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.

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Spintronics: Fundamentals and applications

We review the basic physics of surface-plasmon excitations occurring at metal/dielectric interfaces with special emphasis on the possibility of using such excitations for the localization of electromagnetic energy in one, two, and three dimensions, in a context of applications in sensing and waveguiding for functional photonic devices. Localized plasmon resonances occurring in metallic nanoparticles are discussed both for single particles and particle ensembles, focusing on the generation of confined light fields enabling enhancement of Raman-scattering and nonlinear processes. We then survey the basic properties of interface plasmons propagating along flat boundaries of thin metallic films, with applications for waveguiding along patterned films, stripes, and nanowires. Interactions between plasmonic structures and optically active media are also discussed.

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Plasmonics: Localization and guiding of electromagnetic energy in metal/dielectric structures

Transparent conductors as solar energy materials: A panoramic review

Some of the most relevant finite-size and surface effects in the magnetic and transport properties of magnetic fine particles and granular solids are reviewed. The stability of the particle magnetization, superparamagnetic regime and the magnetic relaxation are discussed. New phenomena appearing due to interparticle interactions, such as the collective state and non-equilibrium dynamics, are presented. Surface anisotropy and disorder, spin-wave excitations, as well as the enhancements of the coercive field and particle magnetization are also reviewed. The competition of surface and finite-size effects to settle the magnetic behaviour is addressed. Finally, two of the most relevant phenomena in the transport properties of granular solids are summarized namely, giant magnetoresistance in granular heterogeneous alloys and Coulomb gap in insulating granular solids.

https://iopscience.iop.org/article/10.1088/0022-3727/35/6/201/pdf

Finite-size effects in fine particles: magnetic and transport properties

Magnetic sensors can be classified according to whether they measure the total magnetic field or the vector components of the magnetic field. The techniques used to produce both types of magnetic sensors encompass many aspects of physics and electronics. Here, we describe and compare most of the common technologies used for magnetic field sensing. These include search coil, fluxgate, optically pumped, nuclear precession, SQUID, Hall-effect, anisotropic magnetoresistance, giant magnetoresistance, magnetic tunnel junctions, giant magnetoimpedance, magnetostrictive/piezoelectric composites, magnetodiode, magnetotransistor, fiber optic, magnetooptic, and microelectromechanical systems-based magnetic sensors. The usage of these sensors in relation to working with or around Earth's magnetic field is also presented

Magnetic sensors and their applications

We present experimental results of unprecedented large magnetoresistance obtained in stable electrodeposited Ni–Ni nanocontacts 10–30 nm in diameter. The contacts exhibit magnetoresistance of up to 700% at room temperature and low applied fields and, therefore, act as very effective spin filters. These large values of the magnetoresistance are attributed to spin ballistic transport through a magnetic “dead layer” at the contact of width of about 1 nm or smaller. Nanometer sized, high sensitive magnetoresistive sensors could become key elements for magnetic storage in the terabit/in.2 range and in high density magnetic random access memories.

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Ballistic magnetoresistance in a magnetic nanometer sized contact: An effective gate for spintronics

We show that, at multiple scattering, the scattered field amplitude at a plane close to the surface of a perfectly reflecting grating, and thus the image of the grating, does not at all resemble the grating profile. We demonstrate the performance of an inverse-scattering procedure that applies within the range of validity of the Rayleigh hypothesis and that permits the attainment of superresolution in the reconstructed surface profile. This is the first solution, to our knowledge, for cases in which the near-field optics methods established so far do not work.

Near-field optics inverse-scattering reconstruction of reflective surfaces

We show that ballistic magnetoresistance exhibits universal scaling in atomic or nanometer scale contacts. Plotting the data as conductance, we find that, if the maximum magnetoconductance is normalized to unity and the conductance is scaled with the conductivity of the bulk material, the data fall in a narrow region, independent of the nanocontact materials, for our four data sets and four from the literature. The results agree with a theory that takes into account spin-scattering within a magnetic-domain wall.

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Universal Scaling of Ballistic Magnetoresistance in Magnetic Nanocontacts

This letter shows that the ballistic magnetoresistance of Fe at room temperature and low magnetic fields is ten times smaller than for Ni and Co. The results are well explained by theory that provides a global understanding for 3d transition metals because, for Fe, the ratio of majority to minority spins at Fermi level is much smaller than for Ni and Co. The data indicate that conduction is carried out by majority d electrons in the case of Fe, in contrast to what happens for Ni and Co.

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Ballistic magnetoresistance in transition-metal nanocontacts: The case of iron

A freshly cleaved surface of ferroelectric triglycine sulfate (TGS) has been studied by scanning friction force microscopy. Well‐defined areas, exhibiting a strong contrast difference, have been found just after cleavage in the ferroelectric phase. These regions correspond to different ferroelectric domains. ‘‘Interactions’’ between small regions and large negative domains are also observed leading us to conclude that these small features could be interpreted as nuclei of negative domains inside the positive one, evidence of the domain structure branching at the submicron scale.

Friction force microscopy study of a cleaved ferroelectric surface: Time and temperature dependence of the contrast, evidence of domain structure branching

N. Garcia

Papers

Ballistic magnetoresistance in a magnetic nanometer sized contact: An effective gate for spintronics

Near-field optics inverse-scattering reconstruction of reflective surfaces

Universal Scaling of Ballistic Magnetoresistance in Magnetic Nanocontacts

Ballistic magnetoresistance in transition-metal nanocontacts: The case of iron

Friction force microscopy study of a cleaved ferroelectric surface: Time and temperature dependence of the contrast, evidence of domain structure branching