Futuristic cooling system using AlFe2B2 material.

Magnetocaloric Marvel: Can This Affordable Compound Replace Rare Earths in Cooling Tech?

Elliot Brynn in Science & Nature August 2025 • 4 min read.

"Unlocking the potential of AlFe2B2: A deep dive into its magnetic properties and how it could revolutionize magnetic refrigeration, offering a sustainable alternative to expensive rare earth materials."

The quest for efficient and environmentally friendly cooling technologies has led researchers to explore alternatives to traditional gas expansion systems. These systems, while effective, contribute to environmental damage, spurring the search for cleaner solutions. Magnetic refrigeration, leveraging the magnetocaloric effect (MCE), has emerged as a promising candidate.

Magnetic refrigeration eliminates harmful synthetic refrigerants like chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and hydrochlorofluorocarbons (HCFCs). The focus has shifted towards developing advanced solid magnetic refrigerants, rigorously tested in functional magnetocaloric devices. This parallel effort has also spurred innovation in cooling device design, signaling a move towards sustainable cooling technologies.

A key factor in magnetic refrigeration is finding materials with a large MCE that can operate under relatively low magnetic fields (less than 2T), achievable with permanent magnets. This has led to research into compounds like Gd5Si4-xGex, LaFe13-xSix, Yo.4Gd0.6C02, and MnFeP(As, Ge). Among these, the intermetallic compound AlFe2B2 stands out due to its potential as a cost-effective alternative to gadolinium, which faces rising prices due to its rare earth classification.

AlFe2B2: A Cost-Effective Magnetocaloric Material

Futuristic cooling system using AlFe2B2 material.

The intermetallic compound AlFe2B2, synthesized in 1969 by Jeitschko, has garnered attention for its potential in magnetic refrigeration. Belonging to the AIM2B2 materials class (M = Fe, Mn, Cr), AlFe2B2 has been identified as having an orthorhombic structure with either ferromagnetic or paramagnetic properties at room temperature.

Researchers, including Kadas et al., have studied the phase stability of AlM2B2 materials, finding that compounds with M = Cr, Mn, and Fe are stable. AlFe2B2 itself crystallizes in an orthorhombic structure (space group Cmmm, No 65) with specific cell parameters, and the positions of aluminum, iron, and boron atoms are precisely defined.

Crystal Structure: Orthorhombic (Cmmm)
Cell Parameters: a = 2.923(10) Å, b = 11.0337(14) Å, c = 2.8703(3) Å
Atomic Positions: Aluminum, iron, and boron atoms occupy specific positions within the crystal lattice.

Theoretical studies by Cheng et al. have explored the structural, electronic, and elastic properties of AlFe2B2. The Curie temperature (Tc) of AlFe2B2, the point at which it transitions between ferromagnetic and paramagnetic states, varies between 282 K and 320 K. Cedervall's study reported a Curie temperature of 299 K using Mössbauer spectroscopy. The magnetic moment of iron in this compound is calculated to be 1.25 µB, and it exhibits a large magnetic entropy change, making it suitable for magnetic refrigeration applications.

The Future of AlFe2B2 in Magnetic Refrigeration

The research indicates that AlFe2B2 holds promise as a viable material for magnetic refrigeration, particularly due to its cost-effectiveness and the abundance of its constituent elements. Further studies and improvements could enhance its performance, making it a competitive alternative to rare earth-based materials in cooling technology. The findings suggest that AlFe2B2 and its derivatives could significantly contribute to more sustainable and economically feasible magnetic refrigeration systems.

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This article is based on research published under:

DOI-LINK: 10.1016/j.intermet.2018.10.025, Alternate LINK

Title: Magnetocaloric And Cooling Properties Of The Intermetallic Compound Alfe2B2 In An Amr Cycle System

Subject: Materials Chemistry

Journal: Intermetallics

Publisher: Elsevier BV

Authors: A. El Boukili, N. Tahiri, E. Salmani, H. Ez-Zahraouy, M. Hamedoun, A. Benyoussef, M. Balli, O. Mounkachi

Published: 2019-01-01

Everything You Need To Know

What is AlFe2B2, and why is it being considered for magnetic refrigeration?

AlFe2B2 is an intermetallic compound belonging to the AIM2B2 materials class, where M can be iron (Fe), manganese (Mn), or chromium (Cr). It is being explored for magnetic refrigeration due to its potential as a cost-effective alternative to rare-earth materials like gadolinium. Its orthorhombic crystal structure and magnetic properties, including a Curie temperature between 282 K and 320 K and a magnetic moment of iron at 1.25 µB, make it suitable for this application. Moreover, AlFe2B2's composition with abundant elements makes it a sustainable choice compared to materials relying on scarce resources.

How does magnetic refrigeration work, and what role does the magnetocaloric effect (MCE) play?

Magnetic refrigeration utilizes the magnetocaloric effect (MCE), where a material's temperature changes in response to a changing magnetic field. This technology offers a cleaner alternative to traditional gas expansion systems, which use environmentally harmful refrigerants like chlorofluorocarbons (CFCs). A key component of magnetic refrigeration is finding materials with a significant MCE that can function effectively under low magnetic fields (less than 2T). AlFe2B2 is being investigated because of its ability to exhibit the MCE and its potential to provide efficient cooling.

What are the key magnetic properties of AlFe2B2, and how do they contribute to its suitability for refrigeration?

AlFe2B2 exhibits specific magnetic characteristics that are crucial for magnetic refrigeration. It has a Curie temperature (Tc) between 282 K and 320 K, which is the temperature at which it transitions between ferromagnetic and paramagnetic states. The magnetic moment of iron within the compound is calculated to be 1.25 µB. The compound also exhibits a large magnetic entropy change. These properties make AlFe2B2 a strong candidate for magnetic refrigeration. The Curie temperature is particularly important, as it defines the temperature range where the material can effectively function as a refrigerant.

What advantages does AlFe2B2 offer over traditional refrigerants and rare-earth materials like gadolinium?

AlFe2B2 offers several advantages. Unlike traditional gas expansion systems using harmful refrigerants such as chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and hydrochlorofluorocarbons (HCFCs), magnetic refrigeration with AlFe2B2 is environmentally friendly. Furthermore, it presents a cost-effective alternative to gadolinium, a rare-earth element, which faces price volatility. The use of AlFe2B2, composed of more abundant elements, promotes sustainable cooling technology and reduces reliance on scarce resources.

What is the crystal structure of AlFe2B2, and how does this influence its properties?

AlFe2B2 has an orthorhombic crystal structure, specifically belonging to the Cmmm space group (No. 65). This structure is defined by specific cell parameters: a = 2.923(10) Å, b = 11.0337(14) Å, and c = 2.8703(3) Å. The precise arrangement of aluminum, iron, and boron atoms within this structure dictates the material's magnetic and thermal properties, including its Curie temperature and its response to magnetic fields. The structural characteristics play a crucial role in determining its magnetocaloric effect, which is essential for its function in magnetic refrigeration.