First-order phase transitions and giant magnetocaloric effect

First-order phase transitions and giant magnetocaloric effect

Nguyen, T.T.

Brück, E.H. (promotor)

Applied Sciences

Radiation Radionuclides Reactors

2010-09-27

Modern society relies on cooling technology for food safety, comfort and medical applications. The solid-state cooling technology known as magnetic refrigeration is one of the most promising techniques to replace the current vapor-compression cooling technology. To date, the search for suitable materials with a large magnetocaloric effect (MCE) for domestic applications of magnetic refrigeration is still in progress. This thesis describes a study focused on magnetocaloric materials that can be used in magnetic refrigerators operating at room temperature. Understanding of the phase transition in these materials is of great important to create better materials. As a refrigerator is expected to operate at rather high cycle frequencies, large thermal hysteresis (?Thys) at the magnetic phase transition is the main obstacle to use a material for applications. We have been successful in tuning ?Thys of MnFe(P1-xGex) and related compounds to very small values, while maintaining a large MCE in a large range of working temperatures. These low-cost materials can be used as refrigerants working at high frequencies. This brings the use of practical magnetic cooling a step closer. On the other hand, we have discovered a near room-temperature giant MCE in a new class of magnetic materials based on the intermetallic MnCoGe alloy. The mechanism of manipulating the first-order magnetic phase transition in the MnCoGe-based alloys opens up new possibilities for searching novel magnetic refrigerants for room-temperature applications.

magnetocaloric effect
phase transition
magnetic refrigeration
intermetallic compounds

http://resolver.tudelft.nl/uuid:cdd138f9-227f-4a2a-b493-8667fa77dfee

9789085930815

Institutional Repository

doctoral thesis

(c) 2010 Nguyen, T.T.