Abstract
In this letter, we discuss the shift observed in spintronics from the current-perpendicular-to-plane geometry towards lateral geometries, illustrating the new opportunities offered by this configuration. Using CoFe-based all-metallic LSVs, we show that giant magnetoresistance variations of more than 10% can be obtained, competitive with the current-perpendicular-to-plane giant magnetoresistance. We then focus on the interest of being able to tailor freely the geometries. On the one hand, by tailoring the non-magnetic parts, we show that it is possible to enhance the spin signal of giant magnetoresistance structures. On the other hand, we show that tailoring the geometry of lateral structures allows creating a multilevel memory with high spin signals, by controlling the coercivity and shape anisotropy of the magnetic parts. Furthermore, we study a new device in which the magnetization direction of a nanodisk can be detected. We thus show that the ability to control the magnetic properties can be used to take advantage of all the spin degrees of freedom, which are usually occulted in current-perpendicular-to-plane devices. This flexibility of lateral structures relatively to current-perpendicular-to-plane structures is thus found to offer a new playground for the development of spintronic applications.
Highlights
The control of multilayers growth has been a key factor for the development of spintronics
The effects usually observed in current-perpendicular to the plane (CPP) can be observed in lateral devices[2, 3] which are nowadays widely used in spintronics
Most functional spintronic applications remain based on a CPP geometry[5], and on the use of magnetic tunnel junctions[6]
Summary
This implies that a decrease by a factor two of the wire width should lead to an eight times increase of the spin signal, and a four times increase of the GMR ratio. The maximum is not obtained for the smallest spacer, but rather surprisingly appears at a large width of 250 nm (for a signal of 0.163 Ω), which corresponds to a width-over-length-ratio exceeding one This behaviour can be reproduced by simulations (cf Fig. 2b) performed using finite element method, and based on a two spin-current drift-diffusion model[22]. The simplest geometry, corresponding roughly to a CPP GMR Pillar, would be that of a device with wires of CoFe and Al of equal widths This geometry, which one could naïvely supposed to be the one giving the best spin signal, is quite different from the non-intuitive, optimized geometry, with a spacer width of 250 nm instead of 50 nm.
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