We report the discovery of CMA, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of $0.83,mathrm{mu_B}$/Mn, significantly reduced from the Hunds rule value, and the mag
netic entropy obtained from specific heat measurements is correspondingly small, only $approx 9$ % of $R mathrm{ln},2$. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility $chi$ is anisotropic below 20 K, with a maximum ratio of $chi_{[010]}/chi_{[001]}approx 3.5$. A strong power-law divergence $chi(T)sim T^{-1.2}$ below 20 K implies incipient ferromagnetic order, and an Arrott plot analysis of the magnetization suggests a vanishingly low Curie temperature $T_Csim 0$. Our experiments indicate that CMA~is a rare example of a Mn-based weak itinerant magnet that is poised on the verge of ferromagnetic order.
We report a combined experimental and theoretical investigation of the magnetic structure of the honeycomb lattice magnet Na$_2$IrO$_3$, a strong candidate for a realization of a gapless spin-liquid. Using resonant x-ray magnetic scattering at the Ir
L$_3$-edge, we find 3D long range antiferromagnetic order below T$_N$=13.3 K. From the azimuthal dependence of the magnetic Bragg peak, the ordered moment is determined to be predominantly along the {it a}-axis. Combining the experimental data with first principles calculations, we propose that the most likely spin structure is a novel zig-zag structure.
