Magnetic and Transport Anomalies and Large Magnetocaloric Effect in Cubic R4PtAl (R = Ho and Er)

We report the electronic properties of R4PtAl (R = Ho, and Er), which contains three sites for R, by the measurements of magnetization (ac and dc), heat-capacity, transport, and magnetoresistance (MR). Dc magnetization data reveal antiferromagnetic order below 19 K and 12 K in Ho and Er compounds, respectively. Additional features observed at lower temperatures (12 K for Ho4PtAl and 5 K for Er4PtAl) are akin to the cluster spin-glass phase. Resistivity data exhibit a weak minimum at a temperature marginally higher than their respective Neel temperature (T-N), which is unusual for such rare-earths with well-localized 4f states. Isothermal magnetization and magnetoresistance data well below T-N exhibit signatures of a subtle field-induced magnetic transition for a small magnetic field (<10 kOe). Notably, the isothermal entropy change at T-N has the largest peak value within this rare-earth family; for a field change from zero to 50 kOe, the entropy change is similar to 14.5 J/kg K (Ho4PtAl) and similar to 21.5 J/kg K (Er4PtAl) suggesting a role of anisotropy of 4f orbital in determining this large value. The results provide some clues for the advancement of the field of magnetocaloric effect. The magnetocaloric property of Er4PtAl is nonhysteretic, meeting a challenge to find materials with reversible magnetocaloric effect.

Automated summary

We investigate the electronic properties of R4PtAl (R = Ho and Er) using various measurements. Our results show antiferromagnetic order in Ho and Er compounds, as well as the presence of a spin-glass phase at lower temperatures. The resistivity data exhibit a weak minimum slightly above the respective Néel temperature, which is unusual for rare-earth materials with well-localized 4f states. We also observe a subtle field-induced magnetic transition and a large isothermal entropy change for both compounds. These findings provide insights for the development of magnetocaloric materials.