Lecture

Magnetocaloric Effect: Applications and Materials

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In course

PHYS-491: Magnetism in materials

The lectures will provide an introduction to magnetism in materials, covering fundamentals of spin and orbital degrees of freedom, interactions between moments and some typical ordering patterns. Selected experimental techniques and their application in cu ...

Description

This lecture explores the magnetocaloric effect, discussing its applications at low and room temperatures. At low temperatures, adiabatic magnetization is achieved using liquid nitrogen or helium, dilution refrigerators, and paramagnetic salts. At room temperature, the focus is on finding materials for refrigeration that are commercially superior to compressed gas systems, with research emphasizing large temperature changes, minimal coolant mass, and avoidance of toxic or scarce materials. The lecture also delves into specific materials like the gadolinium selenium germanium alloy, showcasing unique ferromagnetic phase transitions and the potential for significant cooling effects.

Instructor

Ivica Zivkovic

Teaching & PhD PhD Students Berna Esmer Past EPFL PhD Students as codirector Virgile Favre, Bhushan Hegde, Yikai Yang Courses Magnetism in materials PHYS-491 The lectures will provide an introduction to magnetism in materials, covering fundamentals of spin and orbital degrees of freedom, interactions between moments and some typical ordering patterns. Selected experimental techniques and their application in current research will be presented.

Official source

Related concepts (29)

Magnetic refrigeration

Magnetic refrigeration is a cooling technology based on the magnetocaloric effect. This technique can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators. A magnetocaloric material warms up when a magnetic field is applied. The warming is due to changes in the internal state of the material releasing heat. When the magnetic field is removed, the material returns to its original state, reabsorbing the heat, and returning to original temperature.

Refrigeration

Refrigeration is any of various types of cooling of a space, substance, or system to lower and/or maintain its temperature below the ambient one (while the removed heat is ejected to a place of higher temperature). Refrigeration is an artificial, or human-made, cooling method. Refrigeration refers to the process by which energy, in the form of heat, is removed from a low-temperature medium and transferred to a high-temperature medium.

Vapor-compression refrigeration

Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services.

Ton of refrigeration

A ton of refrigeration (TR or TOR), also called a refrigeration ton (RT), is a unit of power used in some countries (especially in North America) to describe the heat-extraction capacity of refrigeration and air conditioning equipment. It was originally defined as the rate of heat transfer that results in the freezing or melting of of pure ice at in 24 hours. The modern definition is exactly . Air-conditioning and refrigeration equipment capacity in the U.S. is often specified in "tons" (of refrigeration).

Heat pump and refrigeration cycle

Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. A heat pump is a mechanical system that allows for the transmission of heat from one location (the "source") at a lower temperature to another location (the "sink" or "heat sink") at a higher temperature. Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink (as when warming the inside of a home on a cold day), or a "refrigerator" or “cooler” if the objective is to cool the heat source (as in the normal operation of a freezer).

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