Solar Energy

Unusual magnetic transition in perovskite oxide can help boost spintronics

Published

4 years ago

March 30, 2021

sarosh

Unusual magnetic transition in perovskite oxide can help boost spintronics

Transition metal perovskites oxides exhibit several desirable properties, including high-temperature superconductivity and electrocatalysis. Now, scientists at Tokyo Institute of Technology explore the structure and properties of a perovskite oxide, PbFeO3, in anticipation of the unusual charge distribution and exotic magnetic transitions displayed by such systems. They report two of the magnetic transitions, with a distinctive transition above room temperature and look into its causes, opening doors to potential applications in realizing new spintronic devices.

The advent of electronics has revolutionized our lives to an extent where it is impossible to imagine going about our day without relying on an electronic device in some form. What is even more remarkable, however, is that we can improve these devices even further by harnessing the electron’s “spin” – a property which makes the electron behave like a magnet – to create memory devices that are faster and use lower power than traditional electronics.

Accordingly, the field devoted to this endeavor, aptly called “spintronics”, relies on exploiting the “spin state” of the electron. However, controlling spin can be extremely tricky, a fact that often leads scientists on a hunt for materials with ordered spin states.

Their attention has recently turned to lead-based transition metal perovskite oxides, a class of materials represented by PbMO3 (where the “M” indicates 3d transition metal ion), that display rather interesting phase transitions in spin states, making them appealing for practical applications.

In a recent study published in Nature Communications, a team of scientists from China, Japan, Taiwan, Switzerland, Germany, France, and USA, examined the perovskite oxide PbFeO3, a compound that has evaded inspection until now, owing to difficulties in synthesizing samples and resolving its crystal structure.

“”The perovskite family of PbMO3 exhibits complex charge distributions and RFeO3 (R = rare earth) shows several interesting spin-related properties, such as laser-induced ultrafast spin reorientation, so we expect similarly characteristic charge distribution and rich spin-state transitions for PbFeO3,” comment Prof. Masaki Azuma from Tokyo Institute of Technology, Japan and Prof. Youwen Long from Chinese Academy of Science, who led the study.

Consequently, the team investigated the structure, charge state, and magnetic properties of PbFeO3 using a variety of characterization techniques and backed up their observation with density functional theory (DFT) calculations.

The team found that PbFeO3 crystallized into a unique “charge-ordered” state in which a layer of Pb2+ ions was interleaved by two layers made up of a mixture of Pb2+ and Pb4+ ions in a 3:1 ratio, along the direction of layer stacking (Figure 1).

On cooling the sample from high temperature, the team observed two distinct magnetic phase transitions: a weak ferromagnetic transition occurring at 600 K (327C) characterized by a “canted antiferromagnetic” spin ordering (oppositely directed neighboring spins), and a continuous spin reorientation (SR) transition at 418 K (145C) (Figure 2).

The SR transition, although common in all RFeO3 perovskites, stood out in this case because it occurred at a much higher temperature compared to those for other perovskites, and unlike the R – Fe magnetic interactions usually identified as the cause for this transition, there was no such counterpart in the case of PbFeO3.

To resolve the conundrum, scientists turned to DFT calculations, which revealed that the unique charge ordering in PbFeO3 led to the formation of two Fe3+ “sublattices” with competing energies that, in turn, caused the peculiar SR transition.

The team is thrilled by these findings and their implications for future applications. “”Our work provides a new avenue for studying the charge ordering phase and distinctive SR transition with potential applications in spintronic devices due to the high transition temperature and possible tuning,” remarks the theoretical team leader, Prof. Hena Das.

One thing’s for sure – we’re one step closer to making spintronics the reality of tomorrow!

Source link

Solar Energy

Battery boom drives Bangladesh lead poisoning epidemic

Published

19 hours ago

April 1, 2025

sarosh

Battery boom drives Bangladesh lead poisoning epidemic

By Philippe ALFROY

Mirzapur, Bangladesh (AFP) April 1, 2025

Bangladeshi Junayed Akter is 12 years old but the toxic lead coursing through his veins has left him with the diminutive stature of someone several years younger.

Akter is one of 35 million children — around 60 percent of all children in the South Asian nation — who have dangerously high levels of lead exposure.

The causes are varied, but his mother blames his maladies on a since-shuttered factory that hastily scrapped and recycled old vehicle batteries for profit, in the process poisoning the air and the earth of his small village.

“It would start at night, and the whole area would be filled with smoke. You could smell this particular odour when you breathed,” Bithi Akter told AFP.

“The fruit no longer grew during the season. One day, we even found two dead cows at my aunt’s house.”

Medical tests showed Junayed’s blood had twice the level of lead deemed by the World Health Organization to cause serious, and likely irreversible, mental impairment in young children.

“From the second grade onward, he didn’t want to listen to us anymore, he didn’t want to go to school,” Bithi said, as her son sat next to her while gazing blankly out at the courtyard of their home.

“He cried all the time too.”

Lead poisoning is not a new phenomenon in Bangladesh, and the causes are manifold.

They include the heavy metal’s widespread and continued use in paint, in defiance of a government ban, and its use as an adulterant in turmeric spice powder to improve its colour and perceived quality.

A great many cases are blamed on informal battery recycling factories that have proliferated around the country in response to rising demand.

Children exposed to dangerous levels of lead risk decreased intelligence and cognitive performance, anaemia, stunted growth and lifelong neurological disorders.

The factory in the Akter family’s village closed after sustained complaints from the community.

But environmental watchdog Pure Earth believes there could be 265 such sites elsewhere in the country.

“They break down old batteries, remove the lead and melt it down to make new ones,” Pure Earth’s Mitali Das told AFP.

“They do all this in the open air,” she added. “The toxic fumes and acidic water produced during the operation pollute the air, soil and water.”

– ‘They’ve killed our village’ –

In Fulbaria, a village that sits a few hours’ drive north of the capital Dhaka, operations at another battery recycling factory owned by a Chinese company are in full swing.

On one side are verdant paddy fields. On the other, a pipe spews murky water into a brackish pool bordered by dead lands, caked with thick orange mud.

“As a child, I used to bring food to my father when he was in the fields. The landscape was magnificent, green, the water was clear,” engineer and local resident Rakib Hasan, 34, told AFP.

“You see what it looks like now. It’s dead, forever,” he added. “They’ve killed our village.”

Hasan complained about the factory’s pollution, prompting a judge to declare it illegal and order the power be shut off — a decision later reversed by the country’s supreme court.

“The factory bought off the local authorities,” Hasan said. “Our country is poor, many people are corrupt.”

Neither the company nor the Chinese embassy in Dhaka responded to AFP’s requests for comment on the factory’s operations.

Syeda Rizwana Hasan, who helms Bangladesh’s environment ministry, declined to comment on the case because it was still before the courts.

“We regularly conduct operations against the illegal production and recycling of electric batteries,” she said.

“But these efforts are often insufficient given the scale of the phenomenon.”

– ‘Unaware of the dangers’ –

Informal battery recycling is a booming business in Bangladesh.

It is driven largely by the mass electrification of rickshaws — a formerly pedal-powered means of conveyance popular in both big cities and rural towns.

More than four million rickshaws are found on Bangladeshi roads and authorities estimate the market for fitting them all with electric motors and batteries at around $870 million.

“It’s the downside of going all-electric,” said Maya Vandenant of the UN children’s agency, which is pushing a strategy to clean up the industry with tighter regulations and tax incentives.

“Most people are unaware of the dangers,” she said, adding that the public health impacts are forecast to be a 6.9 percent dent to the national economy.

Muhammad Anwar Sadat of Bangladesh’s health ministry warned that the country could not afford to ignore the scale of the problem.

“If we do nothing,” he told AFP, “the number of people affected will multiply three or fourfold in the next two years.”

Source link

Solar Energy

Modi to kick off construction of India-Sri Lanka solar plant

Published

3 days ago

March 30, 2025

sarosh

Modi to kick off construction of India-Sri Lanka solar plant

by AFP Staff Writers

New Delhi (AFP) Mar 28, 2025

Indian Prime Minister Narendra Modi will launch the construction of a long-delayed solar power project during his upcoming visit to Sri Lanka, an official said on Friday.

Vikram Misri, the secretary of India’s foreign ministry, said Modi and Sri Lankan President Anura Kumara Dissanayake will witness a virtual groundbreaking ceremony for their joint-venture solar power project in the island’s northeast on April 5.

The proposed 120-megawatt venture in the northeastern coastal district of Trincomalee has stalled for years, but New Delhi backed it as a joint project between the neighbouring nations.

“This, in many senses, is going to be a milestone in the bilateral partnership,” Misri told reporters in New Delhi.

“They will together dedicate several projects that are being built with Indian assistance in Sri Lanka and will also witness the exchange of several MoUs pertaining to energy connectivity, digitisation, defence, health, and multisectoral grant assistance.”

The pair will watch the virtual groundbreaking from Sri Lankan capital Colombo. The costs of the project were not immediately available.

The groundbreaking, a day before Modi concludes his two-night visit to Sri Lanka, comes as Colombo grapples with the competing interests of its powerful northern neighbour and China, its largest lender.

Modi will be the first foreign head of government to visit the island nation under the new administration of leftist Dissanayake. He flies into Colombo on April 4 after attending a regional conference in Thailand.

Dissanayake’s first foreign visit after his election last year was to New Delhi in December.

Sri Lankan officials in Colombo said Modi and Dissanayake will travel to the northern Buddhist pilgrimage city of Anuradhapura on April 6.

Dissanayake travelled to Beijing in January, underscoring Sri Lanka’s delicate balancing act in maintaining ties with the two regional rivals.

New Delhi has been concerned about China’s growing influence in Sri Lanka, which it considers to be within its sphere of geopolitical influence.

Source link

Solar Energy

Optical advances offer boost to next-generation solar module designs

Published

3 days ago

March 30, 2025

sarosh

Optical advances offer boost to next-generation solar module designs

by Robert Schreiber

Berlin, Germany (SPX) Mar 30, 2025

In 2023, solar photovoltaic (PV) systems accounted for over 5 percent of global electricity output, with installed capacity doubling roughly every two to three years. Optical technologies are now emerging as key enablers to further enhance module efficiency and enable new applications, including aesthetically tailored solar panels for building facades. A new expert-driven report, coordinated by Helmholtz-Zentrum Berlin (HZB) scientists Prof. Christiane Becker and Dr. Klaus Jager, offers a detailed analysis of the most promising innovations in this area.

Solar photovoltaics have become one of the most affordable sources of electricity worldwide. As of November 2024, global PV installations surpassed two terawatts, underscoring the rapid pace of expansion and cost decline.

Contributions from 22 leading research institutions

“At a recent workshop, we discussed how the optics community can contribute to the further growth of photovoltaics,” said Prof. Christiane Becker, who leads the Solar Energy Optics Department at HZB. Along with Dr. Klaus Jager, she brought together a team of 27 experts from 22 institutions across nine countries to produce a wide-ranging review of emerging PV and optical technologies.

Breakthrough optical concepts

Beginning with a comprehensive look at current terawatt-scale PV deployment, the report identifies critical areas where optical strategies can make significant contributions. “We have also identified a number of optical concepts that are currently only on the threshold of economic viability, but which hold the most promise for advancing PV technology,” said Becker. Key areas include multi-junction solar cells, which offer the highest efficiencies among all PV technologies and could help reduce the levelized cost of energy.

Sustainability and aesthetics

The review also emphasizes the importance of environmentally responsible manufacturing and the reduced use of scarce materials through eco-design approaches. Another highlighted innovation is the development of colored PV modules suitable for integration into building architecture. “Especially in cities, we need to use facades and other surfaces too for solar energy conversion, and of course, it does matter how the PV modules look. Such innovative solar modules allow sophisticated aesthetic solutions,” said Becker.

Becker and Jager believe the review will serve not only as a valuable resource for researchers but also for funding bodies and policy strategists seeking to accelerate the deployment of advanced solar technologies.

Research Report:Optics for Terawatt-Scale Photovoltaics: Review and Perspectives