Publications & Results

Design of thermal hysteresis in nonstoichiometric Fe2P-type alloys with giant magnetocaloric effect

Sagar Ghorai, Rebecca Clulow, Johan Cedervall, Shuo Huang, Tore Ericsson, Lennart Häggström, Ridha Skini, Vitalii Shtender, Levente Vitos, Olle Eriksson, Franziska Scheibel, Konstantin Skokov, Oliver Gutfleisch, Martin Sahlberg, Peter Svedlindh

Physical Review B

Results highlighted in this publication:

The study demonstrates that nonstoichiometry in Fe₂P-type alloys provides a powerful control parameter for magnetoelastic coupling, enabling the tuning of thermal hysteresis and mechanical stability without compromising the giant magnetocaloric response. Strong magnetoelastic interactions give rise to large isothermal entropy changes (Fig. a). Mössbauer spectroscopy reveals that both the average hyperfine field in the ferromagnetic state and the average centre shift in the paramagnetic state decrease in parallel with the entropy change, indicating a direct link between local electronic structure and macroscopic caloric response. Increasing nonstoichiometry further enhances mechanical stability by reducing the lattice volume change across the magnetoelastic phase transition (inset of Fig. a). The adiabatic temperature change of one of the alloys is 1.7 K at 1.9 T applied filed. The findings demonstrate a pathway toward more efficient and sustainable 𝐬𝐨𝐥𝐢𝐝-𝐬𝐭𝐚𝐭𝐞 𝐫𝐞𝐟𝐫𝐢𝐠𝐞𝐫𝐚𝐭𝐢𝐨𝐧 𝐧𝐞𝐚𝐫 𝐫𝐨𝐨𝐦 𝐭𝐞𝐦𝐩𝐞𝐫𝐚𝐭𝐮𝐫𝐞.

(a) Temperature dependent isothermal entropy change measured at 2 T (hollow symbols) and 5 T (solid symbols) applied fields, respectively of (FeMnP_0.5Si_0.5)₁₋_𝑥(FeV)_𝑥 alloys. Inset shows the change in lattice volume (b) Average center shift ( 𝐶𝑆) and hyperfine field ( 𝐵_ℎ𝑓) values obtained from Mössbauer spectra at 410 and 100 K, respectively. (c) Temperature dependent adiabatic temperature change for the 𝑥=0.02 alloy, measured at 1.9 T.

© Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Revealing complex magnetic interactions in Fe2P-based compounds: a study using Mössbauer spectroscopy and neutron diffraction

Karthika K. Thilakan, Sagar Ghorai, Wei Liu, Lennart Häggström, Fredrik Lindgren, Vladimir Pomjakushin, Premysl Beran, Oliver Gutfleisch, Peter Svedlindhgh and Johan Cedervall

Journal of Materials Chemistry A

Results highlighted in this publication:

Subtle chemical substitution reshapes magnetic order in Fe₂P-derived materials. The combined use of Mössbauer spectroscopy, magnetometry, and neutron diffraction reveals how subtle Mn and Si substitutions in Fe₂P drastically alter the magnetic ground state — ranging from ferromagnetism to complex incommensurate antiferromagnetism with glassy spin dynamics. These findings establish composition–structure–magnetism design principles for Fe₂P-based functional materials, and are crucial for understanding and developing 𝘀𝘂𝘀𝘁𝗮𝗶𝗻𝗮𝗯𝗹𝗲 𝗺𝗮𝗴𝗻𝗲𝘁𝗶𝗰 𝗺𝗮𝘁𝗲𝗿𝗶𝗮𝗹𝘀, especially for applications in 𝗺𝗮𝗴𝗻𝗲𝘁𝗶𝗰 𝗿𝗲𝗳𝗿𝗶𝗴𝗲𝗿𝗮𝘁𝗶𝗼𝗻 due to their significant magnetocaloric effect.

Quaternary phase diagram of the Fe–Mn–P–Si system. The samples studied in this paper lie on the dotted line. Magnetic structure depicting the propagation of magnetic moments along a-axis. Fe I atoms sitting at the 3f site are shown inside polyhedra .

Magnetic and mechanical hardening of nano-lamellar magnets using thermo-magnetic fields

Liuliu Han, Jin Wang, Nicolas J. Peter, Fernando Maccari, András Kovács, Ruth Schwaiger, Oliver Gutfleisch & Dierk Raabe

Journal: Nature Communications

Results highlighted in this publication:

High-performance magnets are essential for energy conversion technologies, but their reliance on rare-earth elements comes with high costs and supply risks. The new study, published in Nature Magazine, presents a promising alternative.

By introducing nano-lamellar structures into a Co-Fe-Ni-Al material system using thermo-magnetic field processing, the scientists achieved simultaneous improvements in magnetic and mechanical performance. This innovation not only enhances coercivity and mechanical strength but also paves the way for more durable, high-efficiency magnets – ideal for high-speed motors and generators in harsh conditions.

The study aligns closely with the objectives of the CoCoMag project, which aims to develop next-generation magnetic materials that are both high-performing and sustainable.

Magnetic and mechanical hardening of nano-lamellar magnets using thermo-magnetic fields, Nat Commun 16, 2423 (2025), Authors: Liuliu Han, Jin Wang, Nicolas J. Peter, Fernando Maccari, András Kovács, Ruth Schwaiger, Oliver Gutfleisch & Dierk Raabe

Perspectives and Energy Applications of Magnetocaloric, Pyromagnetic, Electrocaloric, and Pyroelectric Materials

K. Klinar, J.Y. Law, V. Franco, X. Moya, A. Kitanovski

Journal: Advanced Energy Materials

Results highlighted in this publication:

This perspective paper outlines the current state-of-the-art and emerging directions in magneto- and electro-caloric materials and cooling devices, with particular relevance to the goals of CoCoMag Project. A review of the past five years of literature reveals a clear shift toward the exploration of compositionally complex alloys, the development of mechanically robust compounds, the pursuit of novel device architectures, and the expansion of magnetocaloric technologies into low-temperature applications. These trends reflect a growing emphasis on both performance and practicality—principles that align closely with CoCoMag Project’s mission to design next-generation magnetic materials and systems through sustainable, innovative approaches.

Advanced Energy Materials, Vol14, Issue 39, Perspectives and Energy Applications of Magnetocaloric, Pyromagnetic, Electrocaloric, and Pyroelectric Materials,
Authors: K. Klinar, J.Y. Law, V. Franco, X. Moya, A. Kitanovski,

Modern rare-earth-containing magnetocaloric materials: standing on the shoulders of giant Gd5Si2Ge2

J.Y. Law, V. Franco

Journal: Handbook on the Physics and Chemistry of Rare Earths, Commemorative Volume to late Vitalij K. Pecharsky, Elsevier

Results highlighted in this publication:

This commemorative volume honors the legacy of Prof. Vitalij Pecharsky by celebrating the rich chemistry and physics he helped advance. We pay tribute to his codiscovery of the giant magnetocaloric Gd₅Si₂Ge₂. This magnetocaloric effect describes the heating or cooling of materials under a varying magnetic field, paving the way for alternative energy-efficient cooling technologies. We explore how this discovery continues to influence the development of modern magnetocaloric materials, focusing on those that meet the giant GMCE threshold. A central theme is material criticality—the careful balance between achieving high performance and ensuring sustainability. Our focus includes emerging compositionally complex alloys that reduce rare-earth dependence while maintaining functional efficiency. These materials offer promising solutions for applications like gas liquefaction, where current technologies rely heavily on non-abundant rare-earth based compounds. Our findings outline a viable design space that avoids extreme criticality, aligning closely with CoCoMag Project’s mission to develop next-generation magnetic materials through innovative and eco-conscious compositionally complex alloying approaches.

Handbook on the Physics and Chemistry of Rare Earths, Vol 64, 2023, Pages 175-246, Chapter 332 – Modern rare-earth-containing magnetocaloric materials:
Standing on the shoulders of giant Gd5Si2Ge2, Authors: Jia Yan Law, Victorino Franco,

Stress-relieved Fe-Mn-Ni-Ge-Si high-entropy alloys: a path for enhancing the magnetocaloric response

Á. Díaz-García, J.Y. Law, L.M. Moreno-Ramírez, V. Franco

Journal: Scripta Materialia

Results highlighted in this publication:

In our latest article, we’ve made exciting improvements to our previously developed FeMnNiGeSi magnetocaloric high-entropy alloys (HEAs), recognized as the third generation of HEAs, which show great promise for sustainable cooling. By applying low-temperature heat treatments, we significantly improved their magnetocaloric effects and transition temperatures, without altering their composition or microstructure. This breakthrough outperforms previous materials and positions these alloys as strong contenders for advanced cooling technologies.

What’s even more exciting is that our research uncovers that stress relaxation plays a major role in boosting performance. Our findings suggest that optimizing stress in the material can be even more impactful than simply achieving a single-phase structure, which has traditionally been the focus in HEA development. This work advances our CoCoMag Project’s initiative, where we are developing innovative, compositionally complex alloys that do not rely on a single-phase structure to perform at their best.

Reprinted from Scripta Materialia, Vol 258, Authors: Álvaro Díaz-García,Jia Yan Law,Luis M. Moreno-Ramírez,Victorino Franco, Stress-relieved Fe-Mn-Ni-Ge-Si
high-entropy alloys: a path for enhancing the magnetocaloric response