Pressure-tuned colossal magnetoresistance effect in n-type CdCr2Se4

The p-type CdCr2Se4 exhibits semiconducting conductivity while n-type CdCr2Se4 displays a semiconductor–metal transition and a concomitant colossal magnetoresistance near the Curie temperature. Here, we investigate the pressure effect on the conductivity for both types of compounds. We show that the resistance of p-type sample decreases continuously upon compression, while the semiconducting behavior dominates up to 27.9 GPa. For the n-type sample, the semiconductor-metal transition is suppressed gradually with the increase in pressure; meanwhile, the magnetoresistance becomes less and less pronounced and is negligible at 9.2 GPa. Combined with in situ high-pressure magnetization, x-ray diffraction, and Raman spectra investigations, a ferromagnetic ground state is deduced in the pressurized n-type CdCr2Se4 before the structural transition, which is in stark contrast to the pressure effect on n-type HgCr2Se4.