Strong Perpendicular Magnetic Anisotropy in CoFeB/Pd Multilayers

Abstract

The strong perpendicular magnetic anisotropy (PMA), indicated by a large coercivity of 590 Oe, is obtained in CoFeB/Pd multilayers through a systematic study that involves using various substrates (Si, glass, sapphire, and MgO) and seed layers (Al and Ta) and also varying the thickness of the seed layer. The PMA is nearly independent of the substrate when Al is used as a seed layer, but the dependence increases significantly with increasing seed layer thickness. The behavior becomes rather complicated for the multilayers with a Ta seed layer, showing a large substrate dependence and a large seed layer thickness dependence.

Variable variance Preisach model for multilayers with perpendicular magnetic anisotropy

“…However, once a certain threshold is overcome, the coercivity starts to decrease, in agreement with Jung et al [22] who found a constantH C for a range of small to mid n, and then a reducedH C for large n. To explain this effect, let us assume a perfect square hysteresis cycle with a coercive field given by the perpendicular anisotropy field given by (in Oe) H A ≡ 2K ⊥ /M s , where K ⊥ is the perpendicular anisotropy constant (in erg/cc), and M s is the saturation magnetization of the magnetic material (in emu/cc). Increasing n affects mostly the volume, and thus H A (and consequently H c ) remains constant.…”

“…3). This effect has been observed before experimentally and theoretically [21,22,25,53,68]. Knowing that the mechanism of reversal nucleation is identical for all the samples, namely the avalanche of labyrinth domain formation, the presence of a demagnetizing energy can be inferred.…”

“…Furthermore, PMA thin films are also of great interest for spin-torque oscillators due to the formation of dynamic droplet solitons [14][15][16][17] and their capabilities in generating zero field rf signals with increased output power [18][19][20]. Thus the importance of understanding the underlying physics related to PMA materials is clear, and many experimental and theoretical studies have been done on this topic [21][22][23][24][25].…”

Scaling of the anomalous Hall effect in perpendicular CoFeB/Pt multilayers

“…In fact, the extrinsic mechanism of SS and SJ results from the asymmetric impurity scattering caused by the SOI strength. 5,21 This is to say the strength of SOI in the [CoFeB/Pt] N multilayers is simply enhanced by the number of repeats, N. Moreover, the multiple domain structure has been found in the [CoFeB/Pt] N multilayer with large N, 13 which may be due to the increasing of roughness by the interdiffusion at the interface 14,22 or the change in the magnetostatic energy. 23 Our preliminary XRR results (not shown here) reveal that the interdiffusion (or the roughness at CoFeB/Pt interface) increases with N. Therefore, the enhancement of the scattering independent term (SS component) in AHE may be induced by the increase of strength of SOI due to the roughness.…”

Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

“…[2][3][4][5][6][7][8] However, the results in this article (and some recent papers) [26][27][28] have demonstrated that the structural condition is not a necessary criterion for the CoFeB/Pd interfaces. This is presumably a physically interesting aspect for a deep analysis of interfacial magnetic moment and electronic structure of the CoFeB/Pd interfaces by a number of tools, e.g.…”