Binod K. Rai

Synthesis of Hexagonal FeMnP Thin Films from a Single-Source Molecular Precursor

The first heterobimetallic phosphide thin film containing iron, manganese, and phosphorus, derived from the single-source precursor FeMn(CO)8 (μ-PH2 ), has been prepared using a home-built metal-organic chemical vapor deposition apparatus. The thin film contains the same ratio of iron, manganese, and phosphorus as the initial precursor. The film becomes oxidized when deposited on a quartz substrate, whereas the film deposited on an alumina substrate provides a more homogeneous product. Powder X-ray diffraction confirms the formation of a metastable, hexagonal FeMnP phase that was previously only observed at temperatures above 1200 °C. Selected area electron diffraction on single crystals isolated from the films was indexed to the hexagonal phase. The effective moment of the films (μeff =3.68 μB ) matches the previously reported theoretical value for the metastable hexagonal phase, whereas the more stable orthorhombic phase is known to be antiferromagnetic. These results not only demonstrate the successful synthesis of a bimetallic, ternary thin film from a single-source precursor, but also the first low temperature approach to the hexagonal phase of FeMnP.

The proof is in the powder: revealing structural peculiarities in the Yb3Rh4Sn13 structure type

Compounds adopting the Yb3Rh4Sn13 structure type have drawn attention because of the revelation of exotic states such as heavy fermion behavior, superconductivity, charge density wave, and quantum critical behavior. The prototypical structure has historically been modeled with a primitive cubic space group, Pmn; however, structural studies have led to the realization of disordered atomic sites, requiring lower symmetry models. We will review the low symmetry models required to describe the structural distortions in the related Yb3Rh4Sn13 structure type. In addition, we present the structure determination of a new analogue, Lu3Ir4Ge13, which adopts a new structural model in I41/amd.

Intermediate valence in single crystals of (Lu1−xY bx)3Rh4Ge13 (0 ≤ x ≤ 1)

Single crystals of (Lu1−xY bx)3Rh4Ge13 were characterized by magnetization, specific heat, and electrical resistivity measurements. Doping Yb into the non-magnetic Lu3Rh4Ge13 compound tunes this cubic system’s properties from a superconductor with disordered metal normal state (x < 0.05) to a Kondo for 0.05 ≤ x ≤0.2 and intermediate valence at the highest Yb concentrations. The evidence for intermediate Yb valence comes from a broad maximum in the magnetic susceptibility and X-ray photoelectron spectroscopy. Furthermore, the resistivity displays a local maximum at finite temperatures at intermediate compositions x, followed by apparent metallic behavior closest to the Yb end compound in the series.