Mechanical magnetoresistance in broken cold-pressed CrO2 powder sample

Large negative magnetoresistance (MR)(|ΔR/R|=|[R(H)-Rmax]/Rmax|>50%) has been observed in the broken cold-pressed CrO2 powder samples near the room temperature, which is ascribed to the magnetic field-induced mechanical contact variation. This large, room-temperature negative MR might easily lead to a wrong conclusion that the spin-polarization is still very high at high temperatures. This observation may also point to the possibility to develop field sensors based on the mechanical MR.