. 24/7 Space News .
Physicists find peculiarities in a material with a giant magnetocaloric effect
by Staff Writers
Moscow, Russia (SPX) Aug 29, 2016

This picture illustrates the magnetocaloric effect. Image courtesy Mirsad Todorovac. For a larger version of this image please go here.

The magnetocaloric effect (MCE) is manifested in cooling or heating of the magnetic material (a material having magnetic properties) in an external magnetic field. This phenomenon was first discovered in the 19th century, but the first theoretical justification was obtained some 40 years later. During the last decades MCE has been thoroughly studied, and in recent years one can observe a real boom of the reports devoted to this phenomenon.

This is due to, first of all, the fact that the measurement of the MCE is used as a method of study of the magnetic phase transitions in different materials - the MCE data is used to refine the phase diagrams of magnetic materials. Secondly, the MCE disposes a fairly extensive area of possible applications: magnetocaloric materials have been successfully used to produce ultra-low temperatures, and also have good prospects in the heat engines' and refrigeration units' production.

In the course of the study the scientists found that the slightest dislocation in the crystal structure of FeRh alloys has a significant impact on the manifestation of MCE.

According to one of the authors, Radel Gimaev, the findings (they were also published in the journal Applied Physics Letters, the article named 'Influence of structural defects on the magnetocaloric effect in the vicinity of the first order magnetic transition in Fe50.4Rh49.6') will help to improve the applied uses of the MCE.

An alloy of iron and rhodium served as an object to study the MCE. As Radel Gimaev explained, this alloy was chosen for several reasons. The most interesting is that this material has the highest values of MCE of all known to date. 'In the scientific literature there are mentions of changing the temperature to 13K in magnetic fields up to 2 Tesla. On our sample with the same fields we received 7,5K,' said Radel Gimaev.

The maximum value of the MCE in it - as in all the magnets - is achieved under temperatures close to the phase transition temperature. In this case, the transition is from antiferromagnetic state with relatively weak magnetic properties into a ferromagnetic state.

In such alloys, the phase transition occurs at the temperatures close to a room temperature or human body temperature, which is very important for the prospective applications.

"In addition, the phase transition temperature of these alloys can be set with high accuracy by palladium or platinum doping" - tells the scientist.

Unfortunately, for the most promising option of the practical use for the MCE (magnetic refrigerator, which is now so widely discussed) this alloy is not relevant due to the high cost of rhodium. It should be noted that today the main obstacle to the commercialization of magnetic refrigerators is the high cost of the working element and the magnetic field sources. The scientists are seeking a way out in developing new relatively cheap materials with high magnetocaloric properties.

The perfect crystal structure for obtaining the maximum value of the MCE in iron-rhodium alloys is considered to be a body-centered cubic lattice (bcc), the unit cell of which is a set of iron atoms arranged at the vertices of a cube and rhodium atoms at its center.

It is worth adding that such a structure in the iron-rhodium alloys is formed only in the case of an equiatomic composition, i.e., composition with approximately equal amounts of iron and rhodium atoms.

To ensure such a bcc-structure, the samples were subjected to a 48-hour oven annealing at the temperature of 1000 degrees Celsius. However, the conducted measurements and used a theoretical model showed that in the bcc-structure of the alloys contained defects, namely the substitution of some (about 2%) of iron atoms with rhodium and vice versa.

As a result, the researchers showed that even such slight deviations from the ideal bcc-structure significantly alter the display of the magnetocaloric effect: the sample temperature changes approximately twice less and the phase transition temperatureshifts.

Moreover, the "irreversibility" effect was discovered when the final temperature of the alloy is not equal to the initial one after a complete cycle of the external magnetic field changes.

According to Gimaev, the conducted work will help to increase the effectiveness of the applied use of the magnetocaloric effect - it concerns both the need to bring the materials to the perfect, and the account of the observed irreversibility effect.

Secondly, he said, these studies reveal the previously unknown features of the phase transition of the first order in the studied alloys series and thereby deepen the understanding of the causes of the giant MCE in them.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once

credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only


Related Links
Lomonosov Moscow State University
Space Technology News - Applications and Research

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
Feeling the force between sand grains
Livermore CA (SPX) Aug 26, 2016
For the first time, Lawrence Livermore National Laboratory (LLNL) researchers have measured how forces move through 3D granular materials, determining how this important class of materials might pack and behave in processes throughout nature and industry. Granular materials such as sand, rice and soil exist everywhere around us. However, scientists and engineers do not yet fully understand ... read more

Space tourists eye $150mln Soyuz lunar flyby

Roscosmos to spend $7.5Mln studying issues of manned lunar missions

Lockheed Martin, NASA Ink Deal for SkyFire Infrared Lunar Discovery Satellite

As dry as the moon

Test for damp ground at Mars' seasonal streaks finds none

Fossilized rivers suggest warm, wet ancient Mars

China unveils 2020 Mars rover concept: report

MAVEN Spacecraft Gears Up to Observe Global Dust Storm on Mars

Grandpa astronaut breaks US space record

35 years later Voyager's legacy continues at Saturn

Chinese sci-fi prepares to master the universe

NASA Licenses New Auto-Tracking Mobile Antenna Platform

China unveils Mars probe, rover for ambitious 2020 mission

China Ends Preparatory Work on Long March 5 Next-Generation Rocket Engine

China launches hi-res SAR imaging satellite

China launches world first quantum satellite

Space Station's orbit adjusted Wednesday

Astronauts Relaxing Before Pair of Spaceships Leave

'New port of call' installed at space station

US astronauts prepare spacewalk to install new docking port

Russian Carrier Rocket for Sea Launches Will Replace Ukraine's Zenit

Intelsat "doubles down" with Arianespace for an Ariane 5 dual success

Kourou busy with upcoming Arianespace missions

Ariane 5 is approved for this week's Arianespace launch with two Intelsat payloads

Rocky planet found orbiting habitable zone of nearest star

A new Goldilocks for habitable planets

Venus-like Exoplanet Might Have Oxygen Atmosphere, but Not Life

Brown dwarfs reveal exoplanets' secrets

UNIST to engineer next-generation smart separator membranes

3-D-printed structures 'remember' their shapes

Berlin's IFA fair dons virtual reality headsets

New method developed for producing some metals

The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.