Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cooling towards absolute zero using super-heavy electrons

12.09.2016

New quantum material significantly improves adiabatic demagnetization cooling

To reach temperatures closely above absolute zero at −273.16 °C the demagnetization of magnetic materials under adiabatic, i.e., thermally insulated, conditions is utilized. Up to now, diluted magnetic salts have been used for this purpose. Researchers from Augsburg, Göttingen, Kyoto and Iowa State University report in „Science Advances“ on the discovery of a new metallic compound with super-heavy electrons, whose cooling efficiency significantly beats that of currently used paramagnetic salts.


Temperature evolution of an Yb0.81Sc0.19Co2Zn20 single crystal during the reduction of a magnetic field from 8 to 0 Tesla.

© University of Augsburg, IFP/EP VI

Fundamental research often requires very low temperatures, e.g. to investigate novel quantum effects in matter or to operate highly sensitive particle detectors. Usually the very rare 3-He isotope is utilized for cooling. It exhibits the lowest boiling point of matter but its price is extraordinary high. Over the last decade it increased more than tenfold.

Established: adiabatic demagnetization of paramagnetic salts

The adiabatic demagnetization method is a well-priced and uncomplicated alternative for using 3-He gas. It utilizes magnetic salts whose moments interact so weakly without magnetic field, that they are randomly oriented and order themselves only at very low temperatures. In a moderately large magnetic field the moments are aligned already at enhanced temperature. The entropy is a measure of the degree of disorder or misalignment of the moments. For cooling, the moments are therefore first aligned in a field, to reduce their entropy. Subsequently, the magnetic field is decreased to zero under adiabatic conditions that is without heat exchange to the environment. Because entropy remains constant during this processes, the material can only keep its low entropy if it cools down to very low temperatures.

Significant improvement of efficiency

Commercial adiabatic demagnetization uses paramagnetic salts. However, their thermal conductivity is so bad, that a network of metal wires has to be introduced to them, which significantly reduces the efficiency of the cooling substance per volume. Consequently, the physicists from Augsburg University together with collaborators from Göttingen University, Kyoto University and the Iowa State University intended to develop an alternative cooling substance with improved thermal conductivity. The new synthesized compound (Yb1-xScx)Co2Zn20 has the potential to significantly improve adiabatic demagnetization cooling.

Upon cooling a metal with magnetic moments, typically either ordering of the moments occurs or the moments are getting invalid due to their screening by the conduction electrons. In both cases the entropy is strongly reduced already at elevated temperatures preventing adiabatic demagnetization cooling to very low temperatures. “Aim of our research has been to avoid both effects simultaneously. If successful, it would enable effective cooling by a magnetic metal”, says Prof. Dr. Philipp Gegenwart, leader of the project at Augsburg University.

Formation of super-heavy electrons at low temperatures

The newly discovered (Yb1-xScx)Co2Zn20 fulfills all requirements for the desired properties. As shown in the attached sketch of its structure (inset), the magnetic Yb moments are surrounded by cages from Zn atoms. This structural arrangement is crucial. On the one hand, it hinders the screening of the Yb moments by the Co conduction electrons, on the other hand it also impedes the formation of long-range order. Consequently, the weak interaction of Yb moments and their environment leads to the formation of super-heavy electrons at low temperatures. A small dilution of the Yb atoms by non-magnetic Sc tunes the onset of magnetic order to exact zero temperature. Such a “quantum critical point” in principle allows for cooling down to absolute zero.

Even below 0.03 K

The data published in „Science Advances“ indicate that the new compound, developed by Gegenwart and his international team, cools very strongly during adiabatic demagnetization – even below the lowest measureable temperature 0.03 K of the used setup. Cooling efficiency and thermal conductivity of the new material are significantly better compared to that of magnetic salts evidencing its suitability for improving current low-temperature cooling devices.


Reference:
Y. Tokiwa, B. Piening, H. S. Jeevan, S.L. Bud’ko. P. C. Canfield, P. Gegenwart, Super-heavy electron material as metallic refrigerant for adiabatic demagnetization cooling. Sci. Adv. 2, e1600835 (2016).

Contact:
Prof. Dr. Philipp Gegenwart
Lehrstuhl für Experimentalphysik VI/EKM
Institut für Physik / Zentrum für Elektronische Korrelationen und Magnetismus
Universität Augsburg
86135 Augsburg
Telefon +49(0)821/598-3650
philipp.gegewart@physik.uni-augsburg.de

Weitere Informationen:

http://advances.sciencemag.org/content/advances/2/9/e1600835.full.pdf

Klaus P. Prem | idw - Informationsdienst Wissenschaft
Further information:
http://www.uni-augsburg.de/

Further reports about: Electrons magnetic field metallic thermal conductivity

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>