Magnetic transition in nanocrystalline soft magnetic alloys analyzed via ac inductive techniques

The magnetic transition in a FeSiBCuNb nanocrystalline alloy, associated with the decoupling of ferromagnetic crystallites around the Curie point of the residual amorphous matrix, is analyzed in this work through the temperature dependence of the ac axial magnetic permeability and impedance of the samples. The temperature dependence of both complex magnitudes presents a maximum in the irreversible contribution at a certain transition temperature. While for low values of the exciting ac magnetic field the transition temperature lies below the Curie temperature of the amorphous phase, a shift above this Curie point is observed increasing the amplitude of the applied ac magnetic field. The detected field dependence is interpreted taking into account the ac nature of the inductive characterization techniques and the actual temperature dependence of the coercivity of the samples

Scaling of low field magnetoelastic hysteresis in antiferromegnetic Dy

[eng] We investigate reversible inverse magnetostriction in order to study scaling properties of magnetic hysteresis in the helical antiferromagnetic phase of polycrystalline Dy. We argue that the experimental method used is more sensitive than studies of conventional magnetic hysteresis. This advantage allows us to study hysteretic properties of antiferromagnetic Dy over the temperature ranges, not accessible previously. We introduce generalized coercivity of magnetoelastic hysteresis and show that it demonstrates, under different experimental protocols, the same exponents of scaling power laws in the ferro- and antiferromagnetic phases. The similarity of hindering mechanisms impeding the mobility of domain walls in antiferromagnetic and ferromagnetic phases is suggested as the reason of the observed universality of hysteresis scaling

Martensitic transformation in Cu-Al-Ni shape memory alloys obtained by ball milling

The most important disadvantage of Cu-Al-Ni shape memory alloys concerns their high brittleness. Previous works have allowed us to show that powder metallurgy is an excellent way to improve the thermomechanical behavior of these alloys. However, the powder metallurgy processing method still shows some drawbacks, which can be overcome if powders are mechanically milled before compacting. In this work we present the study of the martensitic transformation of the alloy in the different stages of the elaboration process in order to evidence the way to elaborate a final alloy with the desired transformation temperatures starting from a mixture of available powders of different compositions.Peer reviewe

Systematic study of the reordering process in FeAl alloys by neutron diffraction

In this work, the authors performed in situ neutron diffraction experiments in order to study the reordering process of deformed Fe70Al30 alloy at a continuous heating rate from room temperature up to 875 K. The results indicate that the reordering process takes place in two steps. First at around 450 K, a precipitation of the B2 phase occurs, and again at around 610 K. The changes in structure observed at around 450 K explain the decrease of the magnetism observed in the reordering of this alloy.Peer reviewe