Resonance Studies in FerromagneticFe2B andFe2Zr

Abstract

The hyperfine magnetic fields and quadrupole interactions in ${\mathrm{Fe}}_{2}$B and ${\mathrm{Fe}}_{2}$Zr are explored by nuclear magnetic resonance and the M\ossbauer effect. The anisotropy found in the ${\mathrm{Fe}}_{2}$B M\ossbauer spectra can be interpreted as a superposition of hyperfine patterns arising from an anisotropic magnetic field and electric field gradient in combination with either two magnetically inequivalent Fe sites (such as was observed in ${\mathrm{Fe}}_{2}$Zr) or a two-dimensional distribution of magnetization directions. Assuming the former, the two magnetic fields are found to be 252\ifmmode\pm\else\textpm\fi{}2 and 244\ifmmode\pm\else\textpm\fi{}2 dT at $T=4.2$ K. The B resonance frequency in ${\mathrm{Fe}}_{2}$B shows a ${T}^{\frac{3}{2}}$ dependence with some low-temperature deviations which can be understood in terms of a gap arising from magnetocrystalline anisotropy and spin-wave demagnetization. We have extracted the constants of proportionality in the spin-wave approximation, $C$ (the coefficient of the ${T}^{\frac{3}{2}}$ term) and $D$ (the coefficient of the ${T}^{\frac{5}{2}}$ term). We find that $\frac{D}{C}=(1.0\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and that the gap temperature ${T}_{g}\ensuremath{\le}1$ K. The measured pressure variations $\frac{\ensuremath{\partial}\ensuremath{\nu}}{\ensuremath{\partial}P}$ of the $^{11}\mathrm{B}$ and $^{91}\mathrm{Zr}$ frequencies are, respectively, -21\ifmmode\pm\else\textpm\fi{}2 and 31\ifmmode\pm\else\textpm\fi{}2 Hz ${\mathrm{bar}}^{\ensuremath{-}1}$.