Spin- and charge-density waves around Ru impurities in $\alpha \text{−}\mathrm{Fe}$ alloys studied by ${}^{57}\mathrm{Fe}$ Mössbauer spectroscopy

A random solid solution of ruthenium in the $\alpha$-iron has been investigated by means of the Mössbauer spectroscopy using $14.4\mathrm{keV}$ transition in ${}^{57}\mathrm{Fe}$. Measurements were performed at room temperature versus ruthenium concentration varying up to about $12\mathrm{at.}\%$. Contributions to the iron hyperfine magnetic field and isomer shift due to the ruthenium impurity located at various distances from the resonant iron atom were determined. It was found that these contributions vary in sign depending upon the actual distance from the iron atom. The nearest neighbor ruthenium atom contributes $-1.99\mathrm{T}$. On the other hand, the second neighbor contributes $-0.09\mathrm{T}$, while the third neighbor contributes $+0.52\mathrm{T}$. Corresponding contributions to the isomer shift are as follows: $-0.019$, $+0.072$, and $+0.005\mathrm{mm}∕\mathrm{s}$. The above behavior is a strong indication for the presence of the spin and charge density waves in the vicinity of the ruthenium impurity in the $\alpha$-iron.

Figure 1

Mössbauer spectra for various ruthenium concentrations plotted versus absolute velocity. The solid line represents fit to the $\sigma =3$ model.

Figure 2

The most relevant model parameters plotted versus ruthenium concentration.

Figure 3

Hyperfine field distributions are plotted for various ruthenium concentrations and compared with the distributions obtained by the Hesse-Rübartsch method.

Figure 4

Electron spin density perturbation due to the ruthenium impurity and corresponding electron density perturbation plotted versus relative distance from the mean position of the impurity. Data were averaged over all nonzero ruthenium concentrations investigated.