Jens Röder

CERN | CERN · Physics Department (PH)

Accurate nuclear quadrupole moment values are essential as benchmarks for nuclear structure models and for the interpretation of experimentally determined nuclear quadrupole interactions in terms of electronic and molecular structure. Here, we present a novel route to such data by combining perturbed γ-γ angular correlation measurements on free sma...

The common charge states of Sn are 2+ and 4+. While charge neutrality considerations favour 2+ to be the natural charge state of Sn in ZnO, there are several reports suggesting the 4+ state instead. In order to investigate the charge states, lattice sites, and the effect of the ion implantation process of dilute Sn atoms in ZnO, we have performed <...

Time Differential Perturbed Angular Correlation of γ-rays (TDPAC) experiments were performed for the first time in the decay of 68m Cu produced at the ISOLDE facility at CERN. Due to the short half-life of the source isotope, the measurements were carried out online. The intermediate state offers the unique opportunity to study the electromagnetic...

Nano-crystalline ZnO has been studied with perturbed angular correlation using 111mCd, implanted at ISOLDE/CERN and X-ray diffraction using Rietveld analysis. The data show a gradual increase in the crystal size and stress for a sample annealed at 600 °C, and reaching nearly properties of standard ZnO with tempering at 1000 °C. The perturbed angula...

The response of the structure of the M-type barium hexaferrite (BaFe12O19) to mechanical action through high-energy milling and its impact on the magnetic behaviour of the ferrite are investigated. Due to the ability of the 57Fe Mössbauer spectroscopic technique to probe the environment of the Fe nuclei, a valuable insight on a local atomic scale i...

The structural characterization of sol-gel based nano crystalline ZnO material is being reported as we observe several previously unreported structural aspects following a sequence of annealing stages. As-grown samples were characterised by Fourier Transform Infrared Spectroscopy (FTIR). Chemical purity of the nano-grains and their crystallinity ha...

Oxides of the chemical composition Bi 2(Fe xAl 1-x) 4O 9 (0.1 ≤ x ≤ 1) possessing a mullite-type structure have been investigated using 57Fe Mössbauer spectroscopy in the temperature range between room temperature and 1 073 K. The spectra have been fitted with two quadrupole doublets for Fe 3+ ions in octahedral and tetrahedral oxygen coordination....

We present a Raman spectroscopic investigation of the herbertsmithite ZnCu3(OH)6Cl2, a realization of a Heisenberg s=1/2 antiferromagnet on a perfect kagome lattice. Focusing on its magnetic excitation spectrum we find two components, a high-temperature quasielastic signal and a low temperature, broad maximum. The latter has a linear low-energy slo...

We present a Raman spectroscopic investigation of the Herbertsmithite ZnCu3(OH)6Cl2, the first realization of a Heisenberg s=1/2 antiferromagnet on a perfect kagome lattice. The magnetic excitation spectrum of this compound is dominated by two components, a high temperature quasi elastic signal and a low temperature, broad maximum. The latter has a...

A new generation time differential perturbed angular correlation (PAC) spectrometer has been designed and built. The design strategy and details of the data collection and reduction methodology are reported. First results obtained by the new spectrometer are reported and compared with PAC data obtained by more conventional means.

A comparison of high-resolution, angle-resolved photoemission spectroscopy (ARPES) data with ab initio band-structure calculations by density functional theory for the anticipated Kondo insulator FeSi shows that the experimental dispersions can quantitatively be described by an itinerant behavior provided that an appropriate self-energy correction...

In conventional perturbed angular correlation (PAC)-spectroscopy huge amounts of events are processed by fast electronics. Modern digital signal processing devices and the improvement in the computer technology in recent years allow today digital PAC-spectrometer setups capable to perform software-based data processing with all the benefits of stor...

High temperature measurements on Ln2NiO4+δ (Ln=La, Pr, Nd) have been performed indicating a complex behavior in PAC experiments which can be attributed to fluctuating electric field gradients caused by the high mobility of excess oxygen.KeywordsPerturbed angular correlation (PAC)La2NiO4 Pr2NiO4 Nd2NiO4 Hight temperature measurements

MAX-phases are hexagonal ternary carbides and nitrides with the general formula: M n + 1 AX n and n = 1 to 3. 111In was implanted into the two MAX compounds Ti2InC and Zr2InC. Based on the general knowledge of previous 111In implantations one expects to find the probes on the indium lattice-site in these compounds. First experiments on the anneal...

High temperature measurements on Ln2NiO4 + δ (Ln=La, Pr, Nd) have been performed indicating a complex behavior in PAC experiments which can be attributed to fluctuating electric field gradients caused by the high mobility of excess oxygen.