Negative magnetoresistance in crystals of the paramagnetic intercalation compound Mn_xTiS₂

Transverse magnetoresistance for paramagnetic Mn_xTiS₂ (0.02<~x<~0.25) crystals has been measured at three fixed temperatures 77, 4.2, and 1.8 K at fields up to 31 T using a compact home-made pulsed magnet. We have found a large negative magnetoresistance Δρ/ρ₀ at low temperatures. For example, Δρ/ρ₀ for x=0.25 is of the order of 40% at 1.8 K and 31 T and shows a cubic dependence on the magnetization M, Δρ/ρ₀∝-(M/M_s)³ (M_s: saturation magnetization), rather than a quadratic dependence Δρ/ρ₀∝-(M/M_s)² which is found for many ferromagnetic materials. Qualitative discussions for the negative magnetoresistance in the layered structure of Mn_xTiS₂ are given by considering a transport process through host TiS₂ “intralayers” and its “interlayers” via intercalated Mn atoms in the van der Waals gaps. The magnetic field dependence of the negative magnetoresistance can be reasonably explained by the existing spin-fluctuation theory.