In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Magnetocaloric effect: From materials research to refrigeration devices

Phase transitions and structural and magnetic properties of rapidly solidified Ni50Mn38Sn12 alloy ribbons have been studied. Ribbon samples crystallize as a single-phase, ten-layered modulated (10M) monoclinic martensite with a columnar-grain microstructure and a magnetic transition temperature of 308 K. By decreasing the temperature, martensite undergoes an intermartensitic phase transition around 195 K. Above room temperature, the high temperature martensite transforms into austenite. Below 100 K, magnetization hysteresis loops shift along the negative H-axis direction, confirming the occurrence of an exchange bias effect. On heating, the thermal dependence of the coercive field HC shows a continuous increase, reaching a maximum value of 1017 Oe around 50 K. Above this temperature, HC declines to zero around 195 K. But above this temperature, it increases again up to 20 Oe falling to zero close to 308 K. The coercivity values measured in both temperature intervals suggest a significant difference in the...

Structural and magnetic characterization of the intermartensitic phase transition in NiMnSn Heusler alloy ribbons

Review of physical vapor deposited (PVD) spectrally selective coatings for mid- and high-temperature solar thermal applications

United States. Advanced Research Projects Agency-Energy (Awards DE-AR0000471 and DE-AR0000181)

Concentrating Solar Power.

A tandem absorber of TiAlN∕TiAlON∕Si3N4 is prepared using a magnetron sputtering process The graded composition of the individual component layers of the tandem absorber produces a film with a refractive index increasing from the surface to the substrate, which exhibits a high absorptance (095) and a low emittance (007) The tandem absorber is stable in air up to 600°C for 2h, indicating its importance for high temperature solar selective applications The thermal stability of the tandem absorber is attributed to high oxidation resistance and microstructural stability of the component materials at higher temperatures

TiAlN∕TiAlON∕Si3N4 tandem absorber for high temperature solar selective applications

Deposition and characterization of TiAlN/TiAlON/Si3N4 tandem absorbers prepared using reactive direct current magnetron sputtering

We report the effect of Ni/Mn variation on the exchange bias properties in the bulk Mn-rich Ni50−xMn37+xSn13 (0 ≤ x ≤ 4) Heusler alloys. The excess Mn content was found to increase the exchange bias field while it decreases the exchange bias blocking temperature (TEB) from 149 to 9 K. A maximum shift in the hysteresis loop of 377 Oe is observed for the Ni46Mn41Sn13 alloy. As compared to Mn/Sn variation, Ni/Mn variation strongly influences the exchange bias properties in Ni-Mn-Sn alloys. We observed that if the Mn content is above 37 at. % in Ni-Mn-Sn alloys, the TEB value would show a decreasing trend either by varying the Ni or Sn content.

Effect of Ni/Mn concentration on exchange bias properties in bulk Ni50−xMn37+xSn13 Heusler alloys

The crystallographic structure and magnetic anisotropy have been investigated in Co/Pt multilayers deposited by direct current magnetron sputtering on two different buffer layers, Ta and Pt Detail theoretical and experimental investigations reveal the presence of three effects: magneto-elastic, interface and shape anisotropies, and their competition results in three distinct regions based on the Co layer thickness (tCo) In the region I, with tCo 12 A, the magneto-elastic effect emerges as an interface phenomena and the shape anisotropy becomes dominant

D.V. Sridhara Rao

Papers

TiAlN∕TiAlON∕Si3N4 tandem absorber for high temperature solar selective applications

Deposition and characterization of TiAlN/TiAlON/Si3N4 tandem absorbers prepared using reactive direct current magnetron sputtering

Effect of Ni/Mn concentration on exchange bias properties in bulk Ni50−xMn37+xSn13 Heusler alloys

Effect of coherent to incoherent structural transition on magnetic anisotropy in Co/Pt multilayers

Influence of substrate temperature on structure, microstructure and magnetic properties of sputtered Fe-Ga thin films