Electrical Probing of Magnetic Phase Transition and Domain Wall Motion in Single-Crystalline Mn(5)Ge(3) Nanowire
In this letter, the magnetic phase transition and domain wall motion in a single-crystalline Mn5Ge3 nanowire were investigated by temperature-dependent magneto-transport measurements. The ferromagnetic Mn5Ge3 nanowire was fabricated by fully germaniding a single-crystalline Ge nanowire through the solid-state reaction with Mn contacts upon thermal annealing at 450 °C. Temperature-dependent four-probe resistance measurements on the Mn5Ge3 nanowire showed a clear slope change near 300 K accompanied by a magnetic phase transition from ferromagnetism to paramagnetism. The transition temperature was able to be controlled by both axial and radial magnetic fields as the external magnetic field helped maintain the magnetization aligned in the Mn5Ge3 nanowire. Near the magnetic phase transition, the critical behavior in the 1D system was characterized by a power-law relation with a critical exponent of α = 0.07 ± 0.01. Besides, another interesting feature was revealed as a cusp at about 67 K in the first-order derivative of the nanowire resistance, which was attributed to a possible magnetic transition between two noncollinear and collinear ferromagnetic states in theMn5Ge3 lattice. Furthermore, temperature-dependent magneto-transport measurements demonstrated a hysteretic, symmetric, and stepwise axial magnetoresistance of theMn5Ge3 nanowire. The interesting features of abrupt jumps indicated the presence of multiple domain walls in theMn5Ge3 nanowire and the annihilation of domain walls driven by the magnetic field. The Kurkijärvi model was used to describe the domain wall depinning as thermally assisted escape from a single energy barrier, and the fitting on the temperature-dependent depinning magnetic fields yielded an energy barrier of 0.166 eV.