Magnetic properties and microstructure of FePt/Ag2Te particulate films

The [FePt(1 nm)/X(t)](10) (X=Ag2Te, Ag, and thickness of t=0.1-0.3 nm) multilayer was deposited alternately on glass substrate and subsequently annealed by rapid thermal process (RTP) at 800 degrees C for 10 min. After RTP, the interface between FePt and Ag2Te was intermixed by forming particulate films. The L1(0) FePt grain size decreases from 18 to 13 nm as t of Ag2Te intermediate layer increases from 0.1 to 0.2 nm. The (FePt/Ag2Te)(10) particulate film shows perpendicular magnetization and out-of-plane coercivity increases with original Ag2Te thickness. As compared with (FePt/Ag2Te)(10), the (FePt/Ag)(10) multilayer is a continuous film after RTP. The Ag layer reduces ordering temperature of FePt but facilitates its grain growth during RTP. The [FePt/Ag(0.3 nm)](10) multilayer is magnetically isotropic as evidenced from magnetic hysteresis loops. Both Ag2Te and Ag atoms were immiscible with FePt phase but the FePt grains are refined and well-separated by Ag2Te phase. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3337641

Magnetic properties and microstructure of Ag2Se/FePt particulate films

Multilayer Ag/[Ag2Se(t)/FePt(1nm)](10) (thickness t = 0.1-0.4 nm) were alternately deposited on a glass substrate and subsequently annealed by rapid thermal process (RTP) at 800 degrees C for 3 min. After RTP, the interface between FePt and Ag2Se was intermixed to form particulate films. The grains size of the L1(0) FePt decreased from 9.8 to 7.7 nm when the total thickness of Ag2Se intermediate layer increases to 1 nm. The Ag/(Ag2Se/FePt)(10) particulate film showed perpendicular magnetization and a slight increase in out-of-plane coercivity over that of the original thickness of Ag2Se. The Ag2Se atoms were immiscible with FePt phase but the FePt grains were refined and separated well from the Ag2Se phase. Compared with Ag/FePt bilayer, the grains of the FePt were refined and uniformly separated in the Ag/[Ag2Se(t)/FePt](10) multilayer with t = 0.1 nm. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3553943

The Ag effect on magnetic properties and microstructure of FePt/Ag2Te particulate films

A [EFePt (1 nm)/Ag2Te(t)](10) (thickness t = 0.1-0.3 nm) multilayer was deposited alternately on glass substrate and subsequently annealed by a rapid thermal process (RTP). After the RTP, the interface between FePt and Ag2Te was intermixed, forming particulate films. The L1(0) FePt grain size decreases from 23 to 14 nm as t of the Ag2Te intermediate layer increases from 0.1 to 0.3 nm. The (FePt/Ag2Te)(10) particulate film shows perpendicular magnetization. Compared to (FePt/Ag2Te)(10), the Ag/(FePt/Ag2Te)(10)/Ag multilayer also shows perpendicular magnetization with less c-axis dispersion. The Ag capping and seed layers reduce the ordering temperature of FePt but facilitate its grain growth during RTP. As a result, the FePt grains are refined and well-separated by the Ag2Te phase, but change to a continuous film after inserting Ag capping and seed layers. (C) 2010 Elsevier B.V. All rights reserved

Magnetic properties and microstructure of (001) oriented Ag/FePt, Ag/FePt/Ag films

This study fabricates FePt film with (001) preferred orientation on a glass substrate by rapid thermal annealing (RTA) at 800 degrees C for 5 min. The ultrathin Ag capped layer and seed layer were inserted to reduce the ordering temperature. The (001) preferred orientation formed in Ag/FePt bilayer or Ag/FePt/Ag trilayer when annealed at 700 C for 5 min. From transmission electron microscopy (TEM) images, the interface Ag atoms diffused and segregated to form the Ag phase with L1(0) lattice, creating vacancies at the FePt lattice. The phase transformation activation energy was reduced as compared to single layer FePt film. Phase transformation strain dominated during ordering and grain growth. The formation of (001) preferred orientation on glass substrate was achieved by rapid ordering and recrystallization during post annealing. (C) 2009 Elsevier B.V. All rights reserved

Magnetic properties and microstructure of graded Fe/FePt films

A soft/hard Fe/FePt bilayer with perpendicular magnetization was prepared on a glass substrate. Annealed Fe/FePt film allowed modification of the Fe/FePt sharp interface to Fe/(Fe-rich FePt)/FePt graded interface with rigid magnetization due to the nanoscale soft/hard interface coupling. The magnetization was reversed at a single switching field and interpreted by the two-spin model. When the annealed temperature of the Fe/FePt film increased, the remanence magnetization decreased continuously but the out-of-plane coercivity increased obviously at 600-700 degrees C which was interpreted by the graded magnetic anisotropy. The coercivity can be tuning in the exchange coupled composite film. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3446198

Magnetization reversal process in Fe/FePt films

A soft/hard Fe/FePt bilayer with perpendicular magnetization was prepared on a glass substrate. Controlling the Fe layer thickness allowed modification of the hysteresis loops from rigid magnet with perpendicular magnetization to exchange-spring like magnet with parallel magnetization due to the nanoscale soft/hard interface coupling. For rigid magnetic films, the magnetization was reversed at a single switching field and interpreted by the two-spin model. In an exchange-spring like film, the in-plane magnetization reversal process was in two-steps and resulted from domain wall nucleation and propagation from the Fe layer into the FePt layer

Coercivity variation in exchange-coupled Fe/FePt bilayer with perpendicular magnetization

The soft/hard Fe/FePt film with perpendicular magnetization has been deposited on a glass substrate. The (001) oriented L1(0) FePt film was obtained when annealed by rapid thermal process at 800 degrees C and a Fe layer was deposited at room temperature with thicknesses of 2 rim to 20 rim. Controlling the Fe layer thickness allowed modification of the hysteresis loops from out-of-plane rigid magnet to in-plane exchange-spring like magnet due to the nanometer scale interface coupling. When the Fe layer thickness increased to 2 nm, the out-of-plane coercivity is reduced to 5.9 kOe but the remanence ratio (0.98) is still high. The Fe (2 nm)/FePt film shows perpendicular magnetization with linear in-plane hysteresis loop. The remanence ratio is reduced to 0.85 when the Fe layer thickness increased to 5 rim. When the Fe layer thickness was varied up to 10-20 rim, the in-plane hysteresis loop shows exchange-spring like behavior with two-step magnetization reversal processes. The films with perpendicular coercivity were moderated by the thickness of soft magnetic layer. (C) 2010 Elsevier B.V. All rights reserved