High pressure study of magnetocaloric effect in Ho3Co and Tb3Co

The magnetocaloric effect of intermetallic compounds of Tb3Co and Ho3Co is studied under high pressures up to ∼1 GPa using pressure dependent dc magnetisation and specific heat measurements at ambient conditions. The magnetic entropy change (−ΔSM) obtained from magnetisation data and adiabatic change in temperature (ΔTad) determined from zero-field specific heat and magnetisation data are found to be nearly identical within error limits with those deduced from purely field dependent specific heat experiments. With increasing hydrostatic pressure to ∼1 GPa, the −ΔSM and ΔTad, both show a significant enhancement of about 37% and 13%, respectively for 9 T field change in case of Tb3Co. On the other hand, Ho3Co exhibits a decrease of about 8% in both −ΔSM and ΔTad with increasing pressure. The refrigerant capacity (RC) also increases from 650 J kg−1 to 847 J kg−1 in the case of Tb3Co and it goes down from 665 J kg−1 to 615 J kg−1 for Ho3Co for an increase of pressure to 1 GPa. With increasing pressure, the peak widths of both −ΔSM and ΔTad increase in case of Tb3Co, although the increase is more in −ΔSM. However, such noticeable changes in peak widths with pressure were not observed in Ho3Co. At ambient pressure, peak of −ΔSM (−ΔSMpk) scales with (H/TN)2/3 for both the compounds, consistent with the prediction of mean field theory (MFT) for second order magnetic transition. However, deviation from MFT was noticed at high pressures as −ΔSMpk was found to scale with (H/TN)3/4 instead of (H/TN)2/3 for both the alloys. Further, normalised −ΔSM curves for different ΔH and pressures collapse on a single universal curve in both the compounds thereby indicating that the second order magnetic transition persists even up to ∼1 GPa pressure.