Anisotropic spin fluctuations in the itinerant-electron ferromagnet MnP

The paramagnetic scattering cross section of the anisotropic metallic ferromagnet MnP has been measured up to the zone boundaries along the [100] and [010] directions perpendicular to the easy magnetization axis. The spectral shape functions in both directions are well fitted to a Lorentzian form at T=T_C (290.5 K), 1.03T_C, and 1.20T_C except those close to the zone boundaries. Near T_C the linewidth along [010] follows the dynamical scaling prediction for the isotropic ferromagnet Γ(q)∝q^2.5. On the contrary, a unique q dependence, Γ(q)∝q^3.2, along [100] was observed. However, these q dependencies deviate at small q(q<0.1 A^-1 along [100] and q<0.02 A^-1 along [010]), suggesting the existence of a residual linewidth of Γ₀∼0.02 meV at q=0.