[en] Magnetic refrigeration has been seeing as a promising technology based on the magnetocaloric effect. One of its great advantages is it offers smaller global environmental impact relating to conventional refrigeration. Modeling and simulation of such processes can provide important data in the development and optimization of the experimental devices. Among existing designs, the rotary refrigerators presents several challenges in terms of complexity when comparing to reciprocating ones, which is compensated by several properties. A novel full process simulator of a magnetocaloric refrigerator processes was implemented to study the processes performance over different conditions. A stepwise modeling approach was applied, simplifying the phenomena of heat transfers. Gd was chosen as refrigerant material because of its magnetic transition temperature. The routine considered a rotating clockwise Gd wheel with an anticlockwise closed flow loop of water, which percolates the six Gd porous beds, hot and cold heat exchanger. The simulator was able to represent the transient aspects as well as the steady state conditions of the processes, considering both time performance and numerical stability. The inversion in heat transfer profiles along the process was used as a limit in the calculation of the maximum heat transfer absorption in the cold exchanger. (paper)

[en] The photothermally modulated magnetic resonance (PM-MR) technique was used to study thin films of Gd grown on fused quartz substrates. With this technique it was possible to observe the magnetic phase transitions for samples with different thickness and thermal treatments. Results were correlated with both magnetization and ESR measurements. The effect of the stress induced by the substrate was clearly observed through peak of the PM-MR signal.

[en] Fe₂MnSi fails to follow the Slater–Pauling rule. This phenomenon is thought to originate from either: (i) an antiferromagnetic arrangement of Mn ions at low temperature and/or (ii) chemical disorder. An important insight on this issue could be achieved by considering Fe₂MnSi_1−x Ga_x compounds, thoroughly studied here by means of magnetization, neutron diffraction and density functional calculations (DFT). Our results indicate that chemical disorder (and not the antiferromagnetic arrangement) is responsible for the deviation of the Slater–Pauling rule on Fe₂MnSi-based Heusler alloys. Furthermore, evidences suggest that Ga substitution into Si site favors the Fe/Mn disorder, further enhancing the observed deviation. (paper)