 8 K, the metamagnetic transition is discontinuous, manifesting itself by multiple sudden jumps in magnetoresistance and magnetization. A giant negative magnetoresistance effect of about −78% is found. We further demonstrate that the time dependencies of the electrical resistivity and the magnetization exhibit colossal spontaneous steps after an incubation time in conditions where both the applied magnetic field and temperature are constant. Another intriguing observation in the phase diagram is the presence of a critical point at the crossover of the three distinct PM, FM, and AFM magnetic states. [ABSTRACT FROM AUTHOR]