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Two-dimensional transition metal dichalcogenides (TMDs) have drawn immense interest due to their strong spin-orbit coupling and unique layer number dependence in response to spin-valley coupling. This leads to the possibility of controlling the spin degree of freedom of the ferromagnet (FM) in thin film heterostructures and may prove to be of interest for next-generation spin-based devices. Here, we experimentally demonstrate the odd-even layer dependence of WS2 nanolayers by measurements of the ultrafast magnetization dynamics in WS2/Co3FeB thin film heterostructures by using time-resolved Kerr magnetometry. The fluence (photon energy per unit area) dependent magnetic damping (alpha) reveals the existence of broken symmetry and the dominance of inter- and intraband scattering for odd and even layers of WS2, respectively. The higher demagnetization time, tau m, in 3 and 5 layers of WS2 is indicative of the interaction between spin-orbit and spin-valley coupling due to the broken symmetry. The lower tau m in even layers as compared to the bare FM layer suggests the presence of a spin transport. By correlating tau m and alpha, we pinpointed the dominant mechanisms of ultrafast demagnetization. The mechanism changes from spin transport to spin-flip scattering for even layers of WS2 with increasing fluence. A fundamental understanding of the two-dimensional material and its odd-even layer dependence at ultrashort timescales provides valuable information for designing next-generation spin-based devices. Odd-even WS2 layer number dependent ultrafast demagnetization and damping are studied by varying the pump fluence.

The evolution of the Verwey transition in Fe₃O₄ and its properties are discussed in this chapter. On the discovery of the Verwey transition, it was proposed that a sharp change in resistance with the temperature is governed by the structural modification from cubic to monoclinic phase. However, with time, this transition has evolved with several complications in its origin because the significant variation in the transition temperature point was observed as compared to a single crystal when Fe₃O₄ thin film was deposited onto substrates. Thanks to material science where different substrates with several doping agents can be made, which ultimately affects the Verwey transition due to variable interface strain available via lattice mismatching. Further, the origin of unique antiphase boundary evolution in Fe₃O₄ and their effect on the structural, magnetic, vibrational, and electronic properties are discussed. Several techniques are involved to explain the most abundant material Fe₃O₄, which shows promising features in several applications such as resistive switching, wearable electronics, and biomedical.

We demonstrate that tungsten disulphide (WS2) with thicknesses ranging from monolayer (ML) to several monolayers can be grown on SiO2/Si, Si, and Al2O3 by pulsed direct current-sputtering. The presence of high quality monolayer and multilayered WS2 on the substrates is confirmed by Raman spectroscopy since the peak separations between the A(1g)-E-2g and A(1g)-2LA vibration modes exhibit a gradual increase depending on the number of layers. X-ray diffraction confirms a textured (001) growth of WS2 films. The surface roughness measured with atomic force microscopy is between 1.5 and 3 angstrom for the ML films. The chemical composition WSx (x = 2.03 +/- 0.05) was determined from X-ray Photoelectron Spectroscopy. Transmission electron microscopy was performed on a multilayer film to show the 2D layered structure. A unique method for growing 2D layers directly by sputtering opens up the way for designing 2D materials and batch production of high-uniformity and high-quality (stochiometric, large grain sizes, flatness) WS2 films, which will advance their practical applications in various fields.

To achieve a large terahertz (THz) amplitude from a spintronic THz emitter (STE), materials with 100% spin polarisation such as Co-based Heusler compounds as ferromagnetic layer are required. However, these compounds are known to loose their half-metallicity in the ultrathin film regime, as it is difficult to achieve L2(1) ordering, which has become a bottleneck for the film growth. Here, the successful deposition using room temperature DC sputtering of the L2(1) and B2 ordered phases of the Co2FeAl full Heusler compound is reported. Co2FeAl is used as ferromagnetic layer together with highly orientated Pt as nonferromagnetic layer in the Co2FeAl/Pt STE, where an MgO (10 nm) seed layer plays an important role to achieve the L2(1) and B2 ordering of Co2FeAl. The THz generation in the Co2FeAl/Pt STE is presented, which has a bandwidth of 0.2-4 THz. The THz electric field amplitude is optimized with respect to thickness, orientation, and growth parameters using a thickness dependent model considering the optically induced spin current, superdiffusive spin current, inverse spin Hall effect, and the THz attenuation in the layers. This study, based on the full Heusler Co2FeAl compound opens up a plethora of possibilities in STE research involving full Heusler compounds.

In this work, a detail study on the effectiveness of high substrate temperature (TS) during deposition versus in situ annealing of the films at high temperature (TA) after sputtering at room-temperature is compared with an objective to obtain Heusler alloy thin films of Co2FeAl (CFA) having optimally low alpha int (with an upper bound of 1.75 & times; 10-3) and 12-17% smaller MS by employing ion beam sputtering technique and Si(100) as substrates for current induced magnetization switching application. In each of the two series of CFA films, prepared with different choice of TS and TA (lying in 300-773 K range) were explored for optimally tailoring their structural, static and dynamic magnetization properties. Structural study revealed that although all the CFA films were polycrystalline but the post-deposition annealed films were structurally optimal with higher density (6.36 +/- 0.09 g/cm3) and lower interface roughness (0.48 +/- 0.03 nm) compared to the CFA films grown at high TS (6.23 +/- 0.06 g/cm3, 0.61 +/- 0.01 nm). In plane field-angle dependent longitudinal magneto optical Kerr effect (LMOKE) study revealed the existence of a coupling between the weak uniaxial and biaxial magnetic anisotropies present in these films, attributed to the employed deposition geometry. Ferromagnetic resonance (FMR) spectroscopy measurements, performed in both the geometries - in-plane as well as out of plane, revealed a lowest value of 1.19 (+/- 0.08) & times; 10-3 of alpha int in the film post-annealed at 773 K. In addition, the observed non-linear relation between the alpha int and the dynamical 'g'-factor suggests that the contribution of spin orbit interaction to the damping is far less compared to the damping contribution from the DOS present near the Fermi level. It is remarkable to note that the as-grown CFA films sputtered at room temperature exhibited a record lowest value of 1.73 (+/- 0.09) & times; 10-3 of alpha int. Attainment of such small value of Gilbert damping and having moderate magnetization in high spin polarized Co2FeAl Heusler films sputtered on the Si (100) substrate opens up their great application potential in future spintronics devices.

The transition metal dichalcogenide 1T-TaS₂ is known to exhibit a number of collective electronic states known as charge density wave (CDW) instabilities. Intriguing phenomena such as a large damping-like spin−orbit torque (SOT) have been reported in monolayer 1T-TaS₂ [Nano Lett. 2020, 20 (9), 6372−6380]. Probing of CDWs in monolayer thick 1T-TaS₂ has been an inconceivable task. Here, the temperature-dependent spin dynamics and the effect of CDWs in the 1T-TaS₂(monolayer)/Ni₈₁Fe₁₉(Py) (7 nm) heterostructure are reported. Employing ferromagnetic resonance, the effect of the different commensurate (C) and nearly commensurate (NC) CDW states on the spin dynamics during heating and cooling cycles has been characterized by use of the effective damping constant and the spin mixing conductance of the heterostructure. In addition, these CCDW and NCCDW states, which affect the SOT efficiencies due to damping- and field-like SOTs, have been evaluated by using angle-dependent planar Hall effect measurements in controlled cooling and heating cycles. Our findings provide a fundamental understanding of the effect of different CDW states on the spin dynamics in twodimensional 1T-TaS₂ monolayer interfaced Py.

We correlate the structural, electrical, and magnetotransport properties of co-sputtered Mn2-xCo1?xAl full Heusler alloy thin films (0 x 1.75) in terms of Co/Mn concentration variation concerning the spin gapless semiconducting (SGS) behavior. The alloy thin films are found to stabilize in B2 order for near stoichiometric films, i.e. (x = 0 and x = 1), with the gradual change in the ordering and lattice parameter through Mn concentration variation. Magnetization measurements in Mn2-xCo1?xAl thin films reveal the ferromagnetic and ferrimagnetic character for x = 1.75, 1.5, 1.25 & 1, and x = 0, 0.5 & 0.75, respectively. The longitudinal resistivity measurement revealed that the films exhibit semiconducting behavior with a change in sign of the temperature coefficient of resistance with temperature. The anomalous Hall conductivity values for the Mn2-xCo1?xAl thin films are extracted from the Anomalous Hall effect (AHE) measurements. The non-saturating positive MR (linear in H) is being reported for the first time in the Mn2CoAl thin films. The value of the AHE coefficient and positive MR together serve as a piece of experimental evidence for the SGS character in the thin film. The SGS behavior becomes predominant at higher Mn concentration. Highly resistive thin films with ferromagnetic (ferrimagnetic) character in Co2MnAl (Mn2CoAl) could be beneficial for semiconductor spintronics, where we need a good resistive element to match up with Silicon base substrate.

We report on optically induced, ultrafast magnetization dynamics in the Heusler alloy Co2FeAl, probed by time-resolved magneto-optical Kerr effect. Experimental results are compared to results from electronic structure theory and atomistic spin-dynamics simulations. Experimentally, we find that the demagnetization time (tau(M)) in films of Co2FeAl is almost independent of varying structural order, and that it is similar to that in elemental 3d ferromagnets. In contrast, the slower process of magnetization recovery, specified by tau(R), is found to occur on picosecond time scales, and is demonstrated to correlate strongly with the Gilbert damping parameter (alpha). Based on these results we argue that for Co2FeAl the remagnetization process is dominated by magnon dynamics, something which might have general applicability.

Structural and dynamic magnetization properties of Co₂MnAl (CMA) full Heusler alloy thin films grown on Si (100) substrate at different substrate temperatures (T_s) 30°C, 200°C, 300°C, 400°C and 500°C are investigated. XRD patterns revealed the formation of B2 partially ordered phase at T_s=200°C and above. Ferromagnetic Resonance (FMR) technique have been used to determine the damping constant (α), resonance field (H_r) and line width (ΔH) of recorded spectra and fitted by using Landau-Lifshitz-Gilbert (LLG) equation. The lowest damping constant was found to be 0.007±0.002 for the film grown at T_s=200°C. Films exhibit uniaxial magnetic anisotropy. Anisotropic damping constant α is calculated along the easy and hard axis. Along the two directions remarkable change (almost ∼59%) in α is observed.

Spin-orbit coupling (SOC) in two-dimensional (2D) materials has emerged as a powerful tool for designing spintronic devices. On the one hand, the interest in this respect for graphene, the most popular 2D material with numerous fascinating and exciting properties, is fading due to the absence of SOC. On the other hand, 2D transition metal dichalcogenides (TMDs) are known to exhibit rich physics including large SOC. TMDs have been used for decades in a variety of applications such as nano-electronics, photonics, optoelectronics, sensing, and recently also in spintronics. Here, we review the current progress in research on 2D TMDs for generating spin-orbit torques in spin-logic devices. Several challenges connecting to thin film growth, film thickness, layer symmetry, and transport properties and their impact on the efficiency of spintronic devices are reviewed. How different TMDs generate spin-orbit torques in magnetic heterostructures is discussed in detail. Relevant aspects for improving the quality of the thin film growth as well as the efficiency of the generated spin-orbit torques are discussed together with future perspectives in the field of spin-orbitronics.