S. K. Mohanta

Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

Employing the time differential perturbed angular distribution method, we have measured local susceptibility and spin relaxation rate of 54Fe nuclei implanted in III-V and II-VI semiconductors, CdTe, CdSe, and InSb. The magnetic response of Fe, identified to occupy the metal as well as the semi-metal atom sites, exhibit Curie-Weiss type susceptibility and Korringa like spin relaxation rate, revealing the existence of localized moments with small spin fluctuation temperature. The experimental results are supported by first principle electronic structure calculations performed within the frame work of density functional theory.

Observation of size dependent orbital magnetism of single Fe impurity in nanocrystalline Pb hosts

Employing the time differential perturbed angular distribution (TDPAD) technique we have investigated the local magnetism of single Fe impurity in nanocrystalline Pb matrices, by measuring the local susceptibility and spin relaxation rate of 54Fe nuclei. Compared to the nonmagnetic behavior of Fe in bulk Pb host, characterized by independent local susceptibility χloc(T), the magnetic response of Fe in the nanocrystalline samples with particle size of 10 nm and below exhibit Curie-Weiss like χloc(T) with positive slope, indicating the presence of large orbital magnetic moment on the Fe impurity. The orbital moment of Fe has been estimated to be ∼ 1 µB for 6 nm nano-Pb. Further investigations are being carried out to understand the emergence of orbital magnetism of Fe in nano-Pb.Employing the time differential perturbed angular distribution (TDPAD) technique we have investigated the local magnetism of single Fe impurity in nanocrystalline Pb matrices, by measuring the local susceptibility and spin relaxation rate of 54Fe nuclei. Compared to the nonmagnetic behavior of Fe in bulk Pb host, characterized by independent local susceptibility χloc(T), the magnetic response of Fe in the nanocrystalline samples with particle size of 10 nm and below exhibit Curie-Weiss like χloc(T) with positive slope, indicating the presence of large orbital magnetic moment on the Fe impurity. The orbital moment of Fe has been estimated to be ∼ 1 µB for 6 nm nano-Pb. Further investigations are being carried out to understand the emergence of orbital magnetism of Fe in nano-Pb.

Magnetic transition in CaFe2As2 studied via hyperfine field measurements for 66Ga by TDPAD technique

Employing the time differential perturbed angular distribution (TDPAD) method we have measured hyperfine field of 66Ga to study magnetic phase transition in CaFe2As2. The Bhf of 66Ga comes out to be positive having a magnitude of 16 kG at 15 K. Complimenting the earlier hyperfine interaction studies, our data confirms the first order magnetic transition at TN = 170K. The critical exponent obtained from our data, however, indicates quasi-two dimensional magnetic order, possibly due to canting of Fe moments away from the basal plane.

LOCAL MAGNETIC BEHAVIOR OF 54Fe in EuFe2As2 AND Eu0.5K0.5Fe2As2: MICROSCOPIC STUDY USING TIME DIFFERENTIAL PERTURBED ANGULAR DISTRIBUTION (TDPAD) SPECTROSCOPY

In this paper, we report the time differential perturbed angular distribution measurements of 54Fe on a polycrystalline EuFe2As2 and Eu0.5K0.5Fe2As2. The hyperfine field and nuclear spin-relaxation rate are strongly temperature dependent in the paramagnetic state suggesting strong spin fluctuation in the parent compound. The local susceptibility show Curie–Weiss-like temperature dependence and Korringa-like relaxation in the tetragonal phase indicating the presence of local moment. In the orthorhombic phase, the hyperfine field behavior suggesting quasi two-dimensional magnetic ordering. The experimental results are in a good agreement with first-principle calculations based on density functional theory.