O B A V I J E S T
GAURAV PRANSU
održat će znanstveni kolokvij (doktorski seminar) iz Fizike kondenzirane tvari pod naslovom:
Complexities of the Electronic and Magnetic Properties of Intercalated 2H-NbS₂ and 2H-TaS₂
Transition-metal dichalcogenides (TMDs) are layered materials that exhibit a rich variety of physical phenomena, including charge density waves (CDWs) and superconductivity. Their van der Waals gaps can be intercalated with 3d magnetic atoms, which can suppress CDW order and superconductivity while inducing magnetic order. The resulting metallic systems provide an opportunity to investigate the interplay between itinerant electrons, localized magnetic moments, and geometric frustration, giving rise to unconventional magnetic and transport phenomena with potential applications in spintronics. Their magnetic ground states are also highly sensitive to intercalant concentration and external pressure, leading to significant changes in magnetic and transport properties. However, systematic studies linking intercalant ordering, magnetic order, and electronic transport in single crystals remain limited.
In this doctoral research, single crystals of NiₓNbS₂, CoₓTaS₂, and Co₁/₃NbS₂ were grown by chemical vapor transport and characterized using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction, magnetization, and electrical transport measurements.
For NiₓNbS₂, single crystals covering a broad range of Ni concentrations (0.1 < x < 0.57) were investigated. EDX and X-ray diffraction confirm the Ni stoichiometry. Magnetization measurements indicate predominantly antiferromagnetic order across the investigated composition range. The Néel temperature varies non-monotonically with Ni concentration. Particular attention was given to Ni₀.₂₅NbS₂ and Ni₀.₃₃NbS₂, which exhibit well-defined commensurate superstructures. These compositions were further investigated.
In CoₓTaS₂, crystals with Co concentrations below (x = 0.313) and above (x = 0.34) the nominal x = 1/3 composition exhibit markedly different magnetic and transport behavior. The underdoped crystal develops a weak ferromagnetic component within the antiferromagnetic phase below TN2 ≈ 26 K. This behavior is accompanied by magnetic switching and hysteresis in both the magnetization, M(H), and the magnetoresistance. In contrast, these features are absent in the overdoped crystal, highlighting the strong sensitivity of the magnetic and transport properties to Co concentration.
Finally, the electrical transport properties of Co₁/₃NbS₂ were investigated under hydrostatic pressures of up to 7.5 GPa using a diamond-anvil cell. Although no distinct transition is observed over the investigated pressure range, the progressive suppression of the concave curvature of the resistivity indicates a pressure-induced modification of the charge transport, reflecting changes in the relevant scattering mechanism.
Taken together, the results demonstrate that the magnetic and transport properties of intercalated TMDs depend strongly on the intercalant species, concentration, and applied pressure. In NiₓNbS₂, antiferromagnetic order persists across the investigated concentration range (0.1 < x < 0.57), whereas in CoₓTaS₂, a slight Co deficiency relative to x = 1/3 is associated with a weak ferromagnetic component and magnetic switching, which are absent in the Co-rich crystal. In Co₁/₃NbS₂, pressures up to 7.5 GPa do not induce a transition in the electrical resistivity but instead modify charge-carrier scattering.
Seminar će se održati u ponedjeljak, 26. rujna 2026. godine u 14:00 sati u predavaonici F-201 Fizičkog odsjeka Prirodoslovno-matematičkog fakulteta Sveučilišta u Zagrebu.
Pozivaju se studenti doktorskog studija Fizike, smjer Fizika kondenzirane tvari, da prisustvuju seminaru, ako nisu spriječeni.
Voditelj smjera:
Prof. dr. sc. Ana Akrap, v.r.
Pristupačnost
