Analysis of the crystallographic and magnetic structures of the Tb<sub>0.1</sub>Pr<sub>0.9</sub>Al<sub>2</sub> and Tb<sub>0.25</sub>Pr<sub>0.75</sub>Al<sub>2</sub> magnetocaloric compounds by means of neutron scattering
Tedesco, Julio C. G.3; Carvalho, Alexandre Magnus G.4; Christensen, Niels Bech1; Kockelmann, Winfried5; Telling, Mark T. F.5; Yokaichiya, Fabiano6; Toebbens, Daniel M.6; Simeoni, Giovanna G.7; Cardoso, Lisandro P.8; Coelho, Adelino A.8; Bordallo, Heloisa N.3
1 Department of Physics, Technical University of Denmark2 Neutrons and X-rays for Materials Physics, Department of Physics, Technical University of Denmark3 University of Copenhagen4 Brazilian Synchrotron Light Laboratory5 Rutherford Appleton Laboratory6 Helmholtz–Zentrum Berlin für Materialien und Energie7 Technische Universität München8 State University of Campinas
Neutron powder diffraction and inelastic neutron scattering data were used to simulate and understand the magnetization and heat capacity curves of the pseudobinary Tbx Pr1-x Al2, with x = 0.10 and 0.25, as a function of temperature. From the Rietveld analysis, we concluded that no crystallographic transition occurs in these samples, and the high symmetry of the magnetic structure was confirmed. Moreover, the different contributions from the reflection planes could be related to the known exchange bias-like effect characteristic for the x = 0.25 sample, also suggesting the existence of some rearrangement of the magnetic moments or even the presence of spin frustration in this system. Finally, the obtained set of theoretical parameters using the mean field approach for the two systems consisting of two sublattices allowed the experimental data to be described and to explain their physical behaviors. The ensemble of our results leads us to affirm that the quadrupolar interactions as well as an existence of some rearrangement of the magnetic moments or a frustration play an important role in the strong unidirectional anisotropy and the exchange bias-like effect observed in this pseudobinary system.
Journal of Materials Science, 2015, Vol 50, Issue 7, p. 2884-2892