Tunable Resistance or Magnetoresistance Cusp and Extremely Large Magnetoresistance in Defect-Engineered HfTe 5 − δ Single Crystals

The electrical transport behaviors of novel materials under the external magnetic field B, especially the large or tunable magnetoresistance (MR) effect, are of broad importance in both fundamental science and applications. Here three kinds of HfTe5 crystals with varied Te-deficiency concentrations are synthesized under different growth conditions, and they demonstrate distinct electrical and magnetotransport properties. The temperatures of the resistivity cusp or MR cusp of the as-grown HfTe5-delta (delta = 0.02, 0.08, 0.13) crystals are tuned from 25 to 90 K. The maximum MR of these three HfTe5-delta crystals, under 2 K and 9 T B, are 1.52 x 10(3)%, 2.63 x 10(4)%, and 6.91 x 10(3)% for sample SI (HfTe4.98), SII (HfTe4.92), and SIII (HfTe4.87), respectively. The fitting of Hall data by the two-carrier model suggests that the extremely large MR effect of sample HfTe 4.92 measured at 2 K is attributed to the cooperative action of the high mobility and the coexistence of the electron and hole carriers. Our work provides a viable route to tune superior MR properties in similar compounds through defect engineering, which may be promising to develop magnetic memory sensor devices.