Preeti A. Bhobe

We present a systematic study of the structural, magnetic, and transport properties of the cubic Heusler alloy Mn _1.7 Fe _1.3 Si. Room-temperature x-ray diffraction and temperature-dependent neutron powder diffraction confirm long-range cubic L2 ₁ ordering, with no crystallographic phase transition down to 20 K. Magnetization measurements reveal a paramagnetic–ferromagnetic/ferrimagnetic transition at T C = 85 K, followed by a spin-reorientation transition between 65 K and 55 K. Neutron diffraction shows that long-range antiferromagnetic (AFM) order develops only below 55 K, stabilizing a canted AFM ground state. Anomalies in the temperature dependence of the unit-cell volume across magnetic transitions provide clear evidence of magnetoelastic coupling. Electrical resistivity measurements confirm metallic behaviour. At low temperatures, magnetization and magnetotransport data reveal a field-induced metamagnetic transition accompanied by irreversibility, metastability, and magnetic phase coexistence, leading to a low-field coexistence region in the H − T phase diagram below 2.5 T. Notably, the metamagnetic transition is purely magnetic and occurs without any structural transformation. These results clarify the complex magnetic behaviour of Mn _1.7 Fe _1.3 Si and highlight the role of spin–lattice coupling in Mn-based Heusler alloys.

We report an observation of metal-insulator transition in a thin film of SnSe2. The room-temperature carrier concentration of the SnSe2 film was increased by electrostatic doping to 1.14×1013cm−2. A crossover from the insulating phase to the metallic state was clearly observed. The low-temperature charge transport mechanism is governed by two-dimensional variable-range hopping. This mechanism is influenced by band bending and gap states introduced by selenium vacancies. At low temperatures, the mobility is primarily limited by charged impurities, while at higher temperatures, it follows a power-law dependence, μ=T−γ, indicating a dominance of electron–phonon scattering. The application of a gate field shifts the Fermi level toward the conduction band, and at sufficiently high temperatures, this drives the system into a metallic state. Our findings offer insights into the charge transport mechanisms in SnSe2 field-effect transistor, this understanding will allow for the optimization of other 2D materials for advanced electronic device applications.

In this work, we report the synthesis and comprehensive characterization of pristine and Fe-doped SnSe ₂ single crystals, revealing how light Fe doping enhances photoconductivity and induces magnetism in this layered 2D material.

Heusler alloys are typically metallic, with high electrical conductivity and a positive temperature coefficient of resistivity. Finding semiconductor‐like behavior, where resistivity increases with decreasing temperature, suggests unexpected changes in the scattering mechanisms of the charge carriers. Herein, the temperature‐dependent behavior of electrical resistivity, ρ ( T ), of Fe ₂ Ti _0.5 Mn _0.5 Sn is investigated. The ρ versus T plot is semiconductor‐like, showing a quasilinear behavior over an extended temperature region. This unusual behavior of ρ ( T ) can be described within the Cote–Meisel formalism based on the diffraction model of strongly disordered metals. Further, below 30 K the electrical resistivity obeys a T ^1/2 law, which is explained by the weak localization effect. The negative magnetoresistance supports the weak localization scenario. X‐ray diffraction and magnetization measurements also confirm the presence of strong disorder, strain‐induced tetragonal distortion, and a small fraction of the secondary hexagonal Fe ₂ MnSn phase in the prepared composition. Together, these features provide a natural explanation for the deviation of transport and magnetic properties from those predicted for the ideal ordered L2 ₁ structure. The current study discusses the systematic approach to understanding the anomalous transport property of disordered Heusler alloy.

This work examines the influence of thickness on the electrical transport properties of mechanically exfoliated two-dimensional SnSe$_2$ nanosheets, derived from the bulk single crystal. Contrary to conventional trend observed in two-dimensional systems, we find a semiconducting to metallic resistivity behavior with decreasing thickness. The analysis of low-temperature conduction indicates an increased density of states at Fermi-level with decreasing thickness, which is further corroborated by gate bias dependent conductance measurement. The enhanced conductivity in thinner flake is attributed to the n-type doping arising from surface defect states. The presence and evolution of these defect states with thickness is probed by thickness-dependent room-temperature Raman spectroscopy. Our study provides insights into the thickness-dependent electronic transport mechanism of SnSe$_2$ and the crucial role of defect states in governing the observed conductivity behavior.