J. Ayres de Campos

A magnetization and neutron powder diffraction study of compounds (R = Y, Dy, Ho, Er)

Neutron powder diffraction experiments and magnetic measurements were performed on compounds of the series (R = Y, Dy, Ho and Er). The influence of the R element on both the structural and the magnetic properties of the different compounds is discussed, as well as the possible correlation between the iron environments and the local moments. Comparison is made with a previous Mossbauer study on the same compounds.

Magnetic phase transitions in RFe9.5Mo2.5 intermetallics studied by 57Fe Mössbauer spectroscopy, magnetisation and μ+SR

Abstract A series of RFe 12− x M x -type alloys were stabilised with M = Mo and x = 2.5 for R = Y, Nd, Dy and Er. Magnetisation, ac susceptibility measurements and μ + SR spectroscopy results are in good agreement with a systematic 57 Fe Mossbauer spectroscopy analysis. The strength of all local iron magnetic moments (and the related hyperfine fields), as well as the long range magnetic ordering, have been found to be markedly affected by the substitution of iron by molybdenum in Fe(8i) sites. It was found that the temperature dependence of the order/disorder phenomenology is well described by local magnetic correlation.

Study of RFe12 xMox (R = Y, Ho) compounds by neutron powder diffraction, ac susceptibility and magnetization

Neutron powder diffraction, magnetization and ac susceptibility measurements were performed on compounds of the series RFe12 x Mox (RD Y and Ho,xD 1, 2, 3). The influence of the Mo content on both structural and magnetic properties is discussed. Comparison with published data for different Mo concentrations is made. It is found that the effect of Mo substitution for Fe on structural and magnetic properties can be described by two regimes separated by a critical Mo content aroundxD 2.

Optics and children

Light and Optics are subjects that naturally attracts the interest and sympathy of children even from very early ages. In this communication, we present a serie of experiments and support material designed in this hands-on perspective, to be used to introduce the study of light and optics to kindergarten and early basic school students. Our hands-on investigative approach leads the students, aged 4 to 10 years, to observe the experiment and discover themselves, in a critical and active way, different aspects of light and optics. Preparing funny eye catching situations and experiments predispose the children to work, effectively, enjoying themselves while building up their self-confidence.