Magnetocaloric effect of Er5Si4 under hydrostatic pressure

TitleMagnetocaloric effect of Er5Si4 under hydrostatic pressure
Publication TypeJournal Article
Year of Publication2009
AuthorsArnold Z, Magen C, Morellon L, Algarabel PA, Kamarad J, Ibarra MR, Pecharsky VK, Gschneidner KA
Journal TitlePhysical Review B
Date Published04/28
ISBN Number1098-0121
Accession NumberISI:000265943200092
Keywordscurie temperature, entropy, erbium compounds, ferromagnetic materials, gd-5(si2ge2), high-pressure solid-state phase transformations, magnetisation, magnetocaloric effects, transition

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.

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