Revisiting Goodenough-Kanamori rules in a new series of double perovskites LaSr1−xCaxNiReO6

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.

Intertwined magnetic sublattices in the double perovskite compound LaSrNiReO6

“…1(b) and 1(c)] before the μ + SR experiments. Starting with the χ (T ), two clear magnetic transitions are observed around T = 250 K and T = 25 K, which agree with previous reports [28,29]. An additional transition around T = 75 K is made clear in the zero-field-cooled (ZFC) configuration and its temperature derivative [inset of observed [see inset of Fig.…”

“…However, the ordered moments are sufficient to provide magnetic Bragg peaks (see Sec. IV), and their absences exclude a long-range magnetic order, which is in line with previous NPD measurements performed between T = 2 and 300 K [28,29]. Detailed NPD and magnetization analysis can be found in Refs.…”

“…Instead, an incommensurate long-range dynamically ordered ground state below T C = 23 K is proposed. Such state is still in line with previous neutron diffraction [28,29] and χ AC [28] results, as will be shown. Furthermore, between 23 K and 300 K, our μ + SR results distinguish three other magnetic regimes, including dense, dilute, and paramagnetic states.…”

“…[28] observed a frequency-dependent shift in the cusp of ac susceptibility, from where a spin glass ground state was suggested. Moreover, neutron diffraction studies indicated absence of long-range ordering [28,29], in line with a spin glass scenario. For the current sample, the absence of magnetic Bragg peaks in the neutron diffraction pattern are confirmed, as shown in Fig.…”

“…Detailed NPD and magnetization analysis can be found in Refs. [28,29]. In order to clarify the nature of the ambiguous ground state, μ + SR measurements were performed at selected temperatures.…”