Magnetostructural transitions from low-temperature TiNiSi-type phases to high-temperature Ni₂In-type phases had been observed in some MnCoGe-based and MnNiGe-based intermetallic systems. In this work, the TiNiSi-to-Ni₂In-type magnetostructural transitions, which are associated with large changes in magnetization and large anisotropy lattice distortion, were obtained in a Ge-free system Mn_0.5Fe_0.5Ni(Si,Al) in the vicinity of room temperature. Thermal-cycling-dependent properties were observed in the as-prepared bulk polycrystalline samples. This phenomenon could be attributed to the presence of anisotropy internal stress and its release by spontaneously cracking across the thermally activated magnetostructural transitions.

In this work, we studied ac responses of T-stub structures that are composed of armchair and zigzag graphene ribbons. Compared with uniform graphene ribbons, the T-stub structures show extraordinary properties. The ac responses of armchair and zigzag T-stub structures show different behaviors for different edge configurations. The imaginary part of admittance can be capacitive or inductive depending on the Fermi energy and structural parameters. These properties provide deeper understanding of dynamic processes of electrons in graphene-based nanodevices.

Phosphorene, one of the graphene counterparts, is believed to have promising potential to be utilized in nanoelectronics due to its significant properties. Phosphorene has a nonplanar puckered structure with high anisotropy, which enables the elastic strain or external field to tune its electronic structure. In this work, we propose a nanodevice model based on an armchair phosphorene nanoribbon (APNR) with normal-metal electrodes and study the tuning effect of elastic strain and electric field on the electronic transport properties. We first confirm that the APNR can be driven to be of metallic conduction with linear dispersion around the Fermi level, by applying a critical compressive strain. After applying a perpendicular electric field, the APNR turns out to be a band insulator. Furthermore, we calculate the dc conductance and density of states (DOS) of the nanodevice, where the APNR is connected to normal-metal electrodes. The numerical results show that in the absence of an electric field, the nanodevice possesses peak values of conductance and DOS at the Fermi level. Once the electric field is applied, a gap emerges around the Fermi level in the conductance, which suggests that the nanodevice is turned off by the external electric field. Our investigation on the present system could be useful in the development of a field-effect nanodevice based on monolayer phosphorene.

Dynamic conductance of nanocircuit, which demonstrates dc and ac transport properties, is regarded as vital indicator for device feature. With the help of nonequilibrium Green's function technology and Buttiker's ac transport theory, we present dynamic conductance in L-shaped graphene nanosystems (LGNSs). It is found that electronic transport is highly sensitive to the geometric feature as well as the size of LGNSs. The armchair edge lead determines whether LGNS shows ac response or not around Dirac point. The increase of width of zigzag edge lead suppresses dc conductance and induces capacitive responses at the anti-resonance states. This is due to large dwell time originated from edge state in zigzag edge lead. In the energy region far away from Dirac point, LGNS responds inductively with the transportation channel opens. Behaviors of dynamic conductance at Dirac point and anti-resonance states are discussed by interesting spacial-resolved local density of states.

Topological configurations play an important role in graphene nanoribbon based devices. In this work, the Büttiker’s ac transport theory is used to study an asymmetric three terminal graphene nanoribbon structure. With the help of Green’s function and related parameters, we show that the topological asymmetries can form capacitive and inductive junctions in this three terminal structure. The transport properties are sensitive to the geometric features of the branches of the junctions and the coupling positions. It is believed that this kind of structure can be useful for the future nanoelectronic devices.