H. S. Mund

Investigation of orbital magnetization in inverse spinel cobalt ferrite using magnetic Compton scattering

We present the spin momentum densities of CoFe2O4 measured at 8 and 300 K using magnetic Compton scattering. The magnetic Compton profiles were decomposed into component profiles of constituents namely Fe and Co, to determine their role in the formation of total spin moment. It is seen that the major contribution (about 80%) in the spin moment is from Co, whereas the itinerant electrons show a small reverse polarization. Moreover, it is clearly visualized that the spin moment at Co reduces from 2.55 → 2.35 μB/f.u. while going from 8 → 300 K. The magnetic Compton profiles, when compared with the magnetization data, show about 17% contribution of orbital moment to the total magnetic moment at both temperatures. The origin of the orbital moment is explained on the basis of rotation of hole on t2g orbital of Co+2 ion.

Magnetic and electrical behavior of Al doped La0.7Ca0.3MnO3 manganites

The effects of doping on magnetic and electrical transport mechanism of polycrystalline samples La0.7Ca0.3Mn1−xAlxO3 (x=0,0.02,0.04,0.06,0.08,0.1) have been investigated. Magnetization data reveal that long-range ferromagnetic ordering persists in all samples and the saturation moment decreases linearly as x increases. Resistivity data have been fitted with the variable range hopping model to estimate the density of state at Fermi level. It was observed that the substitution of Al in the series leads to a decrease in conductivity of the doped manganites samples, with conduction being controlled by the disorder induced localization of charge carriers.

Enhancement of ferromagnetism in Ni excess Cu1−xNixMnSb half Heusler alloys

Spin momentum densities of Cu1−xNixMnSb (for x = 0.17 and 0.22), derived from experimental magnetic Compton profiles (MCPs), show an increase in magnetic moment while going from x = 0.17 → 0.22, which is attributed to Mn 3d states. MCPs along with magnetization data suggest a negligible contribution of orbital moment. The MCPs and spin moments at Mn 3d states computed using the spin polarized relativistic Korringa-Kohn-Rostoker technique are in good agreement with the experimental data. An unusual increase in magnetic moment (2.77 ± 0.03 μB/f.u. for x = 0.17 to 3.94 ± 0.03 μB/f.u. for x = 0.22) is due to significant rise in local magnetic moment on Mn site. For x = 0.22 (0.17), presence of antiferromagnetic phase is observed to be 2 (31)%.

On the role of Al doping in La0.7Ca0.3MnO3: A magnetic Compton scattering study

Spin and orbital magnetic moments in hole doped manganite La0.7Ca0.3Mn1−xAlxO3 (x = 0, 0.02, and 0.06) have been scrutinized using experimental spin momentum densities. An analysis of magnetic Compton profiles shows that the spin moment of Mn 3d has a major contribution towards the total spin moment and its contribution decreases as we increase the concentration of Al. The present experiment along with magnetization data predict orbital moment of −0.29 ± 0.03 μB/f.u. in the parent compound (x = 0), which almost disappears on substitution of Al. The results are explained on the basis of imbalance in Mn3+ and Mn4+ charge ratio in these compounds.

Study of spin and orbital magnetization in Dy- and Gd-doped Co ferrite using magnetic Compton scattering

Temperature dependent experimental magnetic Compton profiles (MCPs) of inverse spinel CoFe2−xRExO4 (x = 0.05; RE = Dy, Gd) have been decomposed into constituent profiles to determine site-specific spin moments. A comparison of MCPs of doped and undoped CoFe2O4 shows a decrease in spin moment on 5% doping of Dy and Gd. Reduction in spin moment is explained on the basis of migration of Co2+ ions from octahedral to tetrahedral sites, which is also supported by photoelectron spectroscopy measurements. The orbital moments deduced from combination of spin momentum density and magnetization data are found to be almost similar in doped ferrites.

Evaluation of orbital moment in Ni-Zn ferrites: A magnetic Compton scattering study

Temperature dependent magnetic Compton profiles of Ni1−xZnxFe2O4 (x = 0.0, 0.1, 0.2) ferrites have been decomposed into component profiles to determine the site-specific magnetic moments. For a quantitative evaluation of orbital moment, the spin momentum density data have been combined with magnetization data. Interestingly, the orbital magnetic moment decreases from 0.25 ± 0.03 μB/f.u. (for x = 0.0) to 0.09 ± 0.03 μB/f.u. (for x = 0.2) which is in contrast to spin moment. A decrease in ratio of orbital to spin moments in Ni rich ferrites is explained on the basis of spin-orbit coupling and crystal field interaction.

A magnetic Compton scattering study of Ga rich Co–Ni–Ga ferromagnetic shape memory alloys

The temperature dependent spin momentum densities of Co(1.8)NiGa(1.2) and Co(2)Ni(0.76)Ga(1.24) alloys have been measured using the magnetic Compton scattering technique. The individual contributions of constituents in the formation of the total spin moment are also calculated using Compton line shape analysis. The magnetic Compton data when compared with the magnetization data obtained using a vibrating sample magnetometer show a negligible orbital contribution. The spin moments deduced from the experimental Compton data are compared with the theoretical results obtained from the full potential linearized augmented plane wave method and are found to be in good agreement. The origin of the magnetism in both alloys is also described in terms of the e(g) and t(2g) contributions of Ni and Co.

Electronic structure of CaCO3: A Compton scattering study

In the present work, we have studied electron momentum density of CaCO₃ using a Compton scattering technique. The experiment has been performed using a 100 mCi (241)Am (59.54 keV) Compton spectrometer. The experimental data have been interpreted in terms of theoretical Compton profiles. To compute the theoretical momentum densities, energy bands and density of states, we have used linear combination of atomic orbitals method as embodied in CRYSTAL09 code. We have used local density approximation, generalized gradient approximation (GGA) and second order GGA (SOGGA) within the frame work of density functional theory. It is seen that the GGA gives a better agreement with the experimental data than other approximations. We have also discussed the energy bands and density of states of CaCO₃.

Electronic Structure and Magnetic Properties of Ni2MnSn Heusler Alloy

The spin dependent momentum densities in Ni 2 MnSn Heusler alloy have been measured at 10 and 300 K using magnetic Compton scattering. For these measurements, we have used 182.79 keV circularly polarized synchrotron radiation at SPring8, Japan. Spin dependent electron momentum densities are analyzed in terms of Mn 3d, Ni 3d and itinerant electrons to calculate their role in formation of net spin moment. Magnetic moments at different sites of constituent atoms have also been compared with the present full potential linearised augmented plane wave calculations and other available data.

Electronic structure of FeTiSb using relativistic and scalar-relativistic approaches

Electronic and magnetic properties of FeTiSb have been reported. The calculations are performed using spin polarized relativistic Korringa-Kohn-Rostoker scheme based on Green’s function method. Within SPR-KKR a fully relativistic and scalar-relativistic approaches have been used to investigate electronic structure of FeTiSb. Energy bands, total and partial density of states, atom specific magnetic moment along with total moment of FeTiSb alloys are presented.