Non-Fermi Liquid behavior in Itinerant Ferromagnet, HfMnGa$_2$

Single crystals of HfMnGa$_2$, space group Pnma, were grown using a Ga self flux technique. A sharp peak in the AC susceptibility $\chi_{AC}$ shows a phase transition at $T_C\approx26 K$, followed by Curie-Weiss behavior at higher temperatures. Arrott plot analysis confirms this transition is ferromagnetic with a spontaneous moment of $\mu_0\cong0.3 \mu_B/ $Mn. HfMnGa$_2$ has a coercive field of $\sim$ 0.1 T as well as a large magnetic anisotropy that restricts the moments to point in the [010] direction. Both a large Rhodes-Wohlfarth parameter $\mu_{\mbox{fluct}}/\mu_0\cong3.6$ and low T$_C$ suggest HfMnGa$_2$ is comparable to other itinerant ferromagnets MnSi, ZrZn$_2$ and Ni$_3$Al. Resistivity $\rho(T)$ shows HfMnGa$_2$ to be metallic with $\rho(T)-\rho_0$ having a $T^{5/3}$ dependance in the ordered state. This non-Fermi liquid relationship was also observed in Ni$_3$Al and ZrZn$_2$ over a more limited range of temperatures.