High coercivity characteristics of FePtB exchange-coupled nanocomposite thick film spring magnets produced by sputtering

Abstract Thick film magnets (∼3.2 μm) deposited on silicon substrate at processing temperatures lower than 400 °C, exhibiting high coercivity ( H c ∼ 604 kA m −1 ), high maximum energy product [( BH ) max = 95 kJ m −3 ] and good surface properties, were obtained by sputtering technique. The effects of sputtering power, substrate temperature ( T s ) and film thickness on the magnetic properties of the films were studied. Films exhibiting very good hard magnetic properties are mainly made up of nanosized hard (L1 0 -FePt) and soft (Fe 2 B and Fe 3 B) magnetic phases, which are exchange coupled. The exchange spring behavior in these films was investigated and a high recoil rate of more than 90% was obtained. The ability to deposit permanent magnet thick films exhibiting good hard magnetic as well as surface properties on silicon, as demonstrated in the present work, is very promising for the fabrication of micromagnets for magnetic MEMS.