In the magnetic materials utilized in storage devices, intrinsic crystalline anisotropies of matter were utilized. However, in recent 10 years, the interfacial anisotropies of the 2D magnetic layers became the most important characteristics in media of hard disk drives (HDD), and in magnetic random access memories (MRAM). In media of HDD, the interfacial anisotropy of ultrathin Cobalt alloy below 1.5nm deposited on the underlayer like MgO or Pt is one order higher than the intrinsic cobalt anisotropy (K~106 erg/cc), hence it can help to store a bit at a smaller size than the traditional media based on crystalline anisotropy. Furthermore, one ultrathin layer is not thick enough to overcome the superparamagnetic limit; thus, multilayers have to be utilized, and the design of anisotropy distribution in multilayers ensures the uniform switch of magnetization in a bit. For magnetic layers in MRAM, the CoFeB layer below 1.5nm developed on MgO underlayer is one of the key spintronic magnetic materials, which insures high magnetoresistance for the CoFeB/MgO/CoFeB structure; the role of defects is the key to understand magnetic properties of the CoFeB layer, and thus it is also important for the memory cell design.

1. Yi Wang, Dan Wei, Yi Wang, Xiufeng Han and Kai-Zhong Gao, “Micromagnetic Simulation of Co/Pt Multilayers with Perpendicular Anisotropy”,IEEE Trans. Magn., vol. 48, no. 11, pp.3438–3441, Nov. 2012

2. Yi Wang, Dan Wei, Kai-zhong Gao, Jiangwei Cao and Fulin Wei, “The Role of Inhomogeneity of Perpendicular Anisotropy in Magnetic Properties of Ultra Thin CoFeB Film”, J. Appl. Phys. 115, 053901 (2014)

3. Yi Wang, Lei Xu, Zhongshui Ma and Dan Wei, “Switching Current Dispersion in Magnetic Memory Bits Due to Inhomogeneity of Perpendicular Anisotropy”, IEEE Trans. Magn., vol. 50, no.11, 3400804, (2014)

4. Longze Wang, Jiangnan Li, Zhen Zhao, Dan Wei, and Kai-Zhong Gao, “Micromagnetics Studies of CoX/Pt Media With Interfacial Anisotropy Based on Polycrystalline Structure Model Using Voronoi Tessellation Method”, IEEE Trans. Magn., VOL. 51, NO. 11, 3202304, (2015)

5. Jiangnan Li, Zhen Zhao, Mengwei Zhang and Dan Wei, “Optimum Multilayer Anisotropy Distribution for Microwave-Assisted Magnetic Recording [CoX/Pt]n Media”, IEEE Trans. Magn., VOL. 52, NO. 7, 7100404, (2016)

6. Zhen Zhao, Jiangnan Li, Longze Wang, and Dan Wei, “Influence of exchange on signal-to-noise ratio in [CoX/Pt]4 media”, AIP Advances 7, 056515, (2017)