\textbf{Magnetic properties of Cr}$_{\mathrm{\mathbf{3}}}$\textbf{Te}$_{\mathrm{\mathbf{4}}}$\textbf{ doped with transition metals: An }\textbf{\textit{ab intio}}\textbf{ study}

We report density functional theory (DFT) study of the magnetic properties of Cr$_{\mathrm{3}}$Te$_{\mathrm{4}}$ doped with transition metals (TM) (Co, Fe, Ni, V and Mn), TM ions doped in Cr sites, Cr$_{\mathrm{3-x}}$ (TM)$_{\mathrm{x}}$Te$_{\mathrm{4}}$ (x $=$ 0.5 and 1). We performed screening of the exchange coupling interaction and magnetization modifications upon the substitution of Cr by 3d-transition metals at various Cr sites in the Cr$_{\mathrm{3}}$Te$_{\mathrm{4\thinspace }}$structure. Our calculation show that Cr$_{\mathrm{3}}$Te$_{\mathrm{4}}$ has ferromagnetic coupling and large magnetization (Magnetization per unit cell is 18.24$\mu $B). Magnetocrystalline anisotropy (MAE) of this material is also large (MAE$=$ 1.67MJ/m$^{\mathrm{3}})$. Our calculations show that the increase in interlayer spacing strengthen ferromagnetism of Cr$_{\mathrm{3}}$Te$_{\mathrm{4}}$. Doping with Mn increases Cr$_{\mathrm{3}}$Te$_{\mathrm{4}}$ magnetization, but reduces the exchange coupling energy which means reducing Curie temperature (T$_{\mathrm{c}})$. We find that doping with 3d-TM elements decreases the magnetocrystalline anisotropy energies (MAE) of Cr$_{\mathrm{3}}$Te$_{\mathrm{4}}$.