Large coercivity of 13 kOe in L1₀-ordered CoPt on Si/SiO₂ substrates by hydrogen annealing

Abstract

L10-ordered CoPt with a large coercivity (Hc) of 13 kOe was demonstrated on Si/SiO2 substrates by hydrogen annealing. Equiatomic 11.2-nm-thick (Co/Pt)4 multilayer thin films were fabricated by electron-beam evaporation and were annealed at 500–900 °C for 10–90 min under an Ar/H2 mixed gas atmosphere. The annealing temperature and time dependences of the crystal structures, magnetic properties, and surface morphologies of the films were systematically analyzed based on the experimental results obtained from grazing incidence X-ray diffraction, vibrating sample magnetometer, and scanning electron microscope, respectively. Hydrogen annealing effectively promoted the out-of-plane c-axis orientation of L10-CoPt compared to the vacuum annealing according to the GI-XRD patterns. A maximum Hc of 13.3 kOe was obtained in L10-ordered CoPt with angular-outlined isolated grains by hydrogen annealing at 800 °C for 60 min, where the c-axis of L10-ordered CoPt was randomly distributed.

Nanostructure-induced L10-ordering of twinned single-crystals in CoPt ferromagnetic nanowires

“…Therefore, the c and a values for the L1 0 -CoPt nanowires were determined to be c ¼ 3.6804 A and a ¼ 3.7799 A, respectively, which agrees with values in the literature. 32,[50][51][52]68,70,91 The magnetic hysteresis loops (M-H curves) of the nanowires aer annealing at 650 C for 90 min are shown in Fig. 4.…”

“…signal. 52 The lattice parameters (c and a) for L1 0 -CoPt were obtained from the superlattice peaks of L1 0 -CoPt 001 and 110, respectively. The diffraction peaks were assigned using the powder diffraction file (PDF) card (CoPt: 03-065-8969) and ref.…”

“…44 We also reported the L1 0 -ordering of Co/Pt multilayer thin lms on thermally oxidized Si (Si/SiO 2 ) substrates by EB evaporation and annealing processes, which was characterized by scanning electron microscope (SEM), grazing incidence X-ray diffraction (GI-XRD), and vibrating sample magnetometer (VSM). [50][51][52] In Pt (6.6 nm)/Co (4.8 nm) bilayer thin lms, graded lms consisting of L1 2 -ordered CoPt 3 , L1 0 -CoPt, and L1 2ordered Co 3 Pt were formed during interdiffusion of the bilayer annealed at 800 C for 30 s by RTA in a vacuum. 50 Because the interdiffusion and L1 0 -ordering of CoPt were in progress owing to the short annealing time of 30 s RTA process and both L1 2 -CoPt 3 and L1 2 -Co 3 Pt do not usually show large H c , an H c in the graded lms was as small as 2.1 kOe.…”

“…51 Moreover, we also showed that hydrogen annealing contributed to the enhanced H c of L1 0 -CoPt. 52 Aer annealing of the (Co/Pt) 4 multilayer thin lms at 800 C for 60 min, a maximum H c of 13.3 kOe was obtained in L1 0 -CoPt, which exhibited angular-outline isolated grain structures. 52 If the nanowires can be directly fabricated Si/SiO 2 substrates by rst using lithography and then L1 0 -ordering of initially disordered ferromagnetic lms by annealing, the etching process can be omitted, which leads direct fabrication process of spintronic devices on Si/SiO 2 substrates.…”

“…52 Aer annealing of the (Co/Pt) 4 multilayer thin lms at 800 C for 60 min, a maximum H c of 13.3 kOe was obtained in L1 0 -CoPt, which exhibited angular-outline isolated grain structures. 52 If the nanowires can be directly fabricated Si/SiO 2 substrates by rst using lithography and then L1 0 -ordering of initially disordered ferromagnetic lms by annealing, the etching process can be omitted, which leads direct fabrication process of spintronic devices on Si/SiO 2 substrates. Direct fabrication of L1 0 -CoPt nanowires on Si/SiO 2 substrates using only lithography and subsequent annealing can be benecial for the future integration of non-volatile spintronics with silicon-technologybased complementally metal-oxide semiconductor (CMOS) integrated circuits.…”