Magnetic and magnetocaloric properties of Gd3-xTbxGa5O12 (x=0, 1, 2, 3) garnets

The structure and magnetocaloric properties of Tb substituted Gd3Ga5O12 garnets have been investigated. The structural refinement of X-ray diffraction patterns show that Gd3-xTbxGa5O12 (x=0, 1, 2,3) are isostructural, with the symmetry of a cubic space group la (3) over bard. The temperature dependence of magnetization studies indicate that all the samples follow Curie-Weiss paramagnetic behavior above 25 K and the effective magnetic moment increases with Tb concentration. The low temperature magnetization studies suggest that there exists a field dependent antiferromagnetic ordering of rare earth ions in Tb substituted Gd3Ga5O12, which in turn leads to a lower magnetic moment in Gd3-xTbxGa5O12 (x=1, 2, 3), compared to that of Gd3Ga5O12. Magnitude of field corresponding to the antiferromagnetic ordering is found to be dependent on temperature as well as on Tb concentration. Magnetocaloric effect analysis confirms that Tb substitution enhances the magnetic entropy change at higher temperatures and Gd3-xTbxGa5O12 (x=1, 2, 3) are better candidates than Gd3Ga5O12 for low fields and low temperature magnetic refrigeration applications. (C) 2012 Elsevier B.V. All rights reserved