Insights on the origin of the Tb5Ge4 magnetocaloric effect

• Published in: Physica. B, Condensed matter Condensed matter, 2017-05, Vol.513 (C), p.72-76
• Main Authors: Belo, J.H., Barbosa, M.B., Pires, A.L., Costa, R.M., Teixeira, J.G.V., Silva, J., Algarabel, P.A., Magen, C., Morellon, L., Amaral, J.S., Zeitler, U., Veerendra, G., dos Santos, A.M., Ren, Y., Ibarra, M.R., Araújo, J.P., Pereira, A.M.
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Magnetic phase transitions; Magnetocaloric effect; Phase diagram; Structure of crystalline solids
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2017.03.009

In this report the magnetic, atomic structures and spin-lattice coupling have been thoroughly studied through high magnetic field magnetometry, Synchrotron X-ray diffraction under applied magnetic field and magnetostriction measurements in the Tb5Ge4 compounds. A field induced phase transition from an antiferromagnetic towards a ferromagnetic ordering was confirmed but with absence of structural transformation. This absence has been confirmed experimentally through synchrotron x-ray diffraction under applied field (up to 30T). Moreover, this absence was explained via a thermodynamic free energy model: first principles calculations determined a large energy gap (ΔE=0.65eV) between the two possible structures, O(I) and O(II). From magnetic and structural properties, a H-T phase diagram has been proposed for Tb5Ge4. Finally it was observed a large magnetostriction (up to 600ppm) induced by ∆H=7T.