Abnormal effect of substrate temperature on perpendicular magnetic anisotropy in sputter-deposited NdFeCo films on silicon substrates

• NdFeCo films were deposited on Si substrate at 25 and 310 °C, respectively.
• The films deposited at 310 °C show a large perpendicular magnetic anisotropy (PMA).
• The films deposited at 25 °C have an in-plane dominated anisotropy.
• The PMA is mainly from the magnetoelastic anisotropy induced by interfacial stress.

The effect of substrate temperature on the perpendicular magnetic anisotropy (PMA) in sputtered NdFeCo films on Si(111) has been studied. A strong PMA is observed in the NdFeCo films deposited at 310 °C, while the room temperature (RT) deposited films show an in-plane dominated anisotropy. The microstructure reveals a stratified microstructure along film thickness due to diffusion occurring at Si(111)/NdFeCo interface of the films deposited at 310 °C. Nd2(FeCo)17 nano-crystals and Nd2(FeCo)14Si3 and/or Nd6(FeCo)13Si intermetallic compounds in nano-size appear in the films deposited at 310 °C, while the RT deposited NdFeCo films are in amorphous state. Annealing at 300 °C results in atomic relaxation and thus ordering of the stripe domains. The distinguishing dependence of the micro/magnetic structure and magnetic characteristics of the NdFeCo films on substrate temperature and annealing temperature is presented. It is concluded that the strong PMA is mainly from the magnetoelastic anisotropy caused by the induced interfacial stress due to the opposite thermal expansion behavior between the NdFeCo layer and Si-doped interfacial layer.