Giant Negative Magnetoresistance Effect in La_1-xPr_xFe₁₂B₆ (x = 0.05, 0.15) Compounds

LaFe₁₂B₆ is a rare itinerant-electron metamagnet, and substitution of rare-earth elements can significantly influence its field-induced phase transition and magnetocaloric effects. However, how such elemental substitution modulates its magnetoelectrical transport properties remains unclear. Here, we report electrical transport measurements on La_1-xPr_xFe₁₂B₆ (x = 0.05, 0.15) compounds between 3 and 150 K in fields up to 90 kOe using the four-wire method on characterized polycrystals containing 9.5 and 3.8 wt.% Fe₂B, respectively. Samples were thermally reset and demagnetized prior to each isothermal test. At 3 K, magnetoresistance (MR) reproduces the following magnetization features: two abrupt MR drops at 41 and 67 kOe for x = 0.05. Below the first critical field, the MR becomes positive (+20% for x = 0.05, +5% for x = 0.15) and then drops abruptly. The steps broaden and merge into a smooth response as the temperature rises. The largest negative MR values measured, -78% (x = 0.05, 40 K) and -68% (x = 0.15, 70 K), lie close to the corresponding magnetic transitions. The incomplete resistivity recovery observed after field removal-most pronounced at low temperature for both compositions and vanishing near 120 K-reveals a kinetically arrested transformation. By combining magneto-transport with magnetization measurements, the giant negative magnetoresistance (up to -78%) of La_1-xPr_xFe₁₂B₆ closely tracks the stepwise metamagnetic transition, via field-suppressed spin-disorder scattering, with the effect extending above T_C for the Pr-richer composition.