The influence of the Mn substitution by Fe atoms on the magnetocaloric and magnetic properties of the martensitic Ni50Mn36Sn14 Heusler-type compound has been investigated using magnetization measurements. The insertion of Fe atoms reduces the Mn-Mn AF interactions resulting in (i) a systematic decrease in the martensitic transition temperature, down to its disappearance at 15 at. % of Fe, (ii) an enhancement of the saturation magnetization, and (iii) a monotonic increase in the L21-type phase Curie temperature. The Fe substitution also induces metamagnetic transition from an incipient AF to a noncollinear spin configuration for applied magnetic fields higher than 3 T in the case of 3 and 7 at. % Fe substitutional. The exchange-bias effect is only found in compounds with a well-defined martensitic phase transition (Fe content lower than 10 at. %). The maximum of the inverse magnetic entropy change, for a field variation of 5 T, is about +12 J kg−1 K−1 and it is nearly constant for Fe content up to 7 at. %. This observation suggests that the Ni50(Mn1−xFex)36Sn14 Heusler-type compounds could be used to prepare composites with potential for technological application in magnetic refrigerators.

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Due to their brittleness, assembling of ceramics pieces is generally achieved through brazing but thermal stresses during cooling frequently induce cracking of the material used for brazing. In order to check if such damage is avoidable, it is necessary to characterize the brittle to ductile transition (BDT) of the material. Simple compression is not suited for crack studies, because of mixed loading (mode II + compressive mode I cracking). Another type of test, the cylinder splitting test, known as the Brazilian test, can be carried out by applying compressive forces on two opposite generatrix of a cylinder: this causes a uniform tensile stress on the plane containing the axis of the cylinder and the generatrix, leading to mode I cracking. The advantage of this test is to avoid expensive and random machining of brittle samples. This study shows that the Brazilian test is well adapted for the measurement of toughness and the characterization of the BDT of materials whose room temperature behaviour is brittle (silicides, intermetallics etc.).

The mechanosynthesis process has been applied in theLaFe11.4Si1.6 compound to reduce the undesirable segregated rich-Fe phases that impair its application as a solid magnetic refrigerant. The influence of La substitution (5 at. %) by Y or Gd atoms on the magnetic and magnetocaloric properties has been also studied. Y- and Gd-substituted compounds have a magnetic ordering temperature higher than the pure La compound. While the Y-substituted compound keeps a first-order-like magnetic transition feature, the Gd-substituted one seems to suppress it. The maximum value of the magnetic entropy change of the Y compound is roughly the same as the La compound (−18 J∕kg K) but with a magnetic entropy change peak significantly broader. For the Gd-compound case a drastic reduction of the magnetic entropy change (−7 J∕kg K) is found.