Magnetocaloric Materials and Magnetic Refrigeration Systems

Magnetocaloric materials exhibit a reversible temperature change under varying magnetic fields, a phenomenon known as the magnetocaloric effect (MCE). This effect stems from the coupling between magnetic moment alignment and thermal entropy, whereby the application or removal of a magnetic field induces heating or cooling. Key alloy systems—including gadolinium‐based intermetallics, La(Fe,Si)13 compounds, Mn‐based materials and rare‐earth transition‐metal frameworks—have been engineered to deliver substantial magnetic entropy changes and adiabatic temperature shifts across a wide range of operating temperatures. Magnetic refrigeration systems employ active magnetic regenerators (AMRs) that cycle these materials through magnetisation and demagnetisation phases, transferring heat between hot and cold reservoirs without the need for greenhouse‐gas refrigerants. Challenges under investigation include reducing thermal and magnetic hysteresis, enhancing heat‐exchange interfaces, and designing efficient permanent magnet assemblies to provide high magnetic flux at low energy cost. Recent advances in multicaloric cycles, hybrid magneto‐baro caloric materials and machine‐learning‐driven discovery are accelerating the translation of laboratory‐scale prototypes into practical, energy‐efficient refrigeration and cryogenic cooling solutions.

Research from Nature Portfolio

Recent studies have unveiled Er(Ho)Co2‐based alloys that exhibit a giant magnetocaloric effect tailored for hydrogen liquefaction applications. By eliminating the magnetostructural transition, these compounds achieve a reversible magnetic entropy change exceeding 0.2 J cm−3 K−1 across the 20–77 K range, enabling continuous operation in cryogenic cycles. A new quantitative criterion for classifying the order of magnetic phase transitions introduces a model‐independent fingerprint—an exponent n > 2 in the field dependence of entropy change—which reliably distinguishes first‐order behaviour without subjective data interpretation. Integration of dual‐stimulus multicaloric cycles in FeRh thin films, coupled to ferroelectric substrates, has demonstrated significantly reduced magnetic hysteresis losses and enhanced reversible adiabatic temperature changes. This multicaloric approach highlights a viable pathway towards efficient, low‐loss solid‐state refrigeration devices.

Magnetocaloric Materials and Magnetic Refrigeration Systems publication trend

The graph below shows the total number of articles in magnetocaloric materials and magnetic refrigeration systems across all publications each year (not limited to Nature Index journals).

Technical terms

Magnetocaloric effect: Reversible temperature change in a magnetic material upon application or removal of a magnetic field due to changes in magnetic entropy.

Magnetic entropy change (ΔSm): Measure of the variation in entropy when a material is magnetised or demagnetised, directly linked to its cooling power.

Adiabatic temperature change (ΔTad): Temperature shift experienced by a material under adiabatic magnetisation or demagnetisation conditions.

Active magnetic regenerator (AMR): Heat‐exchange assembly that alternates magnetocaloric material between magnetised and demagnetised states to transfer heat between reservoirs.

First‐order phase transition: Abrupt change in magnetic order associated with latent heat release and often accompanied by hysteresis, yielding large caloric effects.

Hysteresis: Energy loss and lag in material response due to history‐dependent behaviour during cyclic magnetic or structural transitions.

References

1. Energy Applications of Magnetocaloric Materials. Advanced Energy Materials (2020).
2. A quantitative criterion for determining the order of magnetic phase transitions using the magnetocaloric effect. Nature Communications (2018).
3. Making a Cool Choice: The Materials Library of Magnetic Refrigeration. Advanced Energy Materials (2019).
4. Large reversible caloric effect in FeRh thin films via a dual-stimulus multicaloric cycle. Nature Communications (2016).
5. Magnetic refrigeration material operating at a full temperature range required for hydrogen liquefaction. Nature Communications (2022).
6. Machine-learning-guided discovery of the gigantic magnetocaloric effect in HoB2 near the hydrogen liquefaction temperature. NPG Asia Materials (2020).