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Title: Insights on the origin of the Tb5Ge4 magnetocaloric effect

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1397420
Grant/Contract Number:
155/94; PTDC/CTM/NAN/5414/2014; SFRH/BD/88440/2012; SFRH/BD/97591/2013; MAT2014- 51982-C2-R; C1-R; E26; AC02-06CH11357; NMA01-111
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physica. B, Condensed Matter
Additional Journal Information:
Journal Volume: 513; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-12-23 12:21:44; Journal ID: ISSN 0921-4526
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

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., and Pereira, A. M. Insights on the origin of the Tb5Ge4 magnetocaloric effect. Netherlands: N. p., 2017. Web. doi:10.1016/j.physb.2017.03.009.
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. Insights on the origin of the Tb5Ge4 magnetocaloric effect. Netherlands. doi:10.1016/j.physb.2017.03.009.
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., and Pereira, A. M. Mon . "Insights on the origin of the Tb5Ge4 magnetocaloric effect". Netherlands. doi:10.1016/j.physb.2017.03.009.
@article{osti_1397420,
title = {Insights on the origin of the Tb5Ge4 magnetocaloric effect},
author = {Belo, J. H. and Barbosa, M. B. and Pires, A. L. and Costa, R. M. and Teixeira, J. G. V. and Silva, J. and Algarabel, P. A. and Magen, C. and Morellon, L. and Amaral, J. S. and Zeitler, U. and Veerendra, G. and dos Santos, A. M. and Ren, Y. and Ibarra, M. R. and Araújo, J. P. and Pereira, A. M.},
abstractNote = {},
doi = {10.1016/j.physb.2017.03.009},
journal = {Physica. B, Condensed Matter},
number = C,
volume = 513,
place = {Netherlands},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.physb.2017.03.009

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  • 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 30 T). Moreover, this absence was explained via a thermodynamic free energy model: first principles calculations determined a large energy gap (ΔE=0.65 eV) between the two possible structures, O(I) and O(II). Frommore » magnetic and structural properties, a H-T phase diagram has been proposed for Tb5Ge4. Finally it was observed a large magnetostriction (up to 600 ppm) induced by ΔH=7 T.« less
  • The present pulsed high-magnetic-field study on Ni{sub 50}Mn{sub 35}In{sub 15} gives an extra insight into the thermodynamics of the martensitic transformation in Heusler shape-memory alloys. The transformation-entropy change, ΔS, was estimated from field-dependent magnetization experiments in pulsed high magnetic fields and by heat-capacity measurements in static fields. We found a decrease of ΔS with decreasing temperature. This behavior can be understood by considering the different signs of the lattice and magnetic contributions to the total entropy. Our results further imply that the magnetocaloric effect will decrease with decreasing temperature and, furthermore, the martensitic transition is not induced anymore by changingmore » the temperature in high magnetic fields.« less
  • Band structure calculations at the level of LMTO-ASA provide insight into the electronic structure of BaV{sub 10}O{sub 15} and the origin of the structural phase transition. A crystal orbital Hamiltonian population/integrated crystal orbital Hamiltonian population analysis provides evidence that the crystallographic phase transition is driven by V-V bond formation. As well, the energy bands near the Fermi level are very narrow, <1eV, consistent with the fact that the observed insulating behavior can be due to electron localization via either Mott-Hubbard correlation and/or Anderson disorder. The partial solid solution, BaV{sub 10-x}Ti{sub x}O{sub 15}, was examined to study the effect of Ti-dopingmore » at the V sites on the structure and electronic transport properties. In spite of the non-existence of 'BaTi{sub 10}O{sub 15}', the limiting x=8, as indicated by a monotonic increase in the cell volume and systematic changes in properties. This limit may be due to the difficulty of stabilizing Ti{sup 2+} in this structure. For x=0.5 both the first order structural phase transition and the magnetic transition at 40K are quenched. The samples obey the Curie-Weiss law to x=3 with nearly spin only effective moments along with {theta} values which range from -1090K (x=0.5) to -1629K (x=3). For x>3 a very large, {approx}2x10{sup -3}emu/mol, temperature independent (TIP) contribution dominates. Conductivity measurements on sintered, polycrystalline samples show semiconducting behavior for all compositions. Activation energies for Mott hopping derived from high temperature data range from {approx}0.1eV for x=0-1 and fall to a plateau of 0.06eV for x=3-7. Low temperature data for x=3, 5 and 7 show evidence for Mott variable range hoping (VRH) with a T1/4 law and in one case between 5 and 17K, a Efros-Shklovskii correlated hopping, T1/2 law, was seen, in sharp contrast to BaV{sub 10}O{sub 15} where only the E-S law was observed up to 75K. Seebeck coefficients are small (<35{mu}V/K), positive, roughly TIP and increase with increasing x up to x=5. This may point to a Heikes hopping of holes but a simple single carrier model is impossible. The compositions for x>3 are remarkable in that local moment behavior is lost, yet a metallic state is not reached. The failure of this system to be driven metallic even at such high doping levels is not fully understood but it seems clear that disorder induced carrier localization plays a major role.« less
  • Room temperature magnetic refrigeration is an energy saving and environmentally-friendly technology which has developed rapidly from a basic idea to prototype devices. The performance of magnetic refrigerators crucially depends on the magnetocaloric properties and the geometry of the employed refrigerants. Here we review the magnetocaloric properties of Heusler alloys and related compounds with a high surface to volume ratio such as films, ribbons and microwires, and compare them with their bulk counterparts.
  • The Ni{sub 44.1}Mn{sub 44.2}Sn{sub 11.7} ribbons were prepared by melt spinning. A single-phase austenite with L2{sub 1} structure was confirmed in the melt-spun ribbons at room temperature. After the heat treatment, the martensitic transformation temperature increases obviously in the annealed ribbons. This method may be an effective way to tune the characteristic temperatures in the ferromagnetic shape memory alloys. Giant magnetic entropy changes are observed in the annealed ribbons. The peak values at 10 kOe are 32.1 and 20.1 J/kg K, for the ribbons annealed at 1123 and 1173 K, respectively.