One of the most important challenges in Nano-scale spintronics is the production of intrinsic two-dimensional ferromagnetic half-metals with large spin gaps and high Curie temperatures. Here, by using firs-principles calculation we predict two-dimensional transition metal hydrides MnHm (M: V, Cr, Fe, and Co) have different magnetic properties in various space groups. Our results show the magnetic ground state of VH3, FeH3 and CoH3 in space group P/4nmm, Cr2H3, Fe2H3 and Co2H3 in space group of P-3 m1 is ferromagnetic while V2H3 and CrH3 in space group of P-3 m1 and P/4nmm respectively, are antiferromagnetic. In particular Co2H3 monolayer is 100% spin polarized intrinsic ferromagnetic half metal with spin gap of 3.2 eV and Cr2H3 can also change to halfmetal by doping a small amount of electric charge with a band gap of 4.2 eV. The delocalized and unpaired d electrons around the Fermi level act as the chief source of magnetism and half metallicity. The Curie temperature, calculated utilizing the mean-field approximation, is 485 and 227 K for Co2H3 and Cr2H3 monolayers respectively so it can be concluded that Co2H3 and Cr2H3 monolayers are promising candidates for spintronic applications.
