Revisiting Goodenough-Kanamori rules in a new series of double perovskites LaSr1\u2212xCaxNiReO6

Somnath Jana,Payel Aich,Vasudeva Siruguri,O K Forslund,Y Sassa,M Månsson,Sugata Ray,Peter Svedlindh,P Anil Kumar,Olof Karis,V Pomjakushin,E Nocerino

doi:10.1038/s41598-019-54427-0

Abstract

The magnetic ground states in highly ordered double perovskites LaSr1−xCaxNiReO6 (x = 0.0, 0.5, 1.0) are studied in view of the Goodenough-Kanamori rules of superexchange interactions in this paper. In LaSrNiReO6, Ni and Re sublattices are found to exhibit curious magnetic states separately, but no long range magnetic ordering is achieved. The magnetic transition at ~255 K is identified with the independent Re sublattice magnetic ordering. Interestingly, the sublattice interactions are tuned by modifying the Ni-O-Re bond angles through Ca doping. Upon Ca doping, the Ni and Re sublattices start to display a ferrimagnetically ordered state at low temperature. The neutron powder diffraction data reveals long range ferrimagnetic ordering of the Ni and Re magnetic sublattices along the crystallographic b-axis. The transition temperature of the ferrimagnetic phase increases monotonically with increasing Ca concentration.

Highlights

Double perovskites (DP; A2BB′ O6)[1,2,3] belong to a class of materials which exhibit many interesting properties and rich physics
Another interesting possibility appears in DPs, when both B and B′ ions are magnetic, but the valence electrons of B ion lack the orbital symmetry of the same of B′ ion for effective B-O-B′ super-exchange interaction
With Ca doping, the structure undergoes into larger monoclinic distortion, which results in a larger deviation of the Ni-O-representation of Ni (Re) (∠NOR) bond angles from 180°

Summary

Introduction

Double perovskites (DP; A2BB′ O6)[1,2,3] belong to a class of materials which exhibit many interesting properties and rich physics. All the samples appeared to be single phased as no impurity peak is detected in the whole 2θ range in the powder XRD data, collected at room temperature for LaSr1−xCaxNiReO6 (LSCNRO) series (see Fig. 2(a,b)).

Results

Conclusion