Large reversible magnetocaloric effect in antiferromagnetic Ho₂O₃ powders

Area of Science:

• Materials Science
• Condensed Matter Physics
• Thermodynamics

Background:

• Giant magnetocaloric materials are crucial for magnetic refrigeration technologies.
• First-order magnetic transition materials exhibit giant magnetocaloric effects but suffer from hysteresis and irreversibility.
• There is a need for materials with giant magnetocaloric effects that overcome these limitations.

Purpose of the Study:

• To investigate the magnetocaloric properties of commercialized Holmium oxide (Ho2O3).
• To determine if Ho2O3 exhibits a giant magnetocaloric effect without hysteresis losses at low temperatures.
• To evaluate the potential of Ho2O3 for magnetic refrigeration applications.

Main Methods:

• Experimental investigation of magnetic and magnetocaloric properties of Ho2O3.
• Characterization of magnetic transitions, specifically identifying the Néel temperature.
• Calculation of magnetic entropy change and refrigerant capacity under applied magnetic fields.

Main Results:

• A giant magnetocaloric effect was observed in Ho2O3 at approximately 2K.
• Ho2O3 exhibits a second-order antiferromagnetic transition with a Néel temperature of 2K.
• At 5T and below 3.5K, maximum magnetic entropy change reached 31.9 J.K-1.kg-1 and refrigerant capacity was 180 J.K-1, with no hysteresis losses.

Conclusions:

• Commercialized Ho2O3 demonstrates a giant magnetocaloric effect at low temperatures without hysteresis.
• The absence of hysteresis and irreversibility makes Ho2O3 a promising candidate for practical magnetic refrigeration.
• This discovery offers a viable alternative to traditional magnetocaloric materials for low-temperature cooling applications.