Magnetic entropy change in bulk nanocrystalline Gd metals

Abstract

The magnetocaloric properties of the asconsolidated nanocrystalline and coarse-grained gadolinium metals were studied in the present work. With the decrease of Gd grains from micrometer to nanometer range, magnetic entropy change drops surprising from 10.07 to 4.47 J kg -1 K -1 at a magnetic-field change of 5 T, and their resultant magnetic entropy change uniformly peaks at 294, 290, and 288 K, respectively, corresponding to the magnetic transition temperature of the three samples. The Curie temperature T C of the nanocrystalline Gd shifts by more than 6 K below that of coarse-grained Gd sample. However, the values of magnetic entropy change of the nanocrystalline metals exhibit a more constant tendency compared with the coarse-grained sample. The Arrott plots indicate the second-order character of magnetic phase transition still in the nanocrystalline Gd metals. The refrigerant capacity calculated is also used to evaluate material refrigeration capacity.

Gd90Co2.5Fe7.5 alloy displaying enhanced magnetocaloric properties

“…On the other hand, below 293 K, this difference is reversed, with the MCE values for the alloy being smaller than those for polycrystalline Gd, with the difference becoming smaller with decreasing temperature. For the case of polycrystalline Gd, the MCE value for DH = 4000 kA/m (5 T) is consistent with the literature results [10][11][12].…”

Iron Oxide-based Magnetic Nanoparticles for High Temperature Span Magnetocaloric Applications

“…The RCP can be evaluated as the product of maximum entropy change and the temperature at full width of half maximum nanoparticles (~174 J-Kg -1 ) is larger than that of the RCP of 15 nm size Gd nanoparticles (~140 J-Kg -1 ). 12 Gd is usually used as the benchmark reference material for MCE. The stability of nanoparticles in a fluid is very important for self pumping cooling applications.…”

Magnetocaloric effect in high Gd content Gd-Fe-Al based amorphous/nanocrystalline systems with enhanced Curie temperature and refrigeration capacity

“…It was reported that with the decrease of Gd grains from micrometer to nanometer range, magnetic entropy change drops surprising from 10.07 to 4.47 J kg −1 K −1 . 24 Here, the average size of Gd 3 Al 2 and Gd in x = 80 is about 20 nm, and the size of Gd in x = 90 is about 28 nm. Therefore, the nano-sized Gd has a smaller ∆S M compared to that of bulk Gd.…”