Madhusmita Baral

Observation of surface plasmon polaritons in 2D electron gas of surface electron accumulation in InN nanostructures

Recently, heavily doped semiconductors have been emerging as an alternative to low-loss plasmonic materials. InN, belonging to the group III nitrides, possesses the unique property of surface electron accumulation (SEA), which provides a 2D electron gas (2DEG) system. In this report, we demonstrated the surface plasmon properties of InN nanoparticles originating from SEA using the real-space mapping of the surface plasmon fields for the first time. The SEA is confirmed by Raman studies, which are further corroborated by photoluminescence and photoemission spectroscopic studies. The frequency of 2DEG corresponding to SEA is found to be in the THz region. The periodic fringes are observed in the near-field scanning optical microscopic images of InN nanostructures. The observed fringes are attributed to the interference of propagated and back-reflected surface plasmon polaritons (SPPs). The observation of SPPs is solely attributed to the 2DEG corresponding to the SEA of InN. In addition, a resonance kind of behavior with the enhancement of the near-field intensity is observed in the near-field images of InN nanostructures. Observation of SPPs indicates that InN with SEA can be a promising THz plasmonic material for light confinement.

Study of structural, magnetic and electronic properties of Ni-Fe-Ga based ferromagnetic shape memory alloys

The structural, magnetic and electronic properties of two samples with nominal compositions Ni50Fe20Ga30 (NFG-1) and Ni45Fe25Ga30 (NFG-2) have been studied. With increasing Fe substitution in place of Ni atoms, the valence electron concentration per unit cell (e/a) ratio decreased from 7.59 to 7.42. This decrease in e/a ratio results in increase Tc and saturation magnetization in NFG-2 compared to NFG-1. Photoelectron spectroscopy (PES) measurements have been carried out at 20 K and 300 K for both the samples. A comparison of the calculated (first principles) and the measured density of states (by PES) show that NFG-1 undergoes a martensite phase transition, whereas no such transition is observed for NFG-2.The structural, magnetic and electronic properties of two samples with nominal compositions Ni50Fe20Ga30 (NFG-1) and Ni45Fe25Ga30 (NFG-2) have been studied. With increasing Fe substitution in place of Ni atoms, the valence electron concentration per unit cell (e/a) ratio decreased from 7.59 to 7.42. This decrease in e/a ratio results in increase Tc and saturation magnetization in NFG-2 compared to NFG-1. Photoelectron spectroscopy (PES) measurements have been carried out at 20 K and 300 K for both the samples. A comparison of the calculated (first principles) and the measured density of states (by PES) show that NFG-1 undergoes a martensite phase transition, whereas no such transition is observed for NFG-2.

Electronic structure of Co-Ni-Ga Heusler alloys studied by resonant photoemission

The electronic structures of Co2.01Ni1.05Ga0.94 and Co1.76Ni1.46Ga0.78 Heusler alloys have been investigated by resonant photoemission spectroscopy across the 3p-3d transition of Co and Ni. For the Ni excess composition Co1.76Ni1.46Ga0.78, the valence band peak shows a shift of 0.25 eV as compared to the near stoichiometric composition Co2.01N11.05Ga0.94. Also an enhancement is observed in the Ni related satellite features in the valence band for the Ni excess composition. Due to hybridization of Co and Ni 3d states in these systems, the Co and Ni 3p-3d resonance energies are found to be higher as compared to Co and Ni metals. Theoretical first principle calculation is performed to understand the features in the valence band and the shape of the resonance profile.

Electronic structure of Co2MnSnHeusler alloy

The electronic structure of Co 2 MnSn Heusler alloy has been investigated by using resonant photoemission spectroscopy across the 3p-3d transition of Mn and Co. Angle dispersive X-ray diffraction pattern corroborates with the valence band photoemission spectra and confirms a conventional L21 structure for this system. In addition to Mn and Co 3p-3d transitions, the constant initial-state spectra shows two more features related to the multiplet structure of Mn and the small impurity phase of Co, which is confirmed by the diffraction data. Theoretical first principle calculation is performed to understand the features in the valence band and the shape of the resonance profile.

Electronic structure of Co[sub 2]MnSn Heusler alloy

The electronic structure of Co 2 MnSn Heusler alloy has been investigated by using resonant photoemission spectroscopy across the 3p-3d transition of Mn and Co. Angle dispersive X-ray diffraction pattern corroborates with the valence band photoemission spectra and confirms a conventional L21 structure for this system. In addition to Mn and Co 3p-3d transitions, the constant initial-state spectra shows two more features related to the multiplet structure of Mn and the small impurity phase of Co, which is confirmed by the diffraction data. Theoretical first principle calculation is performed to understand the features in the valence band and the shape of the resonance profile.

Electronic structure of Co2MnSn Heusler alloy

The electronic structure of Co 2 MnSn Heusler alloy has been investigated by using resonant photoemission spectroscopy across the 3p-3d transition of Mn and Co. Angle dispersive X-ray diffraction pattern corroborates with the valence band photoemission spectra and confirms a conventional L21 structure for this system. In addition to Mn and Co 3p-3d transitions, the constant initial-state spectra shows two more features related to the multiplet structure of Mn and the small impurity phase of Co, which is confirmed by the diffraction data. Theoretical first principle calculation is performed to understand the features in the valence band and the shape of the resonance profile.