Insights into the magnetic signature in VS2 nanosheets for spintronics applications: an experimental and ab initio approach

Abstract

VS2 nanosheets were synthesized using a facile hydrothermal method with varying hydrothermal durations for detailed study of their magnetic properties for spintronics applications. The (001) peak near 15.45° in the x-ray diffraction pattern confirmed the formation of the hexagonal phase of VS2 consistent with the Raman spectrum and high-resolution transmission electron microscopy study. X-ray photoelectron spectroscopy confirmed the formation of VS2 with the +4 oxidation state of V. Morphology was determined by field emission scanning electron microscopy that showed the morphological transition from nanoflowers to nanosheets with increase in the hydrothermal duration from 16 h to 24 h. The VS2 nanosheets were subject to magnetic measurements using a superconducting quantum interference device. The isothermal magnetization versus magnetic field plot showed typical hysteresis behaviour at low fields with maximum saturation magnetization of 3.25 memu g−1 at 50 K which gradually decreased with increase in temperature. The coercivity , however, increased with increase in temperature, hinting at the possible short range of the existing ferromagnetic (FM) order. The field-cooled and zero-field-cooled curves showed a lack of FM clustering. Fitting of the magnetization versus temperature plot showed the formation of a mixed magnetic phase, that is both a paramagnetic (PM) phase (at high fields) and a FM phase (at low fields). The PM Curie temperature obtained from the fitting hinted at canted antiferromagnetic order. Magnetoresistance (MR) measurement in a current parallel to the field configuration revealed a negative MR of 10.4%. Further, density functional theory and Monte Carlo simulations based on the Metropolis algorithm were used to study the layer-dependent electronic band structure of VS2 as well as its Curie temperature for its applicability in spintronics devices.