The magneto-mechano-chemical synthesis (1) is accompanied by splitting of electron energy levels (SEELs) and electron transfer in magnetic field (2) from nanoparticles Fe3O4 to doxorubicin. The concentration of paramagnetic centers (free radicals) is increased in the magneto-sensitive complex (MNC) (3). The local combined action of constant magnetic and electromagnetic fields and MNC in tumor (4) initiated SEELs, free radicals, leading to oxidative stress and electron and proton transport deregulation in the mitochondrion (5). Magnetic nanotherapy has more effectively inhibited the synthesis of ATP in mitochondria of tumor cell and induced the death of tumor cells compared to conventional doxorubicin.