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Because of its highest magnetostriction at room temperature, TbFe2 is one of the most promising materials for magnetostrictive applications. However, oxidation-induced deterioration in its magnetic properties limits its usage at higher temperature (T) and/or longer time (t). In this regard, a systematic study is performed here to understand the effect of oxide-film overgrowth (by varying T and t) on the microstructure and magnetic properties of TbFe2. The characteristic parameters of magnetic properties, such as coercivity (Hc) and remanent magnetization (Mr), are found to decrease with increasing T and/or t. Moreover, a strong correlation between the oxidation-induced microstructure and magnetic properties is observed. Understanding developed in this study will help in choosing optimum working conditions (i.e., T and/or t) for TbFe2 to avoid significant deterioration in the magnetic properties. [ABSTRACT FROM AUTHOR]

Abstract: In this work we have studied the magnetic anisotropy of as-grown TbFeGa ternary alloys with a Ga doping between 10 and 16% and a Tb content between 9 and 12%. The samples were deposited by cosputtering at room temperature in the oblique incidence from two targets with a TbFe2 and Fe3Ga nominal composition. Samples with different compositions were achieved keeping constant the DC growth power at 100W in the TbFe2 and modifying the pulsed power between 60 and 120W in the Fe3Ga target, respectively. The X-ray diffraction patterns indicate the presence of crystalline TbFe2-based phases. It has been obtained perpendicular magnetic anisotropy in all the samples except when the pulsed power increases up to 120W that corresponds to a 16% of Ga. The existence of perpendicular magnetic anisotropy seems to be related to the presence of TbFe2-based phases with a composition close to the TbFe2. [Copyright &y& Elsevier]

Abstract: Fine magnetic powder of a terbium–iron intermetallic compound, TbFe2, was prepared by electrochemical reduction of thermally compounded powders of Tb4O7 and Fe2O3 (atomic Tb/Fe ratio, 1:2) in molten CaCl2. The electro-reduction potential of mixed Tb4O7 and Fe2O3 powders was more positive than that of Ca2+ in molten CaCl2 as revealed by cyclic voltammetry using a novel metallic cavity electrode. Porous pellets of mixed Tb4O7 and Fe2O3 powders were prepared by sintering in air, and were reduced to various Tb–Fe intermetallic compounds by constant voltage electrolysis at typically 2.6–3.2V and 900°C for 10–12h. The electrolytic product could be cleaned effectively in dimethylsulfoxide under magnetic stirring, leading to a pure magnetic powder with a low oxygen content (<1300ppm) and the desired TbFe2 stoichiometry as confirmed by XRD and ICP-AAS. It was also found that raising the sintering temperature (1200°C, 2h) encouraged compound formation between Tb4O7 and Fe2O3 powders and led to better stoichiometry control in the electrolytic product. Energy consumption of the electrolysis could be lower than 14kWh/kg TbFe2, and the Tb recovery yield reached beyond 97%. [Copyright &y& Elsevier]

Abstract: Epitaxial, (211)-oriented thin films of (R: rare earth; here: Dy, Tb) were deposited by molecular beam epitaxy on faceted and non-faceted - () (m-plane) substrates utilizing a 15Å thin Fe seed layer and a 500Å Nb buffer layer. Detailed X-ray diffraction analyses revealed a twin-free epitaxial (211)-oriented growth of buffer layer and film. The magnetostrictive layer , as well as the template layers Nb and Mo exhibited the same crystallographic in-plane orientation with regard to the substrate. The same epitaxial relationship was found for films prepared on faceted and on non-faceted substrates. This implies a coherent crystal overgrowth of the epilayers over the facet ridges. Magnetization measurements of the films revealed coercive fields of 0.4T for and 0.13T for . The magnetoelastic coefficients at 1.1T amounted to and for the and thin films, respectively. [Copyright &y& Elsevier]

We performed unidirectional solidification experiments on TbFe2 alloy in a static magnetic field in microgravity of 10-4g for 10sec obtained by a 490m free fall of the Japan microgravity center (JAMIC). When the magnetic field strength was increased from zero to 4.5 × 1-2T during unidirectional solidification in microgravity, a [111] crystallographic alignment dominated, and the maximum magnetostriction constant increased from 1,000 ppm to 4,000 ppm. For unidirectional solidification in normal gravity, the maximum magnetostriction constant remained at 2,000 ppm with increasing magnetic field. The columnar structure grows and orients along the magnetic field. TbFe2 crystals grow in microgravity predominantly in the same direction as the magnetic field. [ABSTRACT FROM AUTHOR]

Giant magnetostrictive TbFe2 thin films were prepared by the ion plating process. The films were treated by Ar plasma irradiation and heat-treatment. The plasma irradiation was carried out at low plasma energy by a high heat flux sheet plasma system. Both treatments lead to the increase in the maximum magnetostriction and the magnetostrictive susceptibility at low magnetic field. The plasma irradiation effects seem to be due to the heat generation during irradiation. The magnetostrictive characteristics are affected by the increase in in-plane anisotropy magnetization by treatments. [Copyright &y& Elsevier]

In this study, the effects of geometrical arrangement of substrate on the magnetostriction of the giant magnetostrictive materials film using an ion plating process were discussed. With increasing substrate angle, coercive force remained almost constant value and the in-plane magnetization at 15 kOe was strongly increased. This indicates that the easy direction of magnetization was changed from perpendicular to in-plane by obliquely deposition. The magnetic and magnetostrictive characteristics of the obliquely deposited films were affected by an oblique anisotropy. The oblique anisotropy may be induced by the shape anisotropy connected with columnar grain morphology. [Copyright &y& Elsevier]