Bao-He Li

Magnetic properties and microstructure of FePt/Au multilayers with high perpendicular magnetocrystalline anisotropy

FePt/Au multilayers were deposited on preheated 100u2009°C MgO (001) single crystal substrates by magnetron sputtering. Magnetic properties and microstructure of the films were studied. Results show that the film possesses high coercivity HC, excellent perpendicular magnetic anisotropy (PMA), and weak interparticle exchange coupling (IEC) after annealing. FePt and Au can grow epitaxially on MgO substrates along the [001] direction, leading to excellent PMA. Au atoms partly diffuse to the boundaries of FePt phases and function as grain refiners and particle isolators, which markedly decrease the FePt grain size and IEC. Moreover, the additional FePt/Au interface energy, the stress energy due to the mismatch between FePt and Au lattices, and the diffusion of Au atoms all promote the ordering process of FePt film. This leads to the decrease in ordering temperature by 150u2009°C and a considerable increase in HC.

Low-temperature ordering and enhanced coercivity of L10-FePt thin film promoted by a Bi underlayer

We have studied L10-FePt thin films with a Bi underlayer. Experimental results show that the ordering temperature of the L10-FePt film can be lowered down to 300–350°C and the in-plane coercivity HC of the film is obviously enhanced by introduction of a Bi underlayer. After annealing at 400°C for 20min, a Bi∕FePt film realizes a HC of 13.5kOe and the ratio of the remnant magnetization Mr to the saturation one MS of as high as 0.93. The reduction of the ordering temperature and the enhanced magnetic properties of L10-FePt films can be understood by considering the large diffusivities of Fe and Pt associated with Bi diffusion.

Magnetic properties and microstructure of FePt∕BN nanocomposite films with perpendicular magnetic anisotropy

We have prepared L10-FePt∕BN nanocomposite films by depositing the FePt∕BN mutilayers on the MgO(100) substrates using magnetron sputtering followed by a postannealing process. We found the excellent perpendicular magnetic anisotropy of [FePt(2nm)∕BN(0.5nm)]10 film after annealing at 700°C for 1h x-ray diffraction patterns also indicate an excellent (001) texture of the film. This film shows a perpendicular coercivity of 7.48kOe and the ratio of the remnant magnetization Mr to the saturation one MS of as high as 0.93. We also found the good epitaxial growth of FePt grains on the MgO(100) substrate by cross-section high resolution transmitting microscopy.

Improvement of magnetic property of L10‐FePt film by FePt∕Au multilayer structure

We have prepared L10‐FePt films by sputtering FePt∕Au mutilayers on glass substrates followed by a vacuum annealing process. The magnetic measurement and x-ray diffraction indicate that the ordering temperature of the FePt films is reduced to 350°C and the coercivity (HC) is greatly enhanced by using the FePt∕Au multilayer structure. The interface energy and the stress energy due to the misfit between FePt and Au crystal lattices provide extra driving force to the ordering process of FePt films. Additionally, partial Au atoms are supposed to diffuse to the FePt grain boundaries during annealing, which consequently pins the magnetic domain wall and leads to the high HC.We have prepared L10‐FePt films by sputtering FePt∕Au mutilayers on glass substrates followed by a vacuum annealing process. The magnetic measurement and x-ray diffraction indicate that the ordering temperature of the FePt films is reduced to 350°C and the coercivity (HC) is greatly enhanced by using the FePt∕Au multilayer structure. The interface energy and the stress energy due to the misfit between FePt and Au crystal lattices provide extra driving force to the ordering process of FePt films. Additionally, partial Au atoms are supposed to diffuse to the FePt grain boundaries during annealing, which consequently pins the magnetic domain wall and leads to the high HC.

Effect of composition on L10 ordering in FePt and FePtCu thin films

FePt and FePtCu thin films with a fixed thickness of 50 nm have been prepared by magnetron sputtering. The atomic ratio of Fe to Pt atoms was accurately controlled by dc co-sputtering. After vacuum annealing for 20 min at 350 °C, a coercive force of about 605 kA m−1 is obtained in the Fe52Pt48 thin films with an ordering parameter around 0.87. The ordering parameter of the L10 phase is not enhanced by the addition of Cu to Fe52Pt48 films. On the contrary, the ordering process is improved by the addition of Cu to the Pt-rich or stoichiometric thin films. To keep the ordering of FePt films at a low annealing temperature, the lower the Fe content, the more addition of Cu is needed. It is found that the L10 phase can be obtained after annealing at 350 °C for 20 min only for films with the ratio of (FeCu) to Pt being in the range of 1.1–1.2.

Erratum: “Magnetic properties and microstructure of FePt/Au multilayers with high perpendicular magnetocrystalline anisotropy” [Appl. Phys. Lett. 93, 152513 (2008)]

with high perpendicular magnetocrystalline anisotropy” †Appl. Phys. Lett. 93, 152513 „2008...‡ Chun Feng, Qian Zhan, Baohe Li, Jiao Teng, Minghua Li, Yong Jiang, and Guanghua Yu Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083, People’s Republic of China Received 11 November 2008; accepted 14 November 2008; published online 30 December 2008 DOI: 10.1063/1.3041635