Revisiting Goodenough-Kanamori rules in a new series of double perovskites LaSr$_{1-x}$Ca$_x$NiReO$_6$

TL;DR

This study investigates how chemical doping in double perovskites affects magnetic interactions and ordering, revealing tunable ferrimagnetic states and the relevance of Goodenough-Kanamori rules in these materials.

Contribution

It demonstrates how Ca doping modifies magnetic sublattice interactions and induces ferrimagnetic order in LaSr$_{1-x}$Ca$_x$NiReO$_6$, expanding understanding of superexchange in these compounds.

Findings

Ni and Re sublattices show no long-range order in LaSrNiReO$_6$.

Ca doping induces ferrimagnetic order at low temperatures.

Transition temperature increases with Ca concentration.

Abstract

The magnetic ground state in highly ordered double perovskites LaSr$_{1-x}$Ca$_x$NiReO$_6$ ($x$ = 0.0, 0.5, 1.0) were studied in view of the Goodenough-Kanamori rules of superexchange interactions. In LaSrNiReO$_6$, Ni and Re sublattices are found to exhibit curious magnetic states, but do not show any long range magnetic ordering. The magnetic transition at $\sim$ 255 K is identified with the Re sublattic magnetic ordering. The sublattice interactions are tuned by modifying the Ni-O-Re bond angles via changing the lattice structure 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 reveals a canted alignment between the Ni and the Re sublattices, while the individual sublattice is ferromagnetic. The transition temperature of the ferrimagnetic phase increases monotonically with increasing Ca concentration.