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

Abstract VS 2 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 VS 2 consistent with the Raman spectrum and high-resolution transmission electron microscopy study. X-ray photoelectron spectroscopy confirmed the formation of VS 2 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 VS 2 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mi>M</mml:mi> <mml:mrow> <mml:mtext>saturation</mml:mtext> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> of 3.25 memu g −1 at 50 K which gradually decreased with increase in temperature. The coercivity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mi>H</mml:mi> <mml:mtext>C</mml:mtext> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> , 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mi>θ</mml:mi> <mml:mi>p</mml:mi> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mn>3.124</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext>K</mml:mtext> </mml:mrow> </mml:math> 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 VS 2 as well as its Curie temperature for its applicability in spintronics devices.