magnetic nanoparticles are applicable in imaging , diagnosis , therapy , and biomaterial separation . the magnetic nanoparticles comprise a core represented as fe x m a v z y and a shell of an inner - transition element m b or the compound thereof , wherein m a is an inner - transition element , z is an element of the group vla , x is greater or equal to 0 , and v , y are positive numbers . the surface of the shell is optionally modified by liposome , polymer , aliphatic compound , aromatic compound or combinations thereof .