Magnetocaloric effect of Er5Si4 under hydrostatic pressure

The magnetocaloric effect (MCE) of the compound Er5Si4 has been investigated as a function of the applied magnetic field (up to 50 kOe) and the hydrostatic pressure (from ambient pressure up to 9 kbar). At constant magnetic field change, increasing the pressure up to 1.4 kbar induces a global rise of the magnetic entropy change, parallel to Delta S-mag parallel to, with the peak at T-C congruent to 30 K growing from 14.9 to 20.1 J/kg K. Between 1.4 and 9 kbar, the size and shape of the parallel to Delta S-mag parallel to vs T curve remain nearly constant but the peak moves to higher temperatures and stabilizes above 3.5 kbar at T similar to 36 K. Contrary to many other R-5(SixGe1-x)(4) compounds, the magnetocaloric effect in Er5Si4 does not originate from the simultaneous field-induced magnetic and structural transformations since previous studies of the compound have demonstrated that moderate steady magnetic fields are not strong enough to induce the M -> O(I) transformation at the atmospheric pressure. However, the pressure dependence of the MCE is associated with pressure-induced M -> O(I) structural transformation that takes place in Er5Si4. The increase in the magnetic entropy change occurs because of a modification of the magnetic coupling derived from the differences in the interlayer bonding in the M and O(I) states. This gives rise to an enhancement of the ferromagnetic interactions in the O(I) phase with respect to the ambient pressure M state, resulting in a stronger saturation magnetization and a higher Curie temperature, i.e., T-C(M)=30 K and T-C(O(I))=36 K.