Search

Research describing the magnetoresistance of spin-filter spin-valve films is presented. In particular free layer structures using ultrathin CoFe are compared with conventional free layers of the NiFE/Co type.

We investigated current-perpendicular-to-plane (CPP) magnetotransport parameters of FexCo100-x/ Ag interfaces: interface specific resistance (ARF/N), extended interface resistance (AR* F/N), and spin scattering asymmetry (γ). We also investigated the dependence of interfacial parameters on the giant magnetoresistance effect with CPP geometry. For measuring these parameters, we prepared magnetic multilayers and pseudo spin valves (PSVs), combining the ferromagnetic (F) alloys Fe, Co, Fe50Co50, and Fe30Co70 with the nonmagnetic (N) metal Ag. In all cases, the largest ARF/N value was found to be ~0.68 mΩμm² with an enhanced AR* F/N value of ~1.9 mΩμm² for a (001)-oriented Fe/Ag interface, which suggests that spin-up and spin-down electrons on the Fermi surface have very different transmission probabilities. Such an interface can act as a spin filter through which only one type of electrons can pass. [ABSTRACT FROM AUTHOR]

The head-level performance and reliability of nano-oxide-layer (NOL) specular spin valves (SVs) are examined. The pinned layer magnetization of the NOL heads was found to be stable like the non-NOL synthetic pinned layer in conventional heads. No significant difference in amplitude degradation was observed for the NOL and non-NOL heads after 200 h running.

It has been established that low energy ion beam oxidation, natural oxidation and remote plasma oxidation are equally effective in creating nano-oxide layers in spin-valve films for specular enhancement of giant magnetoresistance effect. It was possible to demonstrate the consistency and robustness of the oxidation processes.

Deposition and annealing behaviors of Al atoms on rough Cu (111) surface were investigated on the atomic scale by three-dimensional classical molecular dynamics simulation. The rough Cu surface was modeled by depositing 5 ML of Cu on Ta (011) substrate. Most Al atoms deposited on the rough Cu surface placed on the atomic steps, preserving the major features of the surface during Al deposition. This behavior was discussed in terms of the smaller barrier of the surface diffusion than Ehrlich–Schwoebel barrier of Al on Cu (111) surface. By annealing at 700 K, significant intermixing between Al and Cu rapidly occurs with decrease in the surface roughness. This behavior reveals that the exchange process of Al with substrate Cu dominates during the initial stage of high temperature annealing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The current-perpendicular-to-plane (CPP) giant-magnetoresistance (GMR) of spin valves with Fe50Co50 alloy was investigated. It has been reported that the Cu inserted in Fe50Co50 is effective for enhancing CPP-GMR. In this paper, we investigated the number of Cu lamination effect on CPP-GMR and clarified that higher CPP-GMR is obtained by decreasing the number of Cu layers. In order to ascertain the reason for this tendency, the crystalline structure and magnetization were examined. As a result, it was found that the d spacing of Fe50Co50 increases when the number of Cu layers is increased, although saturation magnetization does not change. [ABSTRACT FROM AUTHOR]

In this work, we present a suitable material for metal-based spin-valve in current-perpendicular-to-plane (CPP) geometry. The AΔR (A is the element size and ΔR is the change in resistance) was investigated for three kinds of free and pinned layers material, that is, Co[sub 90]Fe[sub 10], Fe[sub 50]Co[sub 50], and Fe[sub 50]Co[sub 50] with half-atomic Cu layers. When the free and pinned layers are 5 nm, AΔR is 1.0 mΩ/µm², 1.6 mΩ µm², and 2.9 mΩ µm², respectively. Moreover, the dual-type spin valve having Fe[sub 50]Co[sub 50] with half-atomic Cu layers achieved 5.2 mΩ µm². According to the free and pinned layers thickness dependence of AΔR, the spin-dependent resistance at the interfaces between ferromagnetic layers and spacer Cu is enhanced mainly by changing from Co[sub 90]Fe[sub 10] to Fe[sub 50]Co[sub 50], and the spin-dependent bulk resistance in free and pinned layers is enlarged by inserting half-atomic Cu layers. [ABSTRACT FROM AUTHOR]

A study of the magnetic properties and magnetostriction of grain-oriented (Tb(x)Dy(1-x))(Fe(1-y)Mn(y))1.95 compounds, prepared by Bridgman method, indicates an enhancement of lambda(100) and lowering of spin reorientation temperature with Mn substitution. Applying suitable stress induces good thermal stability and large magnetostriction in low applied fields when x is 0.5 and y is 0.1. This compound finds use in giant magnetostrictive actuators.

The microwave oscillations due to a spin transfer effect induced by direct current in ferromagnetic nanocontact magnetoresistive (NCMR) elements wit a current-perpendicular-to-plane spin-valve structure consisting of an FeCo/FeCo-Al[O.sub.x] nanooxide layer/FeCo multilayer for the reference/spacer/free layers are examined. A wider full width at half maximum (FWHM) of 80-600 MHz is observed at the magnetization state where the magnetization of the free layer is aligned to the antiparallel configuration against the magnetization of the reference layer.

The current-perpendicular-to-plane (CPP) giant-magnetoresistance (GMR) of spin valves with Fe50Co50 alloy is investigated. It is found that the d spacing of Fe50Cu50 increases when the number of Cu layers is increased, although saturation magnetization does not change.

The structural state of the inserted Cu is examined by the extended x-ray absorption structure (EXAFS) spectra so as to clarify the role of Cu in A DELTA R behavior. The results suggest that the existence of the solid solution Cu in Fe(sub 50)Co(sub 50) is due to the enhancement of A DELTA R and are consistent with the report that Cu impurity in Fe and Co enhances the difference between the subband resistivity of up and down spins.

Focuses on a study which investigated a complex new magnetic refrigerant, suitable for the ideal Ericsson cycle. Properties that act as a magnetic refrigerant; Factor that answer the need for a highly efficient small cryocooler; Processes that compose the refrigeration cycle of the Carnot cycle.

Presents a study which investigated the structural and magnetic properties of (R,Zr)(Fe,Co)[sub10](R=Nd,Sm) prepared by the rapid-quenching method. Influence of the presence of zirconium; Information on the saturation magnetization of crystals; Details of the magnetic hardening of the nitrogenated materials.

Nano-contact magnetoresistance (NCMR) spin-valves (SVs) using an AlO x nano-oxide-layer (NOL) have numerous nanocontacts in the thin AlO x oxide layer. The NCMR theoretically depends on the bulk scattering spin asymmetry ([Formula: see text]) of the ferromagnetic material in the nanocontacts. To determine the relationship between NCMR and [Formula: see text], we investigated the dependence of NCMR on the composition of the ferromagnetic material Co 1-x Fe x . The samples were annealed at 270 °C and 380 °C to enhance the MR ratio. For both annealing temperatures, the magnetorsistance ratio in the low-resistance area product region at less than 1 Ω μ m 2 was maximized for Co 0.5 Fe 0.5 . To evaluate [Formula: see text] exactly, we fabricated current-perpendicular-to-plane giant magnetoresistance SVs with Co 1-x Fe x /Cu/Co 1-x Fe x layers and used Valet and Fert's theory to solve the diffusion equation of the spin accumulation for a ferromagnetic layer/non-ferromagnetic layer of five layers with a finite diffusion length. The evaluated [Formula: see text] for Co 1-x Fe x was also maximized for Co 0.5 Fe 0.5 . Additionally, to determine the difference between the experimental MR ratio of NCMR SVs and the theoretical MR ratio, we fabricated Co 0.5 Fe 0.5 with oxygen impurities and estimated the decrease in [Formula: see text] with increasing oxygen impurity concentration. Our Co 0.5 Fe 0.5 nano-contacts fabricated using ion-assisted oxidation may contain oxygen impurities, and the oxygen impurities might cause a decrease in [Formula: see text] and the MR ratio.

In this study, we fabricated a Cr 2 O 3 (0001) film without and with a Pt buffer layer and investigated its effect on perpendicular exchange coupling in a Cr 2 O 3 /Co 3 Pt interface. The results showed that the exchange bias field (μ 0 H ex ) and blocking temperature (T B ) of a Cr 2 O 3 film without and with Pt were very different. The Cr 2 O 3 film without Pt had a lower μ 0 H ex of 176 Oe and a lower T B of 75 K, whereas that with Pt had a higher μ 0 H ex of 436 Oe and a higher T B of 150 K. We discussed this difference in μ 0 H ex and T B values based on collinear/non-collinear coupling in a ferromagnetic and antiferromagnetic interface using Meiklejohn and Bean's exchange anisotropy model.