Study of Ni and Zn doped CeOFeAs: Effect on the structural transition and specific heat capacity

TL;DR

This study investigates how doping CeOFeAs with nonmagnetic Zn and magnetic Ni affects its structural transition and specific heat, revealing different impacts on the anomaly suppression and magnetic ordering.

Contribution

It provides new insights into how Zn and Ni doping differently influence the structural and magnetic properties of CeOFeAs, especially regarding transition temperatures and impurity effects.

Findings

Zn doping suppresses the structural anomaly to lower temperature (~130 K).

Ni doping does not affect the anomaly temperature and maintains metallic behavior.

Specific heat peaks related to Ce3+ ordering shift slightly with Zn doping, unaffected by Ni.

Abstract

We have systematically studied the substitution of nonmagnetic Zn and magnetic Ni at iron sites in Ce based oxypnictide. The parent compound (CeOFeAs) shows an anomaly in resistivity around 150 K due to structural transition from tetragonal (space group: P4/nmm) to orthorhombic structure (space group: Cmma). Substitution of Zn suppresses this anomaly to lower temperature (~130 K) but Ni substitution does not show any anomaly around this temperature and the compound behaves like a metal. Further, we find that non magnetic (Zn) doping leads to higher impurity scattering as compared to magnetic Ni doping. Similar to the resistivity measurement, the specific heat shows another jump near 4 K for CeOFeAs. This is attributed to the ordering of Ce3+ moments. This peak shifts to 3.8 K for Zn substituted compound and there is no change in the ordering temperature in the Ni substituted CeOFeAs. These peaks are broadened in applied magnetic field (5 T) and the calculated magnetic entropy tends to saturate at the same value for 0 T and 5 T external magnetic field.