Synthesis, structure, and magnetic properties of novel B-site ordered double perovskites, SrLaMReO₆ (M = Mg, Mn, Co and Ni)

Abstract

Four new double perovskites, SrLaMReO(6) (M = Mg, Mn, Co, Ni) in which Re(5+) (5d(2)) is present, were prepared via conventional solid state reactions and characterized by X-ray and neutron powder diffraction, XANES, SQUID magnetometry, and muon spin relaxation (μSR). Synchrotron X-ray and neutron diffraction experiments confirmed that all compounds crystallize in the monoclinic P2(1)/n structure type, which consists of alternately corner-shared octahedra of MO(6) and ReO(6). Rietveld refinement results indicated anti-site mixing of less than 7% on the M/Re sites. Bond valence sum calculations (BVS) suggest all M and Re ions are 2+ and 5+, respectively, and for the Mn-containing phase this is also supported by XANES measurements. All of the materials are paramagnetic at room-temperature and their Curie-Weiss temperatures are positive (except for Mg) indicating net ferromagnetic interactions. No evidence for long-range magnetic order is evident in the dc magnetic susceptibility and μSR measurements for SrLaMgReO(6) to 2 K. The Mn-phase shows long-range order at T(C) = 190 K and neutron diffraction revealed a ferromagnetic structure with a refined net moment of ∼3.7μ(B). Both Co- and Ni-containing phases exhibit spin glass behavior at T(G) = 23 and 30 K, respectively, which is supported by neutron diffraction and a.c. susceptibility data. The structure and physical properties of these four new rhenium based ordered double perovskites are compared to the closely related "pillared perovskites", La(5)Re(3)MO(16), the isoelectronic Os(6+) (5d(2)) double perovskite Sr(2)CoOsO(6), and the Re(6+) (5d(1)) double perovskites, Sr(2)MReO(6), (M = Mg, Ca, Mn, Co, Ni).

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.…”

“…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.…”

Structural and magnetic properties of the5d2double perovskitesSr2BReO6(Aczel1, Zhao2, Calder3 et al. 2016Phys. Rev. B233244View full textAdd to dashboardCite

“…7(a) are in good agreement with this interpretation, as the ZF relaxation at T = 7.5 K is significantly decoupled even in a modest applied LF of 0.002 T. Overall, the µSR data fully supports the picture of a singlet ground state coexisting with a small fraction of quasi-static free spins, suggested earlier on the basis of the χ measurements. We note that our µSR data for Sr 2 InReO 6 looks qualitatively similar to µSR data for other proposed singlet ground state DPs, including Ba 2 YMoO 6 [21,22] and SrLaMgReO 6 [30].…”

“…For example, a low-moment, long-range antiferromagnetic ground state has been reported for Ba 2 CaOsO 6 [27], spin freezing without signs of long-range magnetic order (i.e. spin glass) has been found for Ca 2 MgOsO 6 [28] and Ba 2 YReO 6 [29], and a non-magnetic singlet ground state was proposed for SrLaMgReO 6 [30]. There are also many other 5d…”