K. Raj

Properties of Heusler-type materials Fe2TSi and FeCo2Si

Abstract A number of 3d, 4d and 5d elements are substituted into Fe3Si in an attempt to form Heusler-like alloys. It is found that with the heat treatment followed, only the 3d elements V, Mn and Co form Heusler alloys. Substitution of the other elements produces polyphase materials. For such elements the limits of solubility in Fe3Si are determined. For the Heusler alloys the data on degrees of disorder, hyperfine fields and magnetization are presented. These studies, in addition, test the already known site preferences of the transition metal impurities in Fe3Si at high impurity concentrations.

Temperature dependent splitting of the 59Co hyperfine field in GdCo2

Abstract We have studied the temperature dependence of the 59Co NMR in the magnetically ordered state in GdCo2 between 1.3 K and 335 K. A clearly resolved splitting in the 59Co spectrum is observed to occur at 200 K. This splitting is interpreted as due to a change in easy axis from [100] to a detection which is not a major symmetry axis. Furthermore, a sharp change in the intensity ratio of the two clearly resolved lines in the spectrum occurs at about 300 K.

Fe hyperfine fields in Fe3-xVxSi alloys

Abstract The Mossbauer spectra of Fe in Fe 3- x V x Si alloys for 0⩽ x ⩽1 shows that V occupies almost exclusively one of two Fe sites (the B site). As x increases the spectra of Fe on the other site (the A, C site) becomes increasingly complex as the number of their V 1st neighbors increases. Simulated Mossbauer spectra were calculated using moments obtained by a simple model from bulk magnetization and V NMR data. This model assumes a decrease in Fe(A, C) moments as the number of their Fe 1st neighbors decreases. Comparison of the Fe(B) field of the alloy with x =1 to that of the alloy with x =0 gives an estimated reduction in the on site 4s electron polarization of about 100 kOe or about 0.05 unpaired 4s electrons.

Abstract: Studies of selective site substitution and spin polarization in systems based on Fe3Si

Transition metal elements substituted into Fe3Si were found to preferentially select one of the two inequivalent Fe sites in the Fe3Si structure, according to their location in the periodic table; a similar pattern of site occupation is observed in the Heusler alloys. Examination of the electronegativity of the transition metal impurities shows that the Fe site with 8 Fe 1nn is preferred by the less electronegative substitutions.(AIP)

Hyperfine interactions and structural disorder of Fe3Si1-xAlx alloys

Spin echo, X-ray and magnetization measurements are performed on Fe3Si1-xAlx alloys for 0<x<0.25. The results are analysed by considering near neighbour environments for various sites.

Local configuration studies of ferromagnetic Co-Ga alloys using neutron scattering and spin-echo NMR☆

Abstract Neutron scattering and spin-echo NMR experiments are performed on several magnetically ordered Co-Ga, Co2Ga2−xVx and Co2Ga2−xCrx alloys to study the distribution of the magnetic moments and local environments.

Investigation of conduction electron polarization effects in Fe3Si based ternary systems

Spin‐echo spectra of transition elements in the ternary alloys Fe3−xTxSi where T=V and show clear satellite structure for small x. For these alloys, it is concluded that changes in the ’’4s’’ CEP alone produce the satellite structure. Studies made on some Fe3Si based quarternary alloys are consistent with the above conclusions.

Magnetization and neutron diffraction studies on Mn3Si

Bulk magnetization and neutron diffraction measurements on Mn3Si are reported. Preliminary conclusions indicate a complex magnetic structure at low temperatures. The influence of dilute iron substitution on the magnetic behavior of Mn3Si is discussed.

Abstract: Fe hyperfine fields in Fe3−xVxSi alloys

Measurement of the Mossbauer spectra of Fe in Fe3−xVxSi alloys for 0?x?1 at 4.2 K and room temperature show that the Fe (A, C) spectra become increasingly complex as x increases and then collapse into a single line at the highest concentration. Simulated spectra reflecting Fe (A, C) moment variations are compared with the actual spectra.(AIP)

Mössbauer and NMR Studies of Site Substitution and Magnetic Structure of Fe 3-x Mn x Si Alloys

The NMR measurements in Fe3−xMnxSi alloys show increasingly complex spectra for x > 0.75 due to overlapping signals from Fe, Si and Mn nuclei in various sites. Mossbauer experiments were undertaken to identify the Fe57 resonances. The combined NMR and Mossbauer results have been used to elucidate the site substitution and magnetic structure of these alloys for (0 < x < 1.75).