Magnetization dynamics due to field interplay in field free spin Hall nano-oscillators

Spin Hall nano oscillators (SHNOs) have shown applications in unconventional computing schemes and broadband frequency generation in the presence of applied external magnetic field. However, under field-free conditions, the oscillation characteristics of SHNOs display a significant dependence on the effective field, which can be tuned by adjusting the constriction width, thereby presenting an intriguing area of study. Here we study the effect of nano constriction width on the magnetization dynamics in anisotropy assisted field free SHNOs. In uniaxial anisotropy-based field-free SHNOs, either the anisotropy field or the demagnetization field can dominate the magnetization dynamics depending on the constriction width. Our findings reveal distinct auto-oscillation characteristics in narrower constrictions with 20 nm and 30 nm constriction width compared to their wider counterpart with 100 nm width. The observed frequency shift variations with input current and constriction widths stem from the inherent nonlinearity of the system. The interplay between the B_demag and B_anis, coupled with changes in constriction width, yields rich dynamics and offers control over frequency tunability, auto oscillation amplitude, and threshold current. Notably, the spatial configuration of spin wave wells within the constriction undergoes transformations in response to changes in both constriction width and anisotropy. The findings highlight the significant influence of competing fields at the constriction on the field-free auto oscillations of SHNOs, with this impact intensifying as the constriction width is varied.Comment: 25 pages, 11 figure

Spin Pumping in Asymmetric Fe50Pt50/Cu/Fe20Ni80 Trilayer Structure

Herein, spin transport dynamics across asymmetric Fe50Pt50/Cu/Fe20Ni80 soft‐magnetic trilayer structure is reported and thereby modulation of magnetic parameters including damping and effective field is determined by means of the angular dependence of broadband ferromagnetic resonance measurements. At distinct precession of individual magnetic layer, spin‐pumping is found to be prevalent with expected linewidth increase. Mutual precession for wide range of resonance configuration reveals a collective reduction in anisotropy field of around 200 mT for both Fe50Pt50 and Fe20Ni80 systems. Subsequent observation of no‐excess interface damping shows the possible control of spin‐pumping effect by tuning the net flow of spin‐current in a multilayer structure. These experimental findings have significance for microwave devices that require tunable anisotropy field in magnetic multilayers

Room temperature charge-to-spin conversion from q-2DEG at SrTiO3-based interfaces

Interfacial two-dimensional electron gas (2DEG), especially the SrTiO3-based ones at the unexpected interface of insulators, have emerged to be a promising candidate for efficient charge-spin current interconversion. In this article, to gain insight into the mechanism of the charge-spin current interconversion at the oxide-based 2DEG, we focused on conducting interfaces between insulating SrTiO3 and two types of aluminium-based amorphous insulators, namely SrTiO3/AlN and SrTiO3/Al2O3, and estimated their charge-spin conversion efficiency, {\theta}_cs. The two types of amorphous insulators were selected to explicitly probe the overlooked contribution of oxygen vacancy to the {\theta}_cs. We proposed a mechanism to explain results of spin-torque ferromagnetic resonance (ST-FMR) measurements and developed an analysis protocol to reliably estimate the {\theta}_cs of the oxide based 2DEG. The resultant {\theta}_cs/t, where t is the thickness of the 2DEG, were estimated to be 0.244 nm-1 and 0.101 nm-1 for the SrTiO3/AlN and SrTiO3/Al2O3, respectively, and they are strikingly comparable to their crystalline counterparts. Furthermore, we also observe a large direct current modulation of resonance linewidth in SrTiO3/AlN samples, confirming its high {\theta}_cs and attesting an oxygen-vacancy-enabled charge-spin conversion. Our findings emphasize the defects' contribution to the charge-spin interconversion, especially in the oxide-based low dimensional systems, and provide a way to create and enhance charge-spin interconversion via defect engineering

Disentanglement of intrinsic and extrinsic side-jump scattering induced spin Hall effect in N-implanted Pt

The rapidly evolving utilization of spin Hall effect (SHE) arising from spin-orbit coupling in 5d transition metals and alloys have made giant strides in the development of designing low-power, robust and non-volatile magnetic memory. Recent studies, on incorporating non-metallic lighter elements such as oxygen, nitrogen and sulfur into 5d transition metals, have shown an enhancement in damping-like torque efficiency {\theta}_DL due to the modified SHE, but the mechanism behind this enhancement is not clear. In this paper, we study {\theta}_DL at different temperatures (100-293 K) to disentangle the intrinsic and extrinsic side-jump scattering induced spin Hall effect in N-implanted Pt. We observe a crossover of intrinsic to extrinsic side-jump mechanism as the implantation dose increases from 2*10^16 ions/cm2 to 1*10^17 ions/cm2. A sudden decrease in the intrinsic spin Hall conductivity is counterbalanced by the increase in the side-jump induced SHE efficiency. These results conclude that studying {\theta}_DL as a function of implantation dose, and also as a function of temperature, is important to understand the physical mechanism contributing to SHE, which has so far been unexplored in incorporating non-metallic element in 5d transition metals

Dense plasma irradiated platinum with improved spin Hall effect

The impurity incorporation in host high-spin orbit coupling materials like platinum has shown improved charge-to-spin conversion by modifying the up-spin and down-spin electron trajectories by bending or skewing them in opposite directions. This enables efficient generation, manipulation, and transport of spin currents. In this study, we irradiate the platinum with non-focus dense plasma to incorporate the oxygen ion species. We systematically analyze the spin Hall angle of the oxygen plasma irradiated Pt films using spin torque ferromagnetic resonance. Our results demonstrate a 2.4 times enhancement in the spin Hall effect after plasma treatment of Pt as compared to pristine Pt. This improvement is attributed to the introduction of disorder and defects in the Pt lattice, which enhances the spin-orbit coupling and leads to more efficient charge-to-spin conversion without breaking the spin-orbit torque symmetries. Our findings offer a new method of dense plasma-based modification of material for the development of advanced spintronic devices based on Pt and other heavy metals

Nonstoichiometric FePt Nanoclusters for Heated Dot Magnetic Recording Media

Heated dot magnetic recording (HDMR) provides a path to increase the areal density of magnetic recording media beyond 4 Tb/in2. HDMR-based recording media requires ultrasmall, noninteracting, and thermally stable magnetic dots with high perpendicular anisotropy. We have synthesized nonstoichiometric Fe60Pt40 nanoclusters with and without a Pt buffer layer on silicon substrates, which shows a reduction in chemical ordering temperatures. The Fe60Pt40 nanoclusters retain the hard magnetic phase up to 1023 K with the coercive field of 1.3 Tesla due to the Pt element compensation from the buffer layer. This compensation of Pt was confirmed through X-ray diffraction (XRD) investigations where two distinct phases of Fe3Pt and FePt3 are observed at elevated annealing temperatures. Micromagnetic simulations were performed to understand the effect of magnetic anisotropy, dipolar interaction, and exchange coupling between the soft magnetic Fe3Pt and hard magnetic FePt. The results imply that nonstoichiometric Fe60Pt40 with the Pt buffer layer facilitates low chemical ordering temperatures retaining the high perpendicular anisotropy with minimal noninteracting behavior, suitable for HDMR

Role of Experiential Trust in E-Shopping Behaviour: An Emerging Market Perspective

Addressing the limited research on online shopping trust in the emerging e-market context, this study examined how online experience affects experiential trust, attitude, perceived risk, perceived usefulness, and purchase intention. Further, experiential trust was tested as a mediator between online experience and attitude, perceived risk, and perceived usefulness. A structured questionnaire was administered to collect data from 583 respondents. The proposed hypotheses were tested through structural equation modeling using AMOS 23 and hierarchical regression analysis. The result indicates that online experience is significant in forming experiential trust. The findings also show that experiential trust plays an important role in influencing e-shoppers’ purchasing behavior. Furthermore, it has been found that online experience and experiential trust function as distinct predictors of perceived risk in online shopping behavior. This study provides new insights into online shopping behavior in emerging e-market scenarios. Practically, the findings suggest the strategic importance of generating experiential trust in the e-retailing context and indicate the utility of past online experiences

Facet controlled anisotropic magnons in Y<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> thin films

Directional specific control on the generation and propagation of magnons is essential for designing future magnon-based logic and memory devices for low power computing. The epitaxy of the ferromagnetic thin film is expected to facilitate anisotropic linewidths, which depend on the crystal cut and the orientation of the thin film. Here, we have shown the growth-induced magneto-crystalline anisotropy in 40 nm epitaxial yttrium iron garnet (YIG) thin films, which facilitate cubic and uniaxial in-plane anisotropy in the resonance field and linewidth using ferromagnetic resonance measurements. The growth-induced cubic and non-cubic anisotropy in epitaxial YIG thin films are explained using the short-range ordering of the Fe3þ cation pairs in octahedral and tetrahedral sublattices with respect to the crystal growth directions. This site-preferred directional anisotropy enables an anisotropic magnon–magnon interaction and opens an avenue to precisely control the propagation of magnonic current for spin-transfer logics using YIG-based magnonic technology

Highly dose dependent damping-like spin-orbit torque efficiency in O-implanted Pt

Damping-like torque (DLT) arising from the spin Hall effect (SHE) in heavy metals and their alloys has been widely explored for applications in spin–orbit torque MRAM, auto-oscillations, spin waves, and domain wall motion. In conventional materials, the DLT efficiency is limited by intrinsic properties, while attaining strong spin–orbit coupling and higher spin-charge interconversion, with no compromise to electric properties, is the need of the hour. In this Letter, we report more than 3.5 times increase in DLT efficiency, θDL, of modified Pt-oxide by employing a better approach of low energy 20 keV O+ ion implantation. The highest fluence of O+ implantation (1 × 1017 ions cm−2) in Pt enhanced the DLT efficiency from 0.064 to 0.230 and improved the spin transmission for a smaller trade-off in the longitudinal resistivity (ρPt to ρPt−Oxide) from 55.4 to 159.5 μΩ cm, respectively. The transverse spin Hall resistivity, ρSH, is found to be proportional to the square of the longitudinal resistivity, i.e., ρimpSH∝ρ2imp, implying that the enhanced SHE in O-implanted Pt is due to a side-jumping mechanism. Further, no break in the twofold as well as mirror symmetry of torques from the O-implanted Pt allows the use of spin-torque ferromagnetic resonance-based line shape analysis to quantify such torques

Magnetoimpedance of Epitaxial Y3Fe5O12 (001) Thin Film in Low-Frequency Regime

The atomically flat interface of the Y3Fe5O12 (YIG) thin film and the Gd3Ga5O12 (GGG) substrate plays a vital role in obtaining the magnetization dynamics of YIG below and above the anisotropy field. Here, magnetoimpedance (MI) is used to investigate the magnetization dynamics in fully epitaxial 45 nm YIG thin films grown on the GGG (001) substrates using a copper strip coil in the MHz–GHz frequency region. The resistance (R) and reactance (X), which are components of impedance (Z), allow us to probe the absorptive and dispersive components of the dynamic permeability, whereas a conventional spectrometer only measures the field derivative of the power absorbed. The distinct excitation modes arising from the resonance in the uniform and dragged magnetization states of YIG are respectively observed above and below the anisotropy field. The magnetodynamics clearly shows the visible dichotomy between two resonant fields below and above the anisotropy field and its motion as a function of the direction of the applied magnetic field. A low value of a damping factor of ∼4.7 – 6.1 × 10–4 is estimated for uniform excitation mode with an anisotropy field of 65 ± 2 Oe. Investigation of below and above anisotropy field-dependent magnetodynamics in the low-frequency mode can be useful in designing the YIG-based resonators, oscillators, filters, and magnonic devices