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Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials
Published on: January 21, 2016
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Giant Low-Field Magnetocaloric Effect at Sub-Kelvin Temperatures in Ferromagnetic NH4GdF4
Qing Guo1,2, Weijun Ren1, Peng Liu1
1Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, Liaoning, People's Republic of China.
Journal of the American Chemical Society
|September 11, 2025
Summary
A new rare-earth fluoride, ammonium gadolinium fluoride (NH4GdF4), shows superior performance as a cryogenic refrigerant for helium-free adiabatic demagnetization refrigeration (ADR). Its enhanced magnetocaloric effect surpasses benchmarks like GGG, enabling advanced low-temperature research.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Cryogenics
Background:
- Adiabatic demagnetization refrigeration (ADR) requires advanced materials for sub-Kelvin cooling.
- Gadolinium gallium garnet (Gd3Ga5O12 or GGG) is a standard refrigerant, but improved alternatives are sought.
- Helium-free cooling is essential for space-based and quantum computing applications.
Purpose of the Study:
- To explore novel rare-earth fluorides as potential cryogenic refrigerants.
- To evaluate the magnetocaloric properties of NH4GdF4 for low-field ADR.
- To compare the performance of NH4GdF4 against established refrigerants like GGG.
Main Methods:
- Synthesis and characterization of ammonium gadolinium fluoride (NH4GdF4).
- Measurement of magnetic entropy change and adiabatic temperature change under varying magnetic fields.
- Analysis using nearest neighbor exchange interaction models and specific heat measurements.
Main Results:
- NH4GdF4 exhibits a ferromagnetic ground state ordering at 0.85 K.
- It shows a significantly stronger low-field magnetocaloric effect than GGG.
- Achieved magnetic entropy change of 38.2 J·kg−1·K−1 and temperature change of 1.1 K under a 0-10 kOe field swing.
Conclusions:
- NH4GdF4 is a highly promising refrigerant for low-field ADR systems.
- Its superior performance enables advancements in condensed matter physics and quantum technologies.
- This material offers a competitive alternative for sub-Kelvin cooling applications.
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