Deposition of Crystalline GdIG Samples Using Metal Organic Decomposition Method

Fabrication of high quality ferrimagnetic insulators is an essential step for ultrafast magnonics, which utilizes antiferromagnetic exchange of the ferrimagnetic materials. In this work, we deposit high-quality GdIG thin films on a (111)-oriented GGG substrate using the Metal Organic Decomposition (MOD) method, a simple and high throughput method for depositing thin film materials. We postannealed samples at various temperatures and examined the effect on structural properties such as crystallinity and surface morphology. We found a transition in the growth mode that radically changes the morphology of the film as a function of annealing temperature and obtained an optimal annealing temperature for a uniform thin film with high crystallinity. Optimized GdIG has a high potential for spin wave applications with a low damping parameter in the order of 10(-3), which persists down to cryogenic temperatures

Hazards and health problems in occupations dominated by aged workers in South Korea

Abstract Background South Korea’s population is aging more rapidly than any other country. Aging of the productive population will lead to shortage of labor and the decreasing quality of the labor force in South Korea. South Korea needs health care strategies to support the establishment of work environments that are appropriate for elderly workers who have reduced physical capacity. This paper aims to identify occupations that are dominated by aged workers and assess the exposure to hazards and work-related health problems of aged workers in these occupations. Methods We identified the 20 occupations in South Korea that employ the most aged workers (at least 55 years-old), among all 149 occupations that are defined as minor categories (identified by three digits) by the Korean Standard Classification of Occupations (KSCO). Exposure to hazards and work-related health problems of individuals in these occupations were evaluated by analyzing the results of the fourth Working Conditions Survey of 2014. Results Among the 20 occupations that employ the most aged workers, ‘Elementary Occupations’, which the KSCO classifies as major category (9), had the largest proportion of aged workers. After this, there were five occupations of skilled manual workers and six occupations of skilled non-manual workers. Aged workers in elementary and skilled manual occupations reported frequent exposure to job-specific hazards, such as noise, vibrations, high and low temperatures, solvents, and chemicals. Relative to other workers, aged workers in the occupations reported more frequent exposure to ergonomic hazards, such as tiring or painful positions, carrying or moving heavy loads, and repetitive movements, and also reported more work-related musculoskeletal disorders and general fatigue. Injury due to accident was common in machinery-handling occupations. Conclusion Job-specific hazards should be reduced to prevent occupation-related disorders in elementary and skilled manual occupations that are dominated by aged workers

Enhanced spin Seebeck effect via oxygen manipulation

Spin Seebeck effect (SSE) refers to the generation of an electric voltage transverse to a temperature gradient via a magnon current. SSE offers the potential for efficient thermoelectric devices because the transverse geometry of SSE enables to utilize waste heat from a large-area source by greatly simplifying the device structure. However, SSE suffers from a low thermoelectric conversion efficiency that must be improved for widespread application. Here we show that the SSE substantially enhances by oxidizing a ferromagnet in normal metal/ferromagnet/oxide structures. In W/CoFeB/AlOx structures, voltage-induced interfacial oxidation of CoFeB modifies the SSE, resulting in the enhancement of thermoelectric signal by an order of magnitude. We describe a mechanism for the enhancement that results from a reduced exchange interaction of the oxidized region of ferromagnet, which in turn increases a temperature difference between magnons in the ferromagnet and electrons in the normal metal and/or a gradient of magnon chemical potential in the ferromagnet. Our result will invigorate research for thermoelectric conversion by suggesting a promising way of improving the SSE efficiency.ISSN:2041-172

Spin Hall magnetoresistance and the effect of post-annealing temperature in the MOD-grown HoIG

We present the fabrication of ultrathin Ho3Fe5O12 (HoIG) films on 111- oriented-Gd3Ga5O12 (GGG) via the metal-organic decomposition (MOD) method followed by a sequence annealing process. We characterized the crystal structure, surface morphology, and magnetic properties to study the effect of annealing temperature on the quality of MOD-grown HoIG films. For temperatures higher than 800 ⁰C, we observe the infiltration of Iron (Fe) from the HoIG film into the GGG substrate. In particular, the Fe-diffusion is significantly enhanced for a 1000 ⁰C-annealed sample of which crystal structure and magnetic properties are also affected. For temperatures lower than 800 ⁰C, on the other hand, the smooth surface and strong crystallinity cannot be guaranteed. This suggests that an annealing temperature of 800 ⁰C is the optimal condition for the MOD-grown HoIG film. The quality of the sample is further confirmed by measuring the spin Hall magnetoresistance (SMR) of HoIG/Pt, in which we found the unconventional angular dependence and comparable spin mixing conductance similar to the previous reports in other single crystalline IGs. © 2023 Elsevier B.V.11Nsciescopu

Field-free spin-orbit torque switching of GdCo ferrimagnet with broken lateral symmetry by He ion irradiation

Current-induced magnetization switching by spin-orbit torque (SOT) is of great importance for the energy-efficient operation of spin-based memory and logic devices. However, the requirement of an external in-plane magnetic field to deterministically switch the perpendicular magnetization of a device is a bottleneck for device application. There have been many efforts to realize field-free SOT switching using interlayer/exchange coupling, the spin valve structure, or materials with lateral symmetry breaking. However, limitations of material selection or layer structure modification hinder the application of these methods in practice. Here, we demonstrate the field-free SOT switching of a GdCo ferrimagnet with lateral symmetry breaking by He ion irradiation. Local control of the magnetic property with different He ion irradiation conditions induces a lateral magnetic gradient orthogonal to the current flow direction in the ferrimagnet. We also observe out-of-plane-SOT generation due to lateral symmetry breaking, which is essential for field-free switching. Since the He ion irradiation technique is utilized for the fabrication of complementary−metal−oxide−semiconductors, and resolution can reach the nanometer level, our findings have the potential to serve as the basis for new developments in the fabrication of wafer-scale spintronic memory and logic devices with high energy efficiency and high density. © 2023 Acta Materialia Inc.FALS

Efficient conversion of orbital Hall current to spin current for spin-orbit torque switching

Spin Hall effect, an electric generation of spin current, allows for efficient control of magnetization. Recent theory revealed that orbital Hall effect creates orbital current, which can be much larger than spin Hall-induced spin current. However, orbital current cannot directly exert a torque on a ferromagnet, requiring a conversion process from orbital current to spin current. Here, we report two effective methods of the conversion through spin-orbit coupling engineering, which allows us to unambiguously demonstrate orbital-current-induced spin torque, or orbital Hall torque. We find that orbital Hall torque is greatly enhanced by introducing either a rare-earth ferromagnet Gd or a Pt interfacial layer with strong spin-orbit coupling in Cr/ferromagnet structures, indicating that the orbital current generated in Cr is efficiently converted into spin current in the Gd or Pt layer. Furthermore, we show that the orbital Hall torque can facilitate the reduction of switching current of perpendicular magnetization in spin-orbit-torque-based spintronic devices.Comment: 19 pages, 3 figure