Tuning magnetic properties in quasi-two-dimensional ferromagnetic Fe_{3− y} Ge_{1− x} As _x Te₂ (0  ⩽   x   ⩽  0.85)

We report that Fe₃GeTe₂ can form a wide solid solution by substitution of As for Ge, providing an opportunity to tune the magnetic and electronic properties in this 2D material. The crystal structure, physical properties and electronic structure of iron-deficient solid solution Fe_{3− y} Ge_{1− x} As _x Te₂ (0  ⩽   x   ⩽  0.85) are studied. We found that the Curie temperature can substantially change from 177 K to 33 K and resistivity decreases by about 30% with the arsenic doping x from 0 to 0.85. First principles calculations demonstrate that the elongation of Fe(1)–Fe(1) dumb-bells along c axis is essentially responsible for decreasing the integrated spin density of states below Fermi level and weakening spin polarization, resulting in a decrease of Curie temperature. Our study reveals the magnetism manipulation can be realized via modification of bondlengths in 2D magnetic materials. (paper)