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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.

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]

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]

The concept of spin-filter spin-valve (SFSV) films is reviewed. The dependence of the free layer structure on the spin-filter effect was investigated by using model films and two types of free layers were compared, a single CoFe layer and a conventional NiFe/Co free layer. At the same magnetic thickness of the free layer, the SFSV films with a CoFe free layer showed a larger magnetoresistance (MR) ratio than those with a NiFe/Co free layer. This is partly attributed to the thinner CoFe free layer thickness, which is due to the fact that the CoFe free layer has higher B[sub s] than the NiFe/Co free layer. Moreover, SFSV films with a CoFe free layer still showed a larger MR ratio when the free layer thickness was the same. It suggests that other factors contribute to the high MR performance, such as the quality of the interface between a free layer and a high conductance layer. Film performance of MR 9% to 10%, ΔR[sub s] 1.5-2.0 Ω, H[sub c][sup ea]∼3 Oe, and λ[sub s]≤±0.5 ppm was obtained with a single CoFe free layer and synthetic antiferromagnetic pinned structure. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents an abstract of the study 'Influence of a Large Amount of Co Substitution on the Magnetic Properties of NdFeCoGaB Magnets,' by A. Tsutai, I. Sakai, M. Sahashi and K. Inomata.

We have investigated the microwave oscillations due to a spin transfer effect induced by direct current in ferromagnetic nanocontact magnetoresistive (NCMR) elements with a current-perpendicular-to-plane spin-valve structure consisting of an FeCo/FeCo–AlOx nano-oxide layer/FeCo multilayer for the reference/spacer/free layers, respectively. Characteristic microwave oscillations were observed in the NCMR elements at different magnetization states induced by the application of a spin-polarized current, which are considered to be related to the introduction of a ferromagnetic NC to spacer layer (large interlayer coupling) and the resonance concerning the stability of the magnetization states of the free and reference layers around the NCs. A marvelously narrow full width at half maximum (FWHM) of l0–20 MHz is observed under a high applied magnetic field where the reference layer magnetization is slightly off axis relative to the pinned direction. By contrast, a wider FWHM of 80–600 MHz is observed at the magnetization state where the magnetization of the free layer just aligned to the antiparallel configuration against the magnetization of the reference layer. These characteristic results are discussed in terms of a spin dynamics mechanism induced by spin transfer torque in the free and reference layers around NCs. [ABSTRACT FROM AUTHOR]

We have reported that body-centered-cubic (bcc) Fe[SUB50]Co[SUB50] with ultrathin Cu layers has large spin-dependent bulk scattering and enhances AΔR of spin valves. In order to clarify the role of Cu, two series of samples with (Fe[SUB50]Co[SUB50] (1 nm/Cu) × 5 were prepared by two different sputtering machines. Machine A has a high rate, and machine B has a comparatively low rate. Both of AΔR in series A and B are increased by inserting thin Cu of about 0.1 nm, but they have a significant difference in Cu thickness dependence. While series A keeps high AΔR through the Cu thickness, AΔR in series B decreases when Cu is thickened. In order to find the reason for the difference, we took the extended x-ray absorption structure (EXAFS) spectra. By comparing AΔR and EXAFS, it was found that the very thin Cu of about 0.1 nm in Fe[SUB50]Co[SUB50] takes a body-centered-cubic bcc structure, namely a solid solution state. Cu of 1 nm in spin valves with high AΔR takes a bcc and face-centered-cubic (fcc) evenly, and that with a low AΔR is a fcc structure. These results indicate that the existence of the solid solution Cu in Fe[SUB50]Co[SUB50] is attributable to the enhancement of AΔR 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. [ABSTRACT FROM AUTHOR]

To implement the specular nano-oxide-layer (NOL) spin valve (SV) heads for use in practical applications, it is key to simultaneously achieve a good specular effect of the NOL inserted in the synthetic ferrimagnet pinned layer (i.e., high magnetoresistance MR performance) and a strong pinning field through the NOL. By using CoFe+X as a substance to be subjected to oxidation, we obtained the NOL specular SV films simultaneously achieving a high MR ratio of 17%-18% and a high pinning field of 1100-1500 Oe. Narrow track (0.12 µm) heads were fabricated and they showed a high sensitivity of 10 mV/µm. Several reliability tests were done both at the sheet film level and the actual head level. The oxygen inside NOL was found to be stable up to 350 °C, and pinned layer magnetization canting after orthogonal field annealing was found to be almost the same as today's non-NOL SV films. An electrostatic discharge test and accelerated lifetime test were also performed and NOL specular heads were demonstrated to have almost the same robustness as today's non-NOL heads. [ABSTRACT FROM AUTHOR]

Three different techniques, natural oxidation, remote plasma oxidation and low energy ion beam oxidation, have been proved to be equally effective in forming nano-oxide layers (NOLs) in spin-valve films for specular enhancement of giant magnetoresistance (GMR) effect. GMR values over 12% have been routinely obtained in spin-valve films with NOL, corresponding to a 30% specular enhancement over those without NOL. The consistency and robustness of the oxidation processes has been demonstrated by a very large GMR value ∼19% in a dual spin-valve film with the NOLs formed in both pinned layers, the oscillatory dependence of the interlayer coupling field on Cu layer thickness in specular enhanced spin-valve films and the uniform and repeatable film performance over 5 in. substrates. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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.

Presents information on a study which investigates spin-valve structures with a magnetic material buffer layer, CoNbZr (100 Å)/NiFe (20 Å), on an oxidized silicon substrate. Measurement of the magnetoresistance ratio; Crystal structure; Experimental and calculated x-ray diffraction profile; X-ray diffraction method.

Presents a study that examined the magnetic properties and magnetostriction in grain-oriented compounds. Experimental method; Results and discussions; Conclusion.

In this study, we fabricated a Cr2O3 (0001) film without and with a Pt buffer layer and investigated its effect on perpendicular exchange coupling in a Cr2O3/Co3Pt interface. The results showed that the exchange bias field (μ0Hex) and blocking temperature (TB) of a Cr2O3 film without and with Pt were very different. The Cr2O3 film without Pt had a lower μ0Hex of 176 Oe and a lower TB of 75 K, whereas that with Pt had a higher μ0Hex of 436 Oe and a higher TB of 150 K. We discussed this difference in μ0Hex and TB values based on collinear/non-collinear coupling in a ferromagnetic and antiferromagnetic interface using Meiklejohn and Bean's exchange anisotropy model. [ABSTRACT FROM AUTHOR]

Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co3Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 °C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 Ω cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co3Pt surface oxidation was discussed. [ABSTRACT FROM AUTHOR]

The bulk and interface spin scattering asymmetric coefficients, βF and γF/N, respectively, as well as the interfacial specific resistance, AR*F/N, contribute to the total resistance change-area product, ΔRA, in current-perpendicular-to-plane (CPP) geometry. In this paper, we report the effect of the insertion of a 1 nm Fe layer into ferromagnetic (F)/non-ferromagnetic (N) interfaces on the spin dependent transport properties. Using the Valet-Fert theory based on the two-current model in which ΔRA is obtained as a function of thicknesses of the ferromagnetic layer (3, 4, and 5 nm), we experimentally deduced the values of βF, γF/N, and AR*F/N of exchange-biased spin valves (EBSVs) for an artificially ordered B2 state Fe50Co50 alloy as a magnetic layer and an Ag spacer layer. [ABSTRACT FROM AUTHOR]

Using current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) measurement, we have evaluated the bulk and interface spin scattering asymmetric coefficients, βF and γF/N and the specific interfacial resistance, AR*F/N, for exchange-biased spin-valves consisting of artificially ordered B2 structure Fe50Co50 and Ag spacer layer. Artificially epitaxial ordered Fe50Co50 superlattices have been successfully fabricated on MgO (001) substrate by alternate monatomic layer (AML) deposition at a substrate temperature of 75 °C. The structural properties of the full epitaxial trilayer, AML[Fe/Co]n/Ag/AML[Fe/Co]n, on the Ag electrode have been confirmed by in situ reflection high-energy electron diffraction and transmission electron diffraction microscopy. A considerably large resistance-area product change and MR ratio (ΔRA > 3 mΩμm2 and MR ratio ∼5%) were confirmed even at thin AML[Fe/Co]n layer at room temperature (RT) in our spin-valve elements. The estimated values of βF and γF/N were 0.80 and 0.84 ± 0.02, respectively, from the Valet-Fert theory analysis of ΔRA as a function of thickness of the ferromagnetic layer (3, 4, and 5 nm) on the basis of the two-current model. [ABSTRACT FROM AUTHOR]