Progress and Prospect of Magnetic Refrigeration Alloys Near Room Temperature
LI Dongmei, ZUO Dingrong, YU Peng*
Photoelectric Functional Materials Key Laboratory of Chongqing, College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 401331, China
Abstract: Magnetic refrigeration technology is an advanced refrigeration technology with high efficiency, energy saving, environmental protection, and strong reliability. The core principle of the magnetocaloric effect is the physical phenomenon of that heat was released to the outside during isothermal magnetization and absorbed from the outside during adiabatic demagnetization of the magnetic refrigerant. Theoretically, all magnetic materials have the magnetocaloric effect. However, only a few magnetic materials with significant magnetocaloric effect can be used in magnetic refrigeration. Therefore, the research and development of magnetic refrigeration working medium with a larger magnetocaloric effect is the key factor to determine whether the magnetic refrigeration technology can be applied and promoted. After decades of development, many excellent magnetic refrigeration materials have been found, which promotes the development of magnetic refrigeration technology. At present, the magnetic refrigeration technology has been widely used, such as in the preparation of liquid Helium, low temperature physical research, and aerospace engineering, in the low temperature region below 20 K. The configurational entropy of magnetic refrigeration materials can be ignored in low temperature region as they are usually in paramagnetic state. However, with the temperature increasing, the influence of configurational entropy on the magnetic refrigeration cannot be ignored attributed to the lattice vibration of the paramagnetic materials becomes larger. So, the traditional paramagnetic refrigerant is no longer applicable near room temperature. Therefore, it is important to develop magnetic refrigeration materials near room temperature. In the past two decades, lots of studies on magnetic refrigeration materials near room temperature have carried out, such as the magnetic refrigeration materialsincluding Gd(SiGe)4, La(FeSi)13, MnAs alloy, and NiMn based Heusler alloy, and all those alloys present the first-order phase change and excellent magnetocaloric effect. The magnetocaloric effect of these alloys are usually caused by the superposition of structural phase change and magnetic phase change, but often accompanied by the large thermal and magnetic hysteresis, which will greatly reduce the efficiency of magnetic refrigeration. In addition to the magnetic refrigeration materials with first-order phase change, there are also magnetic refrigeration materials present second-order magnetic phase change,such as rare earth Gd and its compounds, Gd based amorphous alloys, and other magnetic refrigeration materials near room temperature. Among them, Gd based amorphous alloys have many advantages, such as a wide refrigeration temperature range, low eddy current loss, low hysteresis, wide composition range, corrosion resistance, and easy processing. Their wide refrigeration temperature range is particularly suitable for room temperature Ericsson cycle of magnetic refrigeration and has a broad application prospect. In this paper, the principle of magnetocaloric effect and the development of magnetic refrigeration technology are briefly introduced. The magnetocaloric properties and the latest research progress of magnetic refrigeration materials near room temperature are mainly introduced, including the magnetic refrigeration materials with first-order phase change, such as Gd(SiGe)4, La(FeSi)13, MnAs alloy, and NiMn based Heusler alloy and the Gd based amorphous alloy with second-order magnetic phase change. Their advantages as magnetic refrigeration materials are analyzed and the future development trend of each series of magnetic refrigeration materials is discussed.