Electrical Probing of Magnetic Phase Transition and Domain Wall Motion in Single-Crystalline Mn₅Ge₃ Nanowire

Abstract

In this Letter, the magnetic phase transition and domain wall motion in a single-crystalline Mn(5)Ge(3) nanowire were investigated by temperature-dependent magneto-transport measurements. The ferromagnetic Mn(5)Ge(3) 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 Mn(5)Ge(3) 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 Mn(5)Ge(3) 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 the Mn(5)Ge(3) lattice. Furthermore, temperature-dependent magneto-transport measurements demonstrated a hysteretic, symmetric, and stepwise axial magnetoresistance of the Mn(5)Ge(3) nanowire. The interesting features of abrupt jumps indicated the presence of multiple domain walls in the Mn(5)Ge(3) 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.

Strain-induced switching between noncollinear and collinear spin configuration in magnetic Mn5Ge3 films

“…It is worth noting there is another small deformation (kind of cusp) in the d/dT curve at TI  72 K beside the well-visible transition at TC. Such a cusp is commonly observed in Mn5Ge3 thin films and nanostructures but has not been shown in bulk crystals [19,20,31]. The appearance of such a cusp in the d/dT curve is often related to the emergence of a new magnetic ordering.…”

“…The competing interactions between the AFM coupling between Mn2 and the FM coupling between Mn1 atoms stabilize noncollinear spin configurations [17,18]. The transition temperature from collinear to noncollinear magnetism in Mn5Ge3 is 70±5 K [19,20] which is usually explained by similar lattice distortions observed in Mn5Si3 [21][22][23]. Yet there is no convincing explanation, why the noncollinear spin configuration appears in nanostructured Mn5Ge3 but not in bulk materials [16,19,20].…”

Electrical spin injection and transport in semiconductor nanowires: challenges, progress and perspectives

“…The easy-axis of the ferromagnetic Mn 5 Ge 3 contact is found to be along the nanowire axis because of the shape anisotropy. 81 For the spin injection measurement, an axial magnetic field was swept back and forth to change the relative magnetization directions of the spin injector and detector between parallel and anti-parallel states, representing low and high resistance states, respectively. Fig.…”

“…22 It is to be noted that the observed MR characteristics do not resemble typical spin valve signals with abrupt resistance steps, which correspond to the magnetization switching of the spin injector and detector successively. 79,80 This is likely due to the presence of multiple domains in the formed ferromagnetic contacts and a small difference in their coercive fields, 81 which is limited by the device structure and the fabrication process itself.…”

Three-dimensionally kinked high-conducting CoGe nanowire growth induced by rotational twinning

“…Transition metal germanide NWs have also exhibited excellent properties that can be used for many applications, including nanoelectronics, spintronics, and eld emitters. [15][16][17][18][19][20][21][22][23] However, complex phase formation behavior of the metal germanides makes it difficult to control the stoichiometric composition and crystallographic phase of the metal germanide NWs, resulting in a scarcity of literature for them. It is known that bulk CoGe of a 1 : 1 stoichiometric composition has unique properties such as low resistivity and catalytic properties for partial hydrogenation of acetylene.…”