Transition metal induced magnetism in smaller fullerenes (Cn for n ≤ 36)

The magnetic properties of 3d transition metals (TM) encapsulated inside smaller fullerenes ranging from C-20 to C-36 have been investigated using spin polarized density functional theory. The TM impurities stabilize asymmetrically at an off-center position for n >= 28. The total magnetic moment (MM) of TM@C-n complexes are largely contributed by TMs and a small amount of MM of 0.12-0.50 mu(B) is induced on the cage carbon atoms. The 3d TM atoms interact with C atoms of C-20 and C-28 cage ferromagnetically (FM) except for Ni@C-28 which shows antiferromagnetic (AFM) interaction. The magnetic interactions change from FM to AFM in C-32 cage for Ti, V, Cr and Mn. The MM gets quenched in Ni@C-n for n >= 32. The total MM of Mn@C-n does not show any change although the nature of magnetic interactions changes from FM to AFM at n = 32. Ti and V are the only TMs which show positive cohesive energy in all fullerenes considered. The smallest fullerene which can encapsulate all 3d TM are C-n for n >= 32, consistent with available experimental and theoretical results.