Improved magnetoresistance through spacer thickness optimization in tilted pseudo spin valves based on L1 (111)-oriented FePtCu fixed layers

Abstract

Through optimization of the Cu spacer thickness, we demonstrate magnetoresistance ͑MR͒ up to 5% in FePtCu/CoFe/Cu/CoFe/NiFe pseudo spin valves based on L1 0 ͑111͒ FePtCu fixed layers with a tilted magnetization. We find an optimum spacer thickness of about 2.4 nm which correlates with a clear onset of strong interlayer exchange coupling below 2.4 nm and spin-independent current shunting in the spacer above 2.4 nm. We argue that yet higher MR should be possible through further reduction in the interlayer exchange coupling.

Continuously graded anisotropy in single (Fe53Pt47)100−xCux films

“…In addition, similar L1 0 FePtCu ͑111͒ films have been reported to have tilted anisotropies. 27,28 This fact, combined with the advantages of graded K u may result in a very versatile magnetic structure, which may not only be appealing for magnetic recording but also for STT applications. 29,30 We anticipate that the experimental procedure presented here can be further improved and extended to other, e.g., perpendicular and/or granular, material systems where a graded anisotropy is desired.…”

Depth-Dependent Magnetization Profiles of Hybrid Exchange Springs

“…For STOs, tilted materials offer a route to improve their microwave generation properties, both in terms of higher output power and low-to zero-field operation [17,[21][22][23]28,[30][31][32].Recently, tilted materials have also been shown to have potential for current-driven domain wall motion [33]. The influence of a tilted anisotropy is stronger than simply tilting the applied field [34] as a mere 5 degree misalignment between the free and the fixed layer in magnetic tunnel junctions (MTJs) can reduce the switching current by 36%, the switching time by 30%, and improve the switching current distribution [35].Materials with tilted anisotropies have been realized using collimated oblique sputtering [36], depositing multilayers on nanospheres [25], and exploiting crystallographic texture to control the magnetic easy axis in alloys such as (112)-textured D0 22 MnGa (with a tilt angle of 36°), and (111) or (101)-L1 0 FePt (with angles of 36° and 45°, respectively) [37][38][39]. Recently, an alternative and much more versatile approach was reported where exchange springs combining materials with out-of-plane (OOP) and IP anisotropies provide a wide and tunable range of tilt angles [40][41][42].…”

“…Materials with tilted anisotropies have been realized using collimated oblique sputtering [36], depositing multilayers on nanospheres [25], and exploiting crystallographic texture to control the magnetic easy axis in alloys such as (112)-textured D0 22 MnGa (with a tilt angle of 36°), and (111) or (101)-L1 0 FePt (with angles of 36° and 45°, respectively) [37][38][39]. Recently, an alternative and much more versatile approach was reported where exchange springs combining materials with out-of-plane (OOP) and IP anisotropies provide a wide and tunable range of tilt angles [40][41][42].…”

First-order reversal curve analysis of graded anisotropy FePtCu films

“…In order to improve surface roughness, ͑111͒-texture, and lower the chemical ordering temperature of the L1 0 phase, the FePtCu films are deposited on a bilayer of Ta ͑6 nm͒/Pt ͑3 nm͒ and capped with 5 nm of Ta to prevent oxidation. [23][24][25] The anisotropy gradient is then realized after thermal annealing at a suitable temperature and by exploiting the strong dependence of the A1 ͑low anisotropy͒ to L1 0 ͑high anisotropy͒ ordering temperature on the Cu content. 26 The Cu-rich regions transform from the as-deposited low anisotropy cubic A1 phase into the high anisotropy tetragonal L1 0 phase at a lower annealing temperature than the Cu-poor regions, thus establishing a continuous anisotropy gradient through the thickness of the film.…”