Altermagnets

by Hansraj Agrawal | Jul 14, 2025 | Science

Researchers have discovered a rare and useful behaviour in a new class of magnetic materials called altemagnets, specifically in a compound named chromium antimonide (CrSb).

Altermagnets are magnetic materials whose surface (outside) display no magnetic properties — they won’t stick to a fridge. But the ‘insides’ have magnetic properties.

Altermagnets combine the best features of ferromagnets (like fridge magnets) and antiferromagnets (which cancel out their own magnetism). Although they show no external magnetism, their internal electron behaviour can be highly useful for advanced technologies like spintronics, which use electron spin rather than charge.

CrSb stands out for its strong magnetic order, which lasts well above room temperature, and a giant “spin-splitting” effect — over 30 times that of room temperature — making it a top candidate for practical applications.

Now, scientists at the SN Bose National Centre for Basic Sciences (SNBNCBS) have discovered a new property in CrSb called direction-dependent conduction polarity (DDCP). When current flows along the layers of the crystal, electrons carry it (n-type behaviour). But across the layers, the current is carried by holes (p-type behaviour). This switch, depending on direction, is extremely rare and challenges the conventional p-type/n-type classification of materials.

CrSb is the first altermagnet known to show this dual nature. It could allow future devices — like solar cells or thermoelectrics — to function without combining different materials or doping, making them simpler, smaller, and more efficient. Made from abundant, non-toxic elements, CrSb is also environmentally friendly. “It holds great promise for the next generation of electronic and spintronic devices,” says a press release.

Phase-changing emulsion

Researchers at the Fraunhofer Institute, Germany, have developed emulsions made of phase-changing materials (PCMs) and water, or mixtures of water and glycol for applications such as air conditioning inside buildings and cooling industrial machinery.

PCM emulsions are a mix of paraffins and water, or water-glycol, and are used primarily in the mobility sector, where the addition of glycol keeps the mixture from freezing.

The researchers used paraffins, which are dispersed or emulsified in water, or the water-glycol mixtures. Surfactants stabilise the ultrafine paraffin droplets distributed throughout the water, which lends the mixture thermal and mechanical stability.

The emulsions use the high energy density of paraffins during the phase transition from solid to liquid. Because the paraffins are emulsified in water, they can remain liquid regardless of their phase state in the emulsion that is created and can be used as heat transfer liquids in heating and cooling networks — meaning that the mixtures can be pumped through pipes. During the phase change, the PCMs absorb or release large amounts of heat even as their temperature remains constant. This allows for achieving twice the storage density of water — which is currently used as a heat carrier in conventional heating and cooling supply networks — in the PCM melting range while keeping the volume the same.

In addition to their high storage density, PCM emulsions also have a number of other advantages. Owing to the high heat storage capability of PCMs, systems that use them can be designed to take up less space.

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Published on July 14, 2025

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Time to roll out solar-roofed vehicles

by Hansraj Agrawal | Jul 14, 2025 | Science

RE BOOST. An e-truck with a solar hood and photovoltaic roof, developed by Fraunhofer Institute of Germany

Between August 25 and 31, an interesting car race is set to take place in Australia. The racing cars will be flagged off at Adelaide in the south and they will zip 3,000 km across the country and pull up at Port Darwin in the north.

What’s interesting here is that the racing cars are solar-powered. And the race is set in peak Australian winter, under limited sunshine.

The annual Bridgestone World Solar Challenge has been around for several years, but will now see an Indian participation for the first time. A group of students from the Centre for Innovation, IIT-Madras, will race their solar-powered ‘Aagneya’ car.

The objective of the challenge is to promote solar in vehicles, but, clearly, there may never be a time when regular passenger cars are fully solar-powered — there just isn’t enough power. However, with electric vehicles growing in popularity, many have wondered about the feasibility of having a solar panel on the vehicle’s roof to generate some electricity, even if only a little, to give the batteries an extra oomph.

But technology is moving ahead of that. Today, vehicle companies are not looking at solar panels bolted to the roof; instead, the entire roof will be a solar panel. This is ‘vehicle integrated photovoltaics’ or VIPV — solar cells are directly embedded unobtrusively into surfaces like the roof, hood and side panels of the vehicle. The entire skin of the vehicle becomes a solar power generator.

“This is an emerging technology,” says Prof Y Raja Sekhar of Vellore Institute of Technology, who is one of the four authors of a study on VIPV in India, published in Energy. The study was conducted by VIT, University of Lisbon (Portugal), and Fitchner Consulting Engineers.

They ran a VIPV car for three hours, measured the generation, and concluded that it is possible to get 1,200-1,800 Whr “when driven a full day”.

Sekhar told Quantum that solar power can potentially take care of auxiliary power consumption — such as lighting and AC — reducing the load on batteries. The VIPV power can indeed charge the batteries, but that would call for some extra instrumentation, with the corresponding disadvantage of increased weight.

Work is happening globally in this area. For example, Fraunhofer Institute of Germany developed a 115 W solar hood, and a 3.2 kW PV roof on an 18-tonne e-truck. Companies like Sono Motors, Lightyear, Toyota and Mercedes are developing prototype VIPV cars.

Mercedes announced in December 2024 the invention of a solar paint “that could be seamlessly applied to the bodywork of EVs”. It said that the active photovoltaic surface can, under ideal conditions, give an extra 12,000 km a year.

“This could be a highly effective solution for increased electric range and fewer charging stops,” Mercedes said.

Challenges

VIPV is an evolving technology and there are challenges. The study points to one — a “significant drop in PV efficiency due to high module temperatures”. The authors suggest further research into active and passive module cooling techniques, perhaps with the use of phase-changing chemicals.

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Published on July 14, 2025

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The XX-factor

by Hansraj Agrawal | Jun 29, 2025 | Science

The XX-factor

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Space agency ISRO urgently needs to tackle ground realities

by Hansraj Agrawal | Jun 29, 2025 | Science

As Shubhanshu Shukla becomes the second Indian to hurtle into space, ferried by SpaceX’s Falcon 9 rocket, the country erupts in joy. However, this happy occasion is also a moment of reckoning for the national space agency ISRO.

So far this year, two of the seven strategic space missions launched from the rocket port in Sriharikota, Andhra Pradesh, failed — a concerning 29 per cent failure rate.

Worse is the shortfall in the targeted space missions — only seven were accomplished of the planned 30 between the last quarter of FY24 and FY25.

This implies a mere 23 per cent success rate, as indicated by data from ISRO and the Indian National Space Promotion and Authorisation Centre (IN-SPACe), the regulator for private sector space companies.

In February 2024, the country’s ‘integrated launch manifesto’ was announced, with plans for 30 space launches — commercial and non-commercial — by the government and private players, including seven test launches connected with India’s human space flight mission Gaganyaan.

But the actual achievement pales in comparison with the global competition.

Elon Musk-owned US company SpaceX, through its Falcon rockets, carried out 134 orbital launches in 2024 and 78 in 2025.

Missed milestones

IN-SPACe said that of the 14 commercial missions identified, seven are by NewSpace India Limited (NSIL), including the production of two polar satellite launch vehicles (PSLV) through an industry consortium.

“This marks a substantial increase in launch activity compared to previous years, and is a positive indicator of the expanding space ecosystem in the country,” IN-SPACe had said in the launch manifesto.

However, the actual numbers are nowhere near the target. On an average, ISRO carries out about six space launches a year; so the 30 space missions outlined by IN-SPACe appear ambitious.

During the period under review (Q4 of FY24 and FY25), only the following missions were carried out by ISRO: PSLV-C58 on January 1, 2024; GSLV-F14 on February 17; SSLV-D3 on August 16; PSLV-C59 on December 5; PSLV-C60 on December 30; GSLV-F15 on January 29, 2025; and PSLV-C61 on May 18.

A disappointing year

Both the missions in 2025 failed.

On May 18, a PSLV rocket carrying an earth observation satellite (EOS-09) with synthetic aperture radar (SAR), designed to strengthen surveillance capabilities, failed during flight. The EOS-09 satellite, with a lifespan of five years, was similar in function to the EOS-04 launched in 2022.

On January 29, the NVS-02 navigation satellite failed to reach its intended orbit due to a pyro valve malfunction. The satellite was carried by another expendable rocket, GSLV-F15. The valve failed to open, preventing oxidiser flow, despite the fuel pumps functioning.

A retired senior ISRO official suggested that the PSLV-C61 third-stage issue could stem from a faulty valve or electrical connector, leading to the pressure drop.

The back-to-back failures are unsettling.

The NVS-02 navigation satellite was meant to replace the ageing IRNSS-1E satellite, as part of India’s regional navigation system.

The cost of two failed missions, coupled with their replacement cost and the opportunity cost, would run into several hundreds of crores of rupees.

Launches to come

Looking ahead, the first PSLV rocket made by the HAL-L&T consortium is expected to lift off later this year.

Similarly, the much-delayed NISAR (NASA-ISRO synthetic aperture radar) satellite, a joint initiative of India and the US, is slated to be carried by the GSLV-F16 rocket sometime in July.

While a couple of start-ups have orbited satellites made by them, the two private rocket makers have come out with their full-fledged rockets.

It is time for ISRO to momentarily lower its gaze, away from the skies and towards the earth below, to gain a grip on the ground realities and set right its course.

If the Indian space sector continues to move at the current pace, the targeted $44-billion space economy by 2033 will remain a distant dream.

(The writer is an independent journalist based in Chennai)

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Published on June 29, 2025

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Small-scale heliostat

by Hansraj Agrawal | Jun 29, 2025 | Science

Scientists Adithyan TR, Prof Sreeram K Kalpathy and Prof Tiju Thomas of the Department of Metallurgical and Materials Engineering, Indian Institute of Technology (IIT), Madras, have designed and evaluated a tilt-roll two-axis tracking heliostat (solar concentrator) that is economically viable for small-scale applications.

In this heliostat, the design eliminates the need for a commercially available solar tracking system, so it can be deployed in areas with limited installation space. The solar positioning system is capable of operating independently, without the need for a powerful microcontroller or microprocessor.

“The combination of the tilt-roll dual-axis tracking system achieves a heliostat design that could be easily deployed for small-scale usage and experimental purposes in households and academia,” says an article in IIT-M Tech-Talk.

“The results have been demonstrated on a rooftop at IIT-Madras. The heliostat prototype could reflect the sun’s radiation to the desired target. The dual-axis heliostat design used here provides an effective way to track the sun’s movement for maximum solar energy capture by combining tilt and roll mechanisms,” the article says.

Future work will focus on developing and testing advanced heliostat drive devices, such as heliostat with induction motors, and linear drives to reduce operation power losses. Future work may also focus on making the system robust under dynamic wind-loading conditions.

Dr Ajay Chandak, an innovator, developer and entrepreneur in sustainability and a global advisor of Solar Cookers International (SCI), says in the article that the use of heliostats for power generation is obsolete due to the low cost of solar PV.

However, such smaller heliostats can be useful in solar thermal applications.

Solar-to-hydrogen energy

Scientists at the Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru, have developed a next-generation device that produces green hydrogen by splitting water molecules using only solar energy and earth-abundant materials, without relying on fossil fuels or other expensive resources.

The team designed a silicon-based photoanode using an innovative n-i-p heterojunction architecture, consisting of stacked n-type titanium dioxide, intrinsic (undoped) silicon and p-type nickel oxide semiconductor layers, which work together to enhance charge separation and transport efficiency. The materials were deposited using magnetron sputtering, a scalable and industry-ready technique that ensures precision and efficiency. This engineering approach allowed better light absorption, faster charge transport and reduced recombination loss — key ingredients for efficient solar-to-hydrogen conversion.

“The device is highly effective at generating hydrogen under solar energy,” says a press release. It also showcases “exceptional long-term stability, operating continuously for over 10 hours in alkaline conditions with only a 4 per cent performance drop, a rare feat in Si-based photoelectrochemical systems,” the release says.

This new device is attractive for several reasons, including high efficiency, low energy input, robust durability and cost-effective materials, all in one package. It even demonstrated successful performance at a large scale, with a 25 sq cm photoanode delivering excellent solar water-splitting results.

“By selecting smart materials and combining them into a heterostructure, we have created a device that not only boosts performance but can also be produced on a large scale,” says Dr Ashutosh Singh, who led the research. “This brings us one step closer to affordable, largescale solar-to-hydrogen energy systems,” Singh says in the release.