Solar Energy
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!
DGIST enhances quantum dot solar cell performance
by Riko Seibo
Tokyo, Japan (SPX) Oct 04, 2024
A research team led by Professor Jongmin Choi from the Department of Energy Science and Engineering at DGIST, in collaboration with Gyeongsang National University’s Professor Tae Kyung Lee and Kookmin University’s Professor Younghoon Kim, has developed a new method that significantly boosts the performance and longevity of perovskite quantum dot solar cells. Their innovative approach addresses a key issue: surface distortions on quantum dots that hinder solar cell efficiency.
Perovskite quantum dots are widely regarded as essential for next-generation solar cells due to their high light-to-electricity conversion efficiency and scalability. However, the process of replacing the “ligands” on their surface often causes distortions, akin to crumpled paper, that degrade solar cell performance.
The research team tackled this problem by introducing short ligands that firmly grip both sides of the quantum dots. This method effectively restores the quantum dot’s distorted surface, resembling the process of flattening crumpled paper. By smoothing the surface, they significantly reduced defects and improved both the performance and the stability of the solar cells. The power conversion efficiency rose from 13.6% to 15.3%, and the cells maintained 83% of their performance over 15 days, marking a major advancement in solar cell technology.
“Through this research, we could minimize surface defects on the quantum dots and stabilize their surfaces by newly adopting these amphiphilic ligands, thereby significantly improving the efficiency and stability of the solar cells,” explained Professor Jongmin Choi. He also noted the team’s intention to extend this approach to other photoelectric devices in the future.
This study, a collaborative effort by DGIST, Gyeongsang National University, and Kookmin University, was supported by the National Research Council of Science and Technology, the DGIST R and D Program, and the New Faculty Research Foundation at Gyeongsang National University. The findings were published in the ‘Chemical Engineering Journal’ on September 15, 2024.
Research Report:Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots
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Philippines’ Marcos opens first EV battery plant
by AFP Staff Writers
Manila (AFP) Sept 30, 2024
President Ferdinand Marcos inaugurated on Monday the first factory for electric vehicle batteries in the Philippines, calling it the “future” of clean energy.
The Australian-owned lithium-iron-phosphate factory aims to produce two gigawatt-hours of batteries per year by 2030, powering about 18,000 electric vehicles or nearly half a million home battery systems.
“We have worked very hard and tried to do our best to bring this kind of technology to the Philippines with a clear recognition that this is the future,” Marcos said in a livestreamed speech.
“As the first manufacturing plant in the Philippines for advanced iron phosphate batteries… (it) sets the stage for the Philippines to become a player in clean energy storage in our part of the world.”
Located in New Clark city north of Manila, the StB Giga Factory Inc. facility will create 2,500 local jobs and channel five billion pesos ($89.2 million) into the economy each year, Marcos said.
The investment aligns with the government’s efforts to “transition our country to renewable energy”, and would help Manila “entice more investors in renewable energy facilities in the country”, he added.
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Fire breaks out at Chinese battery giant CATL plant
by AFP Staff Writers
Beijing (AFP) Sept 29, 2024
A fire broke out Sunday at a factory belonging to Chinese battery giant CATL, which supplies electric vehicle makers including Tesla, but only a “relatively small” impact on operations is expected, the company said.
A CATL spokesperson said no injuries or casualties had occurred at the plant in the coastal city of Ningde, and that “the reasons behind this accident are still under investigation”.
Emergency services were sent to the plant to fight the fire and to organise the evacuation of any people who were inside the 15,000 square metre (160,000 square feet) site, a statement by the Dongqiao Economic and Technological Development Zone said.
Firefighters were alerted to the blaze just before 11:30 AM local time (0330 GMT).
It was not immediately clear what was produced at the plant, CATL’s base in the eastern province of Fujian, but the company said the effect of the now extinguished fire would not be significant.
“The impact to CATL’s overall production operation is relatively small,” the spokesperson said.
Videos published by the Chinese business media outlet Cailianshe, and posted on the Weibo social network, showed parts of a large white building in flames with thick gray smoke rising into the air.
AFP could not immediately verify the authenticity of the images.
CATL was founded in 2011 and produces more than a third of the electric vehicle batteries sold worldwide for automakers that include Mercedes-Benz, BMW, Volkswagen, Toyota, Honda and Hyundai.
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