2025/06/01 by Yamamoto, Takafumi D., Watanae, Tasuku, Labib, Farid +3 · 1 citation
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2506.00778
The magnetic response of the Tsai-type 1/1 Au-Al-Gd approximant crystals (ACs) was quantitatively investigated in terms of the magnetic entropy change (ΔSM) for different magnetic ground states. A comprehensive ΔSM map over a wide electron concentration range has been established, demonstrating the detailed variation of ΔSM across the entire magnetic phase diagram in the Tsai-type 1/1 ACs. Near the boundaries of the ferromagnetic (FM) phase, a clear deviation from the mean-field theory (MFT) was observed in both the Curie temperature (TC) and magnetic field (H) dependences of the maximum magnetic entropy change (ΔSMmax). Contrary to general expectations, a high ΔSMmax (7.2 J/K mol-Gd under a 5 T field variation), even comparable to those of candidate materials for low-temperature magnetic refrigeration, was obtained within the antiferromagnetic (AFM) region near the FM / AFM phase boundary. The unexpected enhancement of ΔSMmax toward the AFM region under high magnetic fields indicates an anomalous magnetic response in the present Tsai-type 1/1 AC, which is presumably associated with the breakdown of the MFT. The present finding suggests that tuning the magnetic ground state across the phase boundary is an effective strategy to enhance ΔSM, even in general rare-earth intermetallic compounds.