The magnetoresistance origin of FeCo nanocontacts with current-perpendicular-to-plane spin-valve structure (invited)

Abstract

We have developed the FeCo nanocontact magnetoresistance (NCMR) with spin-valve structure [H. N. Fuke et al., IEEE Trans. Magn. 43, 2848 (2007)] which exhibits up to a MR ratio of 11%–12% at a resistance area (RA) of 0.3–0.55 Ω μm2. The nanocontact configurations were estimated at about 2 nm in in-plane diameter, 1.2 nm in thickness, and 0.55% in density for a RA∼0.5 Ω μm2 film based on in-plane current distribution by conductive atomic-force microscopy cross sectional transmission electron microscope images of the NCMR. The origin of the NCMR was discussed by comparing magnetic field dependence of resistance, with micromagnetics simulation based on the diffusive MR theory. It is found that our NCMR cannot be explained by diffusive domain wall theory or bulk scattering in free and pinned layers. It is likely that a theory on the basis of a ballistic MR consideration is needed to interpret our MR origin.

Thermal stability of the geometrically constrained magnetic wall and its effect on a domain-wall spin valve

“…In this work, we use the values of A ¼ 26 pJ/m and J s ¼ 2.2 T. These values correspond to material parameters for the conventional magnetic materials of nano-constrictions, i.e., iron and cobalt. 3,4 The value of the lattice constant a is set at 0.4 nm. By substituting these values into Eq.…”

“…2 One of the magnetoresistance (MR) elements in small read heads is the domain-wall spin valve. [3][4][5][6][7][8][9] The domain-wall spin valve consists of a magnetic metal nano-constriction between magnetic metal free and fixed layers as shown in Fig. 1(a).…”

Low-nonlinearity spin-torque oscillations driven by ferromagnetic nanocontacts

“…On the other hand, the Ion-Assisted Oxidation (IAO) of ultra-thin aluminum reproducibly was used to fabricate a 1-nm-thin alumina Nano-Oxide Layer (NOL) with direct 2-nm Nano-Contacts (NCs) between FM layers. [16][17][18][19][20] In NOL-based STOs, moderate power and narrow linewidths were reported, [21][22][23][24] with oscillation behavior similar to low-TMR-STO. 25 There is evidence for the presence of FM metallic NCs by magnetoresistance and transport properties, 17 transmission-electron micrographs, 18,20,26 and conductive atomic force microscopy.…”

“…[16][17][18][19][20] In NOL-based STOs, moderate power and narrow linewidths were reported, [21][22][23][24] with oscillation behavior similar to low-TMR-STO. 25 There is evidence for the presence of FM metallic NCs by magnetoresistance and transport properties, 17 transmission-electron micrographs, 18,20,26 and conductive atomic force microscopy. 18,19,26 However, the measured Nano-Contacts Magnetoresistance (NCMR) ratios are far below expectation compared with scattering from confined Domain-Walls (DW), [27][28][29] mostly due to the presence of oxygen and non-magnetic impurities.…”

Penetration of a Magnetic Wall into Thin Ferromagnetic Electrodes of a Nano-Contact Spin Valve

“…Magnetic walls have attracted much attention as a basic element of nano-spintronics devices such as a racetrack memory 1 , spin-wave logic gates 2 , a read-head for ultra-high-density magnetic recording [3][4][5] , and a spintorque oscillator (STO) [6][7][8][9][10][11] . The nano-contact spin valve with a geometrically confined magnetic wall shown in Fig.…”