Markayendeyulu G

Ferromagnetic and ferroelectric characteristics of Gd and Nd-substituted nickel ferrite were investigated. The materials formed in the cubic inverse spinel phase with small amounts of GdFeO3 and NdFeO3 as the additional phases in the respective materials. Substitution of Gd and Nd for Fe caused decrease in the saturation magnetization and Curie temperature of the nickel ferrite. However, the saturation magnetostriction is seen not to change significantly by the substitution of Gd and Nd. The existence of the ferroelectricity was confirmed from the ferroelectric loops and magnetocapacitance of -2% and -3% were observed. The large frequency dependence of the (high) dielectric constant reveals a wide dispersion of relaxation times. The ferroelectric transition temperature values of NiO.Fe1.95Gd0.05O3 and NiO.Fe1.95Nd0.05O3 were found to be 498 and 544 K, respectively. © 2009 Elsevier B.V. All rights reserved.

The TbxHo0.75-xPr0.25(Fe0.9B0.1)2 (x=0, 0.1, 0.15, 0.2, 0.25, and 0.3) compounds are found to stabilize in a cubic Laves phase structure. The lattice parameter, magnetostriction (at 10 kOe), and Curie temperature are found to increase with increasing Tb content. The compound with x=0.15 exhibits a possible anisotropy compensation between the Tb and (Ho/Pr) sublattices. The easy magnetization direction rotates towards the 〈1 1 1〉 from the 〈1 0 0〉 direction, with increasing Tb content. The splitting of the (4 4 0) peak accompanied by the spontaneous magnetostriction-induced rhombohedral distortion is observed for compounds with x≥0.15 and the spontaneous magnetostriction (λ1 1 1) is found to increase with Tb content. © 2007 Elsevier B.V. All rights reserved.

Structural, electrical, and magnetoreactance (mr) characteristics of rare Earth-doped Ni ferrite (NiO.Fe2-xRxO3(x = 0. 0.075. R =- , and NiO.Fe1.95R0.05O3 ) were investigated. All the materials formed in the cubic inverse spinel phase with small amounts of RFeO3 as the additional phase. mr was measured in both longitudinal and transverse configuration. A mr of - 1477% was observed for pure nickel ferrite at 10 kHz while it is smaller for the rare Earth-doped compounds. With increasing frequency maximum mr value is found to decrease. The resistivity was found to decrease with increasing frequency for all the compounds and dispersion of relaxation times was observed. © 2009 IEEE.

Polycrystalline Sm0.9-xNdxPr0.1Fe1.93 (x = 0, 0.12, 0.2, 0.24, 0.32 and 0.36) intermetallic compounds were found to stabilize in MgCu2-type cubic Laves phase structure. The easy direction of magnetization (EMD) was seen to be along 〈1 1 1〉 direction, accompanied by a rhombohedral distortion in all the compounds, at room temperature. The spin reorientation temperatures were observed at 59 K (TSR1) and 190 K (TSR2) from the temperature dependent magnetization studies. The spin reorientation temperature (TSR2) was due to the change of EMD from 〈0 1 1〉 to 〈1 1 1〉. The order–disorder transition (Curie temperature: TC) was found to decrease with increasing Nd content. The anisotropy compensated Sm0.9Pr0.1Fe1.93 compound was found to exhibit the largest induced magnetostriction (λ‖-λ⊥) value of -1822×10-6, from the present studies, at an applied field of 10 kOe.

The structural and magnetic properties of bulk polycrystalline CoFe 2O4 and niobium substituted Co1.1Fe 1.85Nb0.05O4 prepared by solid state reaction method, are presented in this paper. The lattice parameter of Co 1.1Fe1.85Nb0.05O4 is seen to be more than that of CoFe2O4. Saturation magnetization, first order magnetocrystalline anisotropy constant calculated using law of approach to saturation and magnetostriction of Co1.1Fe1.85Nb 0.05O4 are seen to be less than those of CoFe 2O4. Longitudinal magnetostriction of Co 1.1Fe1.85Nb0.05O4 measured at room temperature is -123 × 10-6 at a field of 2.2 kOe, with enhanced strain derivative. Field induced trigonal distortion was observed at 2.2 kOe in Co1.1Fe1.85Nb0.05O4 from the analysis of powder XRD patterns. Co1.1Fe1.85Nb 0.05O4 exhibits ferroelectric and magnetoelectric properties. © 2014 Elsevier B.V. All rights reserved.

We report on the results pertinent to structural, magnetic, magnetostrictive studies of the Tb0.3Dy0.7-xNdxFe1.93 [x = 0, 0.05, 0.1, 0.15 and 0.2] compounds. From the evidenced magnetization and magnetostriction results, the crucial finding that we emphasize is that the realization of minimum anisotropy for the compound with the composition x = 0.1. From the X-ray diffraction on magnetically aligned samples, (4 4 0) peak splitting analysis and Mössbauer studies, we ascertain that the easy magnetization direction (EMD) for x = 0.2 compound it is towards 〈1 1 0〉. Above results also affirmed that indeed there exists transformation of the structural distortion from rhombohedral to orthorhombic from x = 0 to x = 0.2. The Laves phase compound Tb0.3Dy0.6Nd0.1Fe1.93 with a large magnetostriction (λ111 1270 × 10-6) and a low anisotropy may be a potential candidate for magnetostriction applications.