Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Design and application of magnetostrictive materials

The innovative core-ring structured NiCo2O4 nanoplatelets were found to be novel and promising photocatalysts. The physical and photophysical properties of the photocatalyst were characterized by SEM, TEM, XPS, UV−vis absorption, and photoluminescence, respectively. The core-ring NiCo2O4 nanoplatelets were composed of much smaller nanocrystallines, with an average size of 80−150 nm, compared to the ordinary NiCo2O4 prepared through a conventional hydroxide decomposition method. Moreover, the optical band gap energies of the core-ring NiCo2O4 nanoplatelets were estimated to be 2.06 and 3.63 eV from the UV−vis absorption spectra. The core-ring structured NiCo2O4 photocatalyst exhibited a much higher photocatalytic activity for the degradation of methylene blue than the ordinary NiCo2O4 and TiO2 under visible light irradiation (>420 nm). This enhanced photocatalytic activity of the core-ring NiCo2O4 nanoplatelets was attributed to their higher optical absorption ability, smaller particle size, and more activ...

Photophysical and Photocatalytic Properties of Core-Ring Structured NiCo2O4 Nanoplatelets

The authors show that the magnetization of a 2-phase magnetostrictive/piezoelectric multiferroic single-domain shape-anisotropic nanomagnet can be switched with very small voltages that generate strain in the magnetostrictive layer. This can be the basis of ultralow power computing and signal processing. With appropriate material choice, the energy dissipated per switching event can be reduced to ∼45 kT at room temperature for a switching delay of ∼100 ns and ∼70 kT for a switching delay of ∼10 ns, if the energy barrier separating the two stable magnetization directions is ∼32 kT. Such devices can be powered by harvesting energy exclusively from the environment without the need for a battery.

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Hybrid spintronics and straintronics: A magnetic technology for ultra low energy computing and signal processing

Publisher Summary This chapter discusses the magnetocaloric effect (MCE) in the vicinity of phase transitions Magnetothermal properties of materials were demonstrated because of their significance for the development of fundamental and applied magnetism These phenomena have a strong influence on the character of the behavior of such fundamental physical quantities as the entropy, specific heat, and thermal conductivity, and could lead to a number of extra anomalies in the dependencies of the material properties on temperature, magnetic field, and some other external parameters The MCE is the change of the initial temperature of a magnetic material as an external magnetic field is applied under conditions of constant total entropy of the material It describes the processes of entropy variation of the magnetic subsystem The chapter discusses the character of the MCE behavior in different magnetic materials and reviews the studies of this effect The materials with magnetic moments of either band or localized origin, and materials where the magnetic ordering can have collinear, and more complicated character, such as helical are reviewed in the chapter The MCE is utilized in magnetic refrigeration machines

Chapter 4 Magnetocaloric effect in the vicinity of phase transitions

Actuation and transduction by giant magnetostrictive alloys

Magnetic and magnetoelastic measurements under various conditions of compressive stress and applied field have been carried out on samples with the composition Tb0.3Dy0.7(Fe1−xAlx)1.95, 0≤x≤0.1, prepared by a float‐zone growth technique. Their magnetoelastic performances compare favorably with the highly magnetostrictive ‘‘Terfenol‐D’’ compounds by having large magnetostrictive strains (λ∼1200 ppm at ∼120 kA/m), good magnetomechanical coupling (k33≊62%) and a large strain coefficient (d33≊80 nm/A). The substitution of aluminum for iron produces a material with potential benefits for use in actuators: higher electrical resistivity and improved ductility, which reduce eddy current effects and increase the mechanical strength.

Magnetoelastic effects in rare‐earth iron‐aluminum compounds

The properties and applications of magnetostrictive rare-earth compounds

The DC field and pressure dependencies of the magnetic induction (B) and magnetostrictive strain ( lambda ) have been measured at room temperature in Terfenol-D (Tb/sub 0.3/Dy/sub 0.7/Fe/sub 1.95/) and in the compound Tb/sub 0.3/Dy/sub 0.7/(Fe/sub 0.9/ Al/sub 0.1/)/sub 1.95/. From these data the static differential permeability ( mu ) and strain coefficient (d/sub 33/=d lambda /dH) have been obtained. A comparison of their magnetostrictive responses indicates that the magnetocrystalline anisotropy is reduced by the addition of Al to Terfenol-D. A slight lowering of d/sub 33/ with Al content is attributed to a reduction in magnetoelastic coupling, also seen in a lower magnetomechanical coupling coefficient. The work done by either compound against the applied pressure for different isostatic fields has been calculated. From these curves the residual stress levels, T/sub 0/, are substantially lower than those reported previously in Tb/sub 0.27/Dy/sub 0.73/Fe/sub 2/, indicating that in the present compounds T/sub 0/ is due mainly to inhomogeneities and defects, rather than anisotropy. >

Magnetomechanical behaviour of rare earth iron-aluminium compounds

The magnetomechanical properties of Terfenol have been determined by two independent experimental techniques. Measurements on several samples of the same nominal compositions made by free-float zoning reveal variations in quality. With a novel technique for scanning along the length of a Terfenol rod, structural defects can be detected which may explain these variations. A difference between magnetostrictive surface and bulk strains has been observed, and the frequency response of the former is substantially different from theoretical predictions, casting doubt on techniques for the characterization of Terfenol which involve the use of dynamic (AC) fields to measure the magnetostrictive strain coefficient. A description of the control strategies used to implement the actuation of Terfenol-based transducers is given. >

R.D. Greenough

Papers

Actuation and transduction by giant magnetostrictive alloys

Magnetoelastic effects in rare‐earth iron‐aluminum compounds

The properties and applications of magnetostrictive rare-earth compounds

Magnetomechanical behaviour of rare earth iron-aluminium compounds

Actuation with Terfenol-D