Magnetocaloric properties, magnetic interactions and critical behavior in Ho6(Fe,Mn)Bi2 intermetallics

• Published in: Journal of alloys and compounds 2020-04, Vol.821, p.153198, Article 153198
• Main Authors: Herrero, A., Oleaga, A., Salazar, A., Garshev, A.V., Yapaskurt, V.O., Morozkin, A.V.
• Format: Article
• Language: English
• Subjects: Critical behavior; Entropy; Ferromagnetism; Intermetallic compounds; Long range order; Magnetic materials; Magnetic properties; Magnetocaloric effect; Manganese; Rare earth compound; Refrigeration; Scaling laws; Spin-ordering
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.153198

Four polycrystaline Fe2P-type Ho6(Fe,Mn)Bi2 intermetallic compounds (space group P6‾2m, No. 189, hP9) have been studied using magnetic techniques in order to explore their ability as magnetocaloric materials, and study the critical behavior of the paramagnetic (PM) to ferromagnetic (FM) transitions to obtain a deeper understanding of the range of the magnetic interactions. The obtained critical exponents β, γ and δ for the four compounds studied (Ho6MnBi2, Ho6FeBi2, Ho6(Mn0.5Fe0.5)Bi2, Ho6(Mn0.75Fe0.25)Bi2) point to long-range order interactions, as they are close to those of the Mean Field Universality class. All of the compounds show relevant magnetocaloric properties over a very broad temperature range, limited by the PM-FM transition and a spin-reorientation one, well separated in all cases. They present very high values of the refrigerant capacities (from 520 J/kg to 709 J/kg at 5 T), good magnetic entropy changes (from 3.4 to 5.7 J/(kgK) at 5 T), and a flat and wide temperature span for the working temperature range (nearly 200 K for Ho6MnBi2, 80 K for Ho6FeBi2 at 5T). The change in properties with composition proves that the magnetocaloric properties can be tuned in Fe2P-type compounds to accommodate different refrigeration applications. Finally, the magnetocaloric scaling laws have been successfully tested and universal curves for the magnetic entropy change have also been obtained in the PM-FM transition region. •Second order FM to PM transition, long-range order interactions involved.•Very high values of the refrigerant capacities from 520 J/kg to 709 J/kg at 5T•Good magnetic entropy changes from 3.4 to 5.7 J/(kgK) at 5T•Flat and wide temperature span for the working temperature range (up to 200 K).•Magnetocaloric scaling laws tested and universal curves obtained.