Resonance Studies in FerromagneticFe2B andFe2Zr

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 Mössbauer effect. The anisotropy found in the ${\mathrm{Fe}}_2$B Mössbauer 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±2 and 244±2 dT at $T=4.2\mathrm{}$ 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 $\frac{D}{C}=(1.0\mathrm{}\pm 0.4)\times {10}^{-3\mathrm{}}$ and that the gap temperature $T_g\le 1$ K. The measured pressure variations $\frac{\partial \nu }{\partial P}$ of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}$ frequencies are, respectively, -21±2 and 31±2 Hz ${\mathrm{bar}}^{-1\mathrm{}}$.