Experimental evidence of self-localized and propagating spin wave modes in obliquely magnetized current-driven nanocontacts

Through detailed experimental studies of the angular dependence of spin wave excitations in nanocontact-based spin-torque oscillators, we demonstrate that two distinct spin wave modes can be excited, with different frequency, threshold currents and frequency tuneability. Using analytical theory and micromagnetic simulations we identify one mode as an exchange-dominated propagating spin wave, and the other as a self-localized nonlinear spin wave bullet. Wavelet-based analysis of the simulations indicates that the apparent simultaneous excitation of both modes results from rapid mode hopping induced by the Oersted field.Comment: 5 pages, 3 figure

How Developmental Relationships Can Be Used by Organizations and Governments as Tools for National HRD Initiatives: India and Spain

The increased role of political and socio-cultural systems and their relationships with National Human Resource Development (NHRD) capability and capacity building may require scholars to investigate the role of contextual factors on formal and informal strategy planning and implementation for developmental relationships at both organizational and national levels. In this chapter, we explore existing practices for promoting developmental relationships from organizational and national perspectives, bringing together examples of formal and informal interventions in the context of an Asian and a European nation (India and Spain). Adopting ethnographic and hermeneutic methodologies, the chapter explores the meaning of existing practices for promoting developmental relationships from an NHRD perspective, identifying examples of interventions in the context of India and Spain. We conclude that developmental relationships contribute to NHRD by nurturing and developing capacity and capability building. Cross-cultural evidence justifies the presence of formal and informal policies and practices at organizational and national levels. Formal interventions in organizations of both countries have enabled capacity and capability development. Informally, customs, traditions, and rituals have nurtured and created a developmental culture that enables capacity and capability building. Last, developmental relationships at the national level have been promoted through various policies, schemes, and regulations in both countries. We discuss implications for international theory and practice based on the cross-country perspective in the chapter.2021-2

Length-weight relationship of brackish water finfish Thryssa kammalensoides Wongratana, 1983 from Chilika Lagoon, India

1308-1311The length-weight relationship (LWR) of brackish water finfish Thryssa kammalensoides Wongratana, 1983 is reported for the first time during the study. Specimens (n = 862) were caught with the help of local fisherman from Chilika lagoon, east coast of India during monsoon (September-October, 2018) and post-monsoon (November, 2018-January, 2019). The maximum total length recorded in this study is the new record for the species. The data revealed that LWR of T. kammalensoides of Chilika shows a significant LWR during monsoon (r2 = 0.872) whereas moderate (r2 = 0.470) during post-monsoon

Magnetic droplet solitons in orthogonal nano-contact spin torque oscillators

We study microwave signal generation as a function of drive current and applied perpendicular magnetic field in nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has strong easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The orthogonal NC-STOs exhibit a dramatic transition from the conventional ferromagnetic resonance-like spin wave mode to a magnetic droplet soliton mode. In particular, the field and current dependence of the droplet soliton near threshold are discussed. Near threshold the droplet soliton undergoes complex dynamics that include mode hopping, as evident in the experimental frequency domain and magnetoresistance response

Spin transfer torque generated magnetic droplet solitons (invited)

We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90°, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy

Signals in the Soil: An Introduction to Wireless Underground Communications

In this chapter, wireless underground (UG) communications are introduced. A detailed overview of WUC is given. A comprehensive review of research challenges in WUC is presented. The evolution of underground wireless is also discussed. Moreover, different component of UG communications is wireless. The WUC system architecture is explained with a detailed discussion of the anatomy of an underground mote. The examples of UG wireless communication systems are explored. Furthermore, the differences of UG wireless and over-the-air wireless are debated. Different types of wireless underground channel (e.g., In-Soil, Soil-to-Air, and Air-to-Soil) are reported as well

Electrochemically Exfoliated Layered Carbons as Sustainable Anode Materials for Lead Carbon Hybrid Ultracapacitor

Lead-carbon hybrid ultracapacitors (Pb−C HUC) have become apparent as a way out of the sulfation issue of lead-acid batteries, simultaneously enhancing the system‘s power density and cycle life. In this work, exfoliated graphene oxides (EGO) were synthesized by the electrochemical exfoliation method followed by chemical activation and carbonization at 600 °C (AEGO-600). The composite electrode delivered 800 F g−1 capacitance at 1 A g−1. The Pb−C HUC fabricated using AEGO-600 anode and PbO2 cathode can achieve capacitance of 325 F g−1 at 10 A g−1 and retain 71 % capacitance after 15000 charge-discharge cycles in the voltage range of 2.3–0.8 V. The highly stable capacitance was due to the formation of layered carbons in AEGO-600 that enhanced the favorable electrolyte ion assessment to maximum active sites. Owing to the facile, cost-effective synthesis approach and better charge storage behavior, the activated-exfoliated graphene oxides thus produced could be suitable candidates for future hybrid ultracapacitor systems. © 2022 Wiley-VCH GmbH

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