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 ($\mathrm{\Delta }{S}_M$) for different magnetic ground states. A comprehensive $\mathrm{\Delta }{S}_M$ map over a wide electron concentration range has been established, demonstrating the detailed variation of $\mathrm{\Delta }{S}_M$ 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 ($T_{\mathrm{C}}$) and magnetic field ($H$) dependencies of the maximum magnetic entropy change ($\mathrm{\Delta }{S}_M^{\max }$). Contrary to general expectations, a high $\mathrm{\Delta }{S}_M^{\max }$ (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 $\mathrm{\Delta }{S}_M^{\max }$ 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 $\mathrm{\Delta }{S}_M$, even in general rare-earth intermetallic compounds.

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• Critical phenomena
• Magnetic phase transitions
• Magnetism
• Magnetocaloric effect
• RKKY interaction
• Alloys
• Intermetallic compounds
• Quasicrystals
• DC susceptibility measurements
• Magnetization measurements
• X-ray diffraction