Exchange-coupled FePtB nano-composite hard magnets produced by pulsed laser deposition

Nano-composite FePtB thin films were deposited on naturally oxidized (1 0 0) silicon (Si) and glass (SiO2) substrates by using a pulsed laser deposition (PLD) technique. Effects of processing conditions on structural, surface and magnetic properties of the films were examined. Growth temperature (Ts) and the type of substrate (Si or SiO2) are shown to affect crystal structure and magnetic properties of FePtB thin films significantly. Under optimized processing conditions, a ∼1.7 μm thick FePtB film deposited on a glass substrate exhibits high coercivity (∼7.7 kOe), high reduced remanence [(Mr/Ms) ∼ 0.9] and high energy product (BH)max = 71 kJ/m3. The films exhibiting good hard magnetic properties are mainly made-up of nano-sized hard (L10-FePt) and soft (iron-boride) magnetic phases, which are shown to be exchange coupled. Fabrication of hard magnetic thin films by a simple and fast technique such as PLD is very promising for the production of micro magnets for MEMS applications.