Microstructure evolution and magnetic properties of FeB/Pt multilayers and FeBPt composite films

Abstract

Comparisons of microstructural evolution and magnetic properties were made of a FeB12/Pt10/[FeB1.2/Pt1]15/Ta5 nm multilayered structure with a FeB12/Pt10/FeBPt33/Ta5 nm co-deposited structure. The Ta capping layer was used to protect the films from oxidation. Both these samples were sputtered in the same planetary deposition system onto thermally oxidized silicon substrates. They both represent layer-by-layer deposition, with the second type of deposition having atomically fine layers, more than an order of magnitude finer than the first type. The samples were annealed at a range of times, temperatures, and vacuum conditions. X-ray diffraction (XRD), transmission electron microscopy, and alternating gradient magnetometry were employed to characterize the structural and magnetic properties, respectively. Significant differences were observed between the two types of structures. A maximum coercivity of 8.9 kOe was seen for the atomically fine multilayer, about 10% more than that for the coarse multilayer. XRD analysis confirmed that both the coarse and fine multilayers were in the L10 phase after annealing. Our results indicate that the co-deposited film, which is really composed of atomically fine multilayers, is superior to the coarse multilayered FeB/Pt for the formation of L10-phase FePt.

(111) Orientation preferred L1 FePtB patterned by block copolymer templating

“…After annealing at 550 C for 30 min, the film showed a (111) peak shifted to a larger angle $41.1 accompanied by an increase in intensity, indicating the formation of (111) orientation preferred L1 0 structure. 19,21 Figure 1(b) shows M-H loops of the as-deposited and in situ annealed continuous FeB/Pt films. It can be seen clearly that the M-H loop becomes much broader with higher coercivity after in situ annealing, which also confirmed the occurrence of ordering.…”

“…The bottom layers of FeB 4/Pt 5 nm served as seed layers to promote the formation of the ordered structure. 21,22 An infrared lamp array was positioned in one of the target positions for in situ heating. The base pressure prior to deposition was 5 Â 10 À8 Torr and the Ar sputtering pressure was maintained at 2 mTorr.…”

“…The base pressure prior to deposition was 5 Â 10 À8 Torr and the Ar sputtering pressure was maintained at 2 mTorr. 21,23 Three-inch diameter high purity Fe 80 B 20 , Pt, and Ta targets were sputtered at powers ranging from 103 to 311 W, corresponding to deposition rates of 0.02-0.083 nm/s. FeB/Pt multilayered films were in situ lamp annealed at 550 C for 30 min.…”

“…It can be seen clearly that the M-H loop becomes much broader with higher coercivity after in situ annealing, which also confirmed the occurrence of ordering. 21 In order to pattern the FeBPt film, we employed the block copolymer templating method using PFS-b-PS. 24,25 After removing the PS matrix, Figure 2(a) shows a monolayer of PFS nanospheres with a diameter of about 20 nm, forming an etch mask.…”

“…20 In this paper, we deposited FeB/Pt multilayers and annealed them to form L1 0 structure FePt. 21 Then, we carried out a matrix study of patterning FeBPt over a range of etch conditions using block copolymer templating. The effects of etching and annealing will be discussed.…”