There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

http://science.sciencemag.org/content/sci/294/5546/1488.full.pdf

Spintronics: a spin-based electronics vision for the future.

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

/pdf/spintronics-fundamentals-and-applications-2dx38n6phu.pdf

Spintronics: Fundamentals and applications

A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements. A ferromagnetic crystal exhibits a stable and switchable magnetization that arises through the quantum mechanical phenomenon of exchange. There are very few 'multiferroic' materials that exhibit both of these properties, but the 'magnetoelectric' coupling of magnetic and electrical properties is a more general and widespread phenomenon. Although work in this area can be traced back to pioneering research in the 1950s and 1960s, there has been a recent resurgence of interest driven by long-term technological aspirations.

/pdf/multiferroic-and-magnetoelectric-materials-2fpof7uzog.pdf

Multiferroic and magnetoelectric materials

A negative isotropic magnetoresistance effect more than three orders of magnitude larger than the typical giant magnetoresistance of some superlattice films has been observed in thin oxide films of perovskite-like La0.67Ca0.33MnOx. Epitaxial films that are grown on LaAIO3 substrates by laser ablation and suitably heat treated exhibit magnetoresistance values as high as 127,000 percent near 77 kelvin and ∼1300 percent near room temperature. Such a phenomenon could be useful for various magnetic and electric device applications if the observed effects of material processing are optimized. Possible mechanisms for the observed effect are discussed.

http://science.sciencemag.org/content/sci/264/5157/413.full.pdf

Thousandfold Change in Resistivity in Magnetoresistive La-Ca-Mn-O Films

Spin Transport in Carbon Nanotubes and Graphene: Experiments and Theory

The authors present a study of the non-linear magnetisation in the vicinity of the freezing temperature Tf of the insulating spin glass Fe0.3Mg0.7Cl2. The magnetisation of the sample was measured in the range 1 or=1.70K and for a slow cooling rate of 0.5 mK s-1 the equilibrium magnetisation is obtained. In these experimental conditions, non-linear effects are studied and a rapid increase of the non-linear part mod M- chi 0H mod of the magnetisation is observed when decreasing the temperature down to 1.7K. The present the temperature dependence of the two first non-linear coefficients a3 and a5 (b3 and b5) in the expansion of (M- chi 0H) in function of odd powers of H( chi 0H). Coefficients b3 and b5 vary by one and two orders of magnitude in the temperature range 1.70-2.50K. Comparison with both simple superparamagnetic and typical spin glass systems is made.

Non-linear magnetisation effects in the spin glass Fe0.3Mg0.7Cl2

Early experiments to define oscillations in the CIP magnetoresistance (CIP-MR) of Ag/Co analogous to those for tcu < 5nm in Cu/Co were unsuccessful. The MR in this region was very small. Later experiments by Araki using thin (0.6nm ) Co layers produced much larger MRs and lead us to look at the MRs of similar samples more closely. We conclude that the large MR of such samples is associated with the discontinuous nature of the Co layers. The object of the present paper is to combine the high MR associated with the thin Co layers with the field dependence governed by the magnetization reversal in thick, and magnetically soft permalloy (Py) layers. We have measured the CIP-MR of sputtered samples of the [Co(O.4 nm)/Ag(tAg)/Py(tpy)/Ag(tAg)]×15 system with tAg ranging from 1.05 to 4nm and with tpy = 2 or 4nm. We obtain MRs at 4.2K as large as 35% in less than 100e with slopes as high as 5%/Oe. With CPP measurements slopes as high as 10%/Oe have been obtained. Squid magnetometer measurements indicate that, as the temperature increases, there is a crossover to superparamagnetic behaviour and a resulting gross deterioration of the MR slopes at room temperature. Efforts to increase the room temperature sensitivity are described. Detailed measurements of the CPP-MR of the [Co(0.4nm)/Ag(4nm)/Py(tpy)/Ag(4nm)]x20 series of multilayers are consistent with a two spin band model modified to take account of the granular nature of the Co.

Giant Magnetoresistance in Hybrid Magnetic Nanostructures Including Both Layers and Clusters

We have studied the temperature and magnetic field dependence of the conductivity of ${\mathrm{Au}}_{\mathit{x}}$${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$/Si (x=1, 0.54, 0.46, and 0.41) and Cu/Si multilayers. The individual layer thicknesses were from 9 to 20 \AA{} and from 21 to 86 \AA{} for metal and silicon layers, respectively. When silicon layers are thinner than about 40 \AA{}, the onset of a coupling between the metallic layers through the silicon layers is observed. For thicker silicon layers, the two-dimensional electron localization and interaction models correctly account for the data. The analysis of magnetoresistance and conductivity data yields consistent results and thus allows us to derive the temperature and composition dependence of the relevant scattering rates.

Temperature and magnetic field dependence of the two-dimensional conductivity in Au x Si 1-x /Si and Cu/Si multilayers

Magnetic skyrmions are arguably the smallest stable magnetic configuration in films, and therefore could be the ultimate magnetic storage bit [1,2] They have also triggered a wide interest due to the new fundamental phenomena related to their topology Numerical simulations have shown that the interfacial Dzyaloshinskii-Moriya interaction (DMI) can stabilize such skyrmions in nanoscale disks or tracks for a rather large range of DMI amplitudes for which the skyrmion can either be the ground state or metastable relative to the uniform state [4,5,6] Here, we demonstrate experimentally the presence of skyrmions in metallic multilayers structures engineered to exhibit a strong DMI interaction

Albert Fert

Papers

Spin Transport in Carbon Nanotubes and Graphene: Experiments and Theory

Non-linear magnetisation effects in the spin glass Fe0.3Mg0.7Cl2

Giant Magnetoresistance in Hybrid Magnetic Nanostructures Including Both Layers and Clusters

Temperature and magnetic field dependence of the two-dimensional conductivity in Au x Si 1-x /Si and Cu/Si multilayers

Skyrmions at room temperature in magnetic multilayers