Featured Research

from universities, journals, and other organizations

Materials: Magnetic mystery solved

Date:
March 27, 2013
Source:
The Agency for Science, Technology and Research (A*STAR)
Summary:
Defects in metal–organic frameworks induce low-temperature ferromagnetism and could yield novel materials for industry.

Highly porous materials known as metal-organic frameworks (MOFs) are showing promise as catalysts and drug-delivery vehicles. Some scientific sleuthing by A*STAR researchers could now help industry to exploit the magnetic properties of MOFs for applications such as biomedical sensors.

The structure of MOFs resembles atomic scaffolding: clusters of atoms containing metal ions are linked together in a three-dimensional lattice by carbon-based aromatic molecules (see image). One particular MOF -- known as HKUST-1 -- has attracted attention because it was unexpectedly found to be ferromagnetic, albeit at the low temperature of -268.45 °C or less.

Each metal cluster in the material contains a pair of copper ions held together by four carboxylate groups, which contain carbon and oxygen atoms. Each metal ion carries an unpaired electron, which acts like a tiny bar magnet. The magnetic fields of the two unpaired electrons in a cluster would normally oppose each other -- the 'north' of one electron lining up with the 'south' of its neighbor -- negating any overall magnetism. Even if one copper cluster became magnetic, it would have to align with many other clusters throughout the material to produce ferromagnetism. Yet the organic linker molecules hold the clusters too far apart for the clusters to influence each other directly.

An international team led by Shuo-Wang Yang of the A*STAR Institute of High Performance Computing in Singapore and Lei Shen of the National University of Singapore has now solved the mysterious origin of the ferromagnetism2. By modeling the behaviors of ions and electrons in a series of MOFs, the team showed that if a copper ion is absent from a cluster, its carboxylate group will carry an unpaired, magnetic electron instead. Its magnetic field affects itinerant electrons in the MOF's organic linkers, which in turn affect any unpaired electrons in the next copper cluster. If the magnetic message reaches enough clusters, the material as a whole becomes ferromagnetic.

The researchers made a range of MOFs containing the twin copper motif, and found that around 0.57% of the metal ions were indeed missing from the structure -- enough to generate ferromagnetism at low temperatures, they calculated. Such copper vacancies are "inevitable, especially for large organic-metal complex systems such as MOFs," the researchers note.

Yang and co-workers also predicted that a MOF containing a non-aromatic organic linker that blocks the magnetic coupling between two adjacent clusters, and confirmed by experiments that it was not ferromagnetic. The researchers now hope to create new ferromagnetic materials by designing MOFs with deliberate metal-ion vacancies.

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing.


Story Source:

The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.


Journal Reference:

  1. Lei Shen, Shuo-Wang Yang, Shengchang Xiang, Tao Liu, Bangchuan Zhao, Man-Fai Ng, Jörg Göettlicher, Jiabao Yi, Sean Li, Lan Wang, Jun Ding, Banglin Chen, Su-Huai Wei, Yuan Ping Feng. Origin of Long-Range Ferromagnetic Ordering in Metal–Organic Frameworks with Antiferromagnetic Dimeric-Cu(II) Building Units. Journal of the American Chemical Society, 2012; 134 (41): 17286 DOI: 10.1021/ja3077654

Cite This Page:

The Agency for Science, Technology and Research (A*STAR). "Materials: Magnetic mystery solved." ScienceDaily. ScienceDaily, 27 March 2013. <www.sciencedaily.com/releases/2013/03/130327162422.htm>.
The Agency for Science, Technology and Research (A*STAR). (2013, March 27). Materials: Magnetic mystery solved. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2013/03/130327162422.htm
The Agency for Science, Technology and Research (A*STAR). "Materials: Magnetic mystery solved." ScienceDaily. www.sciencedaily.com/releases/2013/03/130327162422.htm (accessed October 22, 2014).

Share This



More Matter & Energy News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Jet Sales Lift Boeing Profit 18 Pct.

Jet Sales Lift Boeing Profit 18 Pct.

Reuters - Business Video Online (Oct. 22, 2014) — Strong jet demand has pushed Boeing to raise its profit forecast for the third time, but analysts were disappointed by its small cash flow. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Internet of Things Aims to Smarten Your Life

Internet of Things Aims to Smarten Your Life

AP (Oct. 22, 2014) — As more and more Bluetooth-enabled devices are reaching consumers, developers are busy connecting them together as part of the Internet of Things. (Oct. 22) Video provided by AP
Powered by NewsLook.com
Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Newsy (Oct. 21, 2014) — If you've ever watched "Back to the Future Part II" and wanted to get your hands on a hoverboard, well, you might soon be in luck. Video provided by Newsy
Powered by NewsLook.com
Robots to Fly Planes Where Humans Can't

Robots to Fly Planes Where Humans Can't

Reuters - Innovations Video Online (Oct. 21, 2014) — Researchers in South Korea are developing a robotic pilot that could potentially replace humans in the cockpit. Unlike drones and autopilot programs which are configured for specific aircraft, the robots' humanoid design will allow it to fly any type of plane with no additional sensors. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins