B. Venkateswarlu

Bio: B. Venkateswarlu is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Materials science & Rietveld refinement. The author has an hindex of 3, co-authored 5 publications receiving 37 citations.

Complex Magnetic Behavior of the Heusler Alloy—Cu 2 Mn 0.75 Fe 0.25 Al

Abstract: We investigated the structural and magnetic properties of Cu 2 Mn 1-x Fe x Al (x = 0.25, 0.5, 0.75) alloys. Among the three compositions, only x = 0.25 composition crystallizes in single phase with L2 1 structure but its magnetic response indicates a complex magnetic structure. The magnetic isotherms were fitted to modified Langevin equation which indicates the presence of clusters with large magnetic moment. The ac susceptibility studies showed the presence of a superparamagnetic phase in the system over and above ferromagnetic order. To determine the nature of the interactions among the clusters, the variation of freezing temperature (T f ) with applied ac frequency was analyzed using different models (Neel-Arrhenius, Vogel-Fulcher, and critical slowing down model).

Influence of Surfactant Variation on Effective Anisotropy and Magnetic Properties of Mechanically Milled Magnetite Nanoparticles and Their Biocompatibility

Abstract: Magnetite nanoparticles were prepared with starch as surfactant by ball milling for 30 h a toluene medium. The nanoparticles were synthesized with different amounts of surfactant addition (8-12 wt%) and the variation in their effective anisotropy and magnetic properties with surfactant content is investigated. The samples were characterized by X-ray diffraction, FT-IR, and scanning electron microscopy. Magnetic measurements were carried out using a vibrating sample magnetometer. The cytotoxicity of the magnetite nanoparticles coated with 12% starch was evaluated on L929 cell lines using MTT assay. The analysis of FT-IR spectrum reveals a new bond at 810 cm-1 in the sample coated with 9 wt% starch, but this is not observed in other samples. The particle size of this sample is higher, whereas the lattice strain, coercivity (Hc) and saturation magnetization (Ms) are less compared with other samples. As the size decreases, the Ms, Hc and magnetic effective anisotropy Keff of these samples increase. The increase in Ms with particle size reduction may be attributed to magnetic anisotropy, grain boundary effects, and changes in surface anisotropy caused by surfactant variation.

Neutron diffraction studies on the full heusler alloy Co2FeGe

Abstract: Neutron diffraction studies have been carried on the polycrystalline sample Co2FeGe to investigate its structural and magnetic property. Earlier X-ray studies revealed that the system crystallizes in cubic L21 structure but detail investigation of anti-site disorder in this material is presented. The Rietveld refinement on the powder neutron diffraction was carried out using Full Prof method and the lattice parameter was observed to be 5.738 A and 5.729 A for RT and 5 K respectively. Further, magnetic structure analysis shows that the Co and Fe moments align ferromagnetically. The sub lattice moments were observed to be Co 1.67 μB and Fe 2.50 μB at room temperature where as at 5 K sublattice moments were observed to be Co 1.96 μB and Fe 2.56 μB.

Robust thermoelectric performance and high spin polarisation in CoMnTiAl and FeMnTiAl compounds

Abstract: New quaternary Heusler materials, CoMnTiAl and FeMnTiAl, have been investigated. These alloys are found to be stable in a ferromagnetic phase in Y1 type structure; the stability is also confirmed by various conditions of elastic constants. Both alloys show half-metallic (HM) ferromagnetic character with integer magnetic moments and they present a metallic nature. The values of the minority band gap in CoMnTiAl and FeMnTiAl are found to be 0.50 eV and 0.25 eV respectively. These alloys also possess excellent thermoelectric behaviour with Seebeck coefficients for CoMnTiAl (FeMnTiAl) as 31 μV K−1 (20 μV K−1) at room temperature. Here we report that CoMnTiAl achieves a figure of merit of 0.62 in a wide temperature range while FeMnTiAl achieves 0.77. Thus these new quaternary Heusler alloys can prove to be ultimate candidates for spin valves and for the best thermoelectric applicability over an ample temperature range.