Enhancement the perpendicular magnetic anisotropy of nanopatterned hard/soft bilayer magnetic antidot arrays for spintronic application

Abstract

Development of perpendicular magnetic anisotropy (PMA) thin films is a requisite for many applications. In this work, we have illustrated the enhancement of the PMA of Hard (Co)/ Soft (Permalloy, Py) ferromagnetic bilayers by depositing them onto nanoporous anodic alumina membranes with different hole diameters varying in the range between 30 nm and 95 nm. A dramatic change in the hysteresis loops behaviour with hole size, D, and magnetic surface cover ratio parameters has been observed: (1) for samples with small antidot hole diameters, the in-plane (INP) hysteresis loops show single-step magnetic behaviour; (2) for D = 75 nm, the hysteresis loops of Co/Py and Py samples exhibit a multistep magnetic behaviour; (3) a decreasing coercivity in the INP hysteresis loops for antidot arrays samples with D > 75 nm has been detected as a consequence of the reduction of the in-plane magnetic anisotropy and the rising of the out-of-plane component. A crossover of magnetic anisotropy from the in-plane to out-of-plane for bilayer antidot samples has been observed for Co/Py ferromagnetic bilayers, favoured by the interfacial exchange coupling between the two ferromagnetic materials. These findings can be of high interest for the development of novel magnetic sensors and for perpendicular-magnetic recording patterned media based on template-assisted deposition techniques.

Dependence of the Magnetization Process on the Thickness of Fe70Pd30 Nanostructured Thin Film

“…A magnetic anisotropy with an in-plane easy magnetization direction was obtained for the Fe 70 Pd 30 antidot arrays (see Figure 3b). Apart from the causes outlined for the continuous thin films, nanoholes induce a strong local shape anisotropy that tends to align the magnetization parallel to their edges [19,35]. Consequently, domain wall displacements result in the in-plane magnetization process, leading to hysteresis loops with a high squareness ratio [26].…”

“…For such applications, tailoring the direction and strength of the magnetic anisotropy, especially for the thermal stability and switching reliability of magnetic bits, is a crucial prerequisite [15]. In this regard, the existence of ordered arrays of nanoholes (i.e., antidot arrays) induces a demagnetization field distribution around the holes that can completely alter the magnetic properties of a non-patterned thin film, such as its switching field, magnetization reversal mechanism and intrinsic magnetic anisotropy [16][17][18][19][20].…”

Magnetic NiFe thin films composing MoS2 nanostructures for spintronic application

“…Recent promising achievements in spintronics specially in magnetic thin films conjugated to two-dimensional (2D) materials has made this topic interesting for fundamental studies to explore their important role in the future spintronic-based memory and computing devices 1 – 5 . The core deriving fundamental phenomenon in such structures is the spin–orbit interaction (SOI) 6 , 7 .…”

Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size

“…Conventional methods to obtain CoO/Co with PMA use multilayer structures of AFM/FM/non-magnetic metal or metal oxide interfaces [ 27 , 28 , 29 ], but these methods may affect some magnetic parameters of CoO/Co, such as magnetization saturation ( M S ) and damping coefficient [ 28 , 30 ]. An alternative approach that has already proven its success with other materials, such as Co/Permalloy [ 31 , 32 ], consists of using antidot nanostructured templates, which allows tailoring the physical properties of any host-patterned material through the variation of its geometric parameters, such as the hole size and the neighboring interdistance [ 33 ]. In particular, it has been reported that, for FM/AFM antidot thin films, the coercivity and EB field can be engineered by controlling the thickness of the FM layer, the diameter of the pores, and the density of the pores [ 9 , 34 , 35 , 36 ].…”