Control of Covalent Bond Enables Efficient Magnetic Cooling

Area of Science:

• Materials Science
• Thermodynamics
• Sustainable Energy

Background:

• Magnetic cooling offers an energy-efficient and climate-friendly alternative to vapor-compression refrigeration, with lower global warming potential.
• Advancement of magnetic cooling is hindered by irreversible losses from hysteresis in magnetocaloric materials.
• Current methods to mitigate hysteresis often degrade cooling performance.

Purpose of the Study:

• To address the challenge of hysteresis in magnetocaloric materials.
• To develop a method for eliminating thermal hysteresis while maintaining or improving cooling performance.
• To enable efficient magnetic cooling for applications like gas liquefaction.

Main Methods:

• Formation of Sn(Ge)₃-Sn(Ge)₃ bonds within the unit cell of the Gd₅Ge₄ compound.
• Investigating the effect of these bonds on the material's phase transition and magnetocaloric properties.
• Measuring magnetic entropy change and reversible adiabatic temperature change.

Main Results:

• Elimination of thermal hysteresis through an energetically favorable phase transition.
• Synergistic improvement in magnetocaloric figures of merit in Gd₅Sn₂Ge₂.
• A twofold increase in reversible adiabatic temperature change (from 3.8 to 8 K) and enhanced magnetic entropy change.
• Achieved synergies are effective over a wide temperature range (40-160 K).

Conclusions:

• Demonstrated a novel approach to master hysteresis in magnetocaloric materials.
• Achieved simultaneous improvements in magnetocaloric metrics.
• Opens promising avenues for efficient gas liquefaction and sustainable energy solutions.