Sep 9, 2008 - NPG Asia Materials Magnetocaloric effect: Cool manganites ... are typically of the form RMnO3, where R is a rare earth element, have been.
10/26/2016
NPG Asia Materials Magnetocaloric effect: Cool manganites
Research Highlight Subject Category: Electronic, magnetic and superconducting materials NPG Asia Materials research highlight; doi:10.1038/asiamat.2008.114 Published online 9 September 2008
Magnetocaloric effect: Cool manganites Scientists in India are now exploring materials called manganites as an alternative route to ecofriendly refrigeration.
As anyone who has disposed of an old refrigerator knows, you have to be careful not to let the Freon gas leak out. Although modern refrigerators have replaced Freon with a less harmful liquid, other environmental cooling techniques are being actively explored. One novel possibility is to use magnets to extract heat away, where rather than going into the expansion of a gas—as in conventional refrigerators—the thermal energy goes into disordering the aligned spins of a magnet. This ‘magnetocaloric’ effect exists in a number of magnetic materials, but they are often expensive to produce or do not have the right properties at practical magnetic fields or temperatures. Now, a team of scientists in India is exploring the possibility of using materials known as manganites for magnetic refrigeration.1 Manganites, which are typically of the form RMnO3, where R is a rare earth element, have been widely studied because their resistance is highly sensitive to magnetic fields—a property useful for magnetic recording. For magnetic refrigeration, these materials are attractive because they are chemically inert and are expected to exhibit a large magnetocaloric effect—defined as the change in magnetic entropy and temperature—at relatively low magnetic fields. Prabhat Mandal and his colleagues looked specifically at the manganitem Sm0.52Sr0.48MnO3. Below about 120 K, a magnetic field can easily align the spins on the manganese sites so that if the magnetized material is allowed to come into thermal contact with a ‘hot’ object, then heat can depolarize the spins (Fig. 1).
http://www.nature.com/am/journal/2008/200809/full/am2008114a.html
1/3
10/26/2016
NPG Asia Materials Magnetocaloric effect: Cool manganites
Fig. 1: Flowchart of magnetic refrigeration in Sm0.52Sr0.48MnO3. Here, H is the magnetic field, Q is the heat transfer, T is the temperature and ΔTad is the temperature change when the spins depolarize (with no heat transfer). The group found a large magnetocaloric effect in Sm0.52Sr0.48MnO3 at about 1 Tesla. Compared to other possible materials for magnetic refrigerants—namely, other manganites and materials based on rare earth elements—Sm0.52Sr0.48MnO3 has one of the highest magnetocaloric effects at a relatively low magnetic field. Although the low operating temperature may limit their use to research applications, the study showed manganites to be a promising class of materials for magnetic refrigeration.
References 1. Parker, S., Mandal, P. & Choudhury, P. Large magnetocaloric effect in Sm0.52Sr0.48MnO3 in low magnetic field. Appl. Phys. Lett. 92, 182506 (2008). | Article |
This research highlight has been approved by the author of the original article and all empirical data contained within has been provided by said author.
NPG Asia Materials
ISSN (online) 18844057
http://www.nature.com/am/journal/2008/200809/full/am2008114a.html
2/3
10/26/2016
About us Contact us Accessibility statement Help
NPG Asia Materials Magnetocaloric effect: Cool manganites
Privacy policy Use of cookies Legal notice Terms
Naturejobs Nature Asia Nature Education RSS web feeds Search:
go
© 2016 Macmillan Publishers Limited, part of Springer Nature. All Rights Reserved. partner of AGORA, HINARI, OARE, INASP, ORCID, CrossRef, COUNTER and COPE
http://www.nature.com/am/journal/2008/200809/full/am2008114a.html
3/3
