e., the vortex core. The in-plane magnetization direction around the vortex core can be clockwise or counterclockwise, and the vortex core can be directed upward or downward. Therefore, vortices exhibit four different magnetic states defined by their chirality and polarity, which makes two bits of information be stored simultaneously. Furthermore, the flux-closed configuration leads to negligible stray fields and thus can reduce the interelement interactions in densely packed arrays. Because magnetic vortices have potential applications in ultrahigh-density recording media [1], magnetic random access memories [2, 3], and spintronic logic devices [4], many methods are proposed to control

them efficiently exploiting, such as element shape deviating from symmetry [5–8], nonuniform external magnetic field [9–11], magnetostatic and exchange coupling PRN1371 solubility dmso between element layers [12–14], and electric field [15]. In the heterostructure of Savolitinib magnetic tunnel junctions, vortices can be introduced into the ferromagnetic (FM) layers.

Therefore, the vortex stability and the magnetization switching characteristics can affect the overall performance. An example is discussed in the vortex random access memory [16]. In this article, we report a combined effect of interlayer dipolar interaction and shape asymmetry on magnetic vortex states in the soft magnetic layer of a magnetic tunnel junction by micromagnetic simulations. The control of the vortex chirality and enhancement of the vortex range are found Smoothened simultaneously. Methods Ganetespib mouse The micromagnetic simulations were carried out using the LLG Micromagnetics Simulator software [17] on a single triple-layer dot, which is composed of a hard FM layer of Co with thickness of 3 nm and a soft FM layer of Fe with thickness of 21 nm separated by vacuum representing an insulating barrier of thickness

3 nm. The dot diameter is fixed at 80 nm and the simulation cell size is kept constant as 2 × 2 × 3 nm3. The anisotropy constants used are K u  = 4 × 106 erg/cm3 for Co with uniaxial structure where the easy axis (E A) direction can be varied in the layer plane, and zero for Fe assuming a polycrystalline microstructure. The choices of these magnetic materials and the geometrical parameters are based on the following considerations: (1) both the magnetic materials, Fe and Co involved here, are common and most frequently exploited in micromagnetic simulations and in experiments; (2) the magnetic anisotropy strength between Fe and Co is large enough in order to make the Co as the hard magnetic layer and the Fe as the soft magnetic layer; (3) the geometrical parameters are chosen as the optimum values to display the main conclusions more clearly and distinctly. The other magnetization parameters for Co (Fe) are the exchange constant A = 3.05 × 10-6 erg/cm (2.1 × 10-6 erg/cm) and saturation magnetization M S = 1,414 emu/cm3 (1,714 emu/cm3) [17]. The damping constant is taken to be 0.