Frustration-driven spin freezing in theS=12fcc perovskiteSr2

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

“…Integrating C mag /T up to the freezing temperature T f = 12 K yields an entropy of 0.18 J/K-mol Re. Although this value represents only 2% of the expected entropy release for an S = 1 spin glass, the drastically-reduced value is consistent with reports of spin glassiness in Sr 2 MgReO 6 (3% entropy release at T f ) [24], Li 4 MgReO 6 (14% entropy release below T f ) [37] and the jarosite (H 3 O)Fe 3 (SO 4 ) 2 (OH) 6 (6% entropy release at T f ) [38]. Furthermore, it is well-known that many spin glasses lose significant entropy above T f [39].…”

“…The low temperature data (T ≤ 20 K) fits well to the function C p = γT + βT 3 with γ = 15.0(1) mJ/K 2 -mol Re and β = 0.774(5) mJ/K 4 -mol Re. A non-zero γ is unexpected in insulators that exhibit magnetic order at low T , and this feature has been interpreted as a signature of spin glass behavior in insulating Sr 2 MgReO 6 [24] and Li 4 MgReO 6 [37]. Therefore, we assume that the linear component represents the magnetic contribution C mag .…”

“…On the other hand, the magnetic order of 4d 3 /5d 3 and 5d 5 systems often gives way to exotic magnetic states in 4d 1 /5d 1 quantum spin DPs. For example, Ba 2 YMoO 6 has been described as a valence bond glass with a collective spinsinglet ground state [21,22] and Sr 2 BReO 6 (B = Mg, Ca) are best characterized as unconventional spin glasses, since no obvious source of disorder has been found [23][24][25]. 5 analogues, and recent theoretical work has established a phase diagram for the cubic limit [26].…”

Frustration by competing interactions in the highly distorted double perovskites La2NaB′O6(Aczel1, Bugaris2, Li3 et al. 2013Phys. Rev. B554512View full textAdd to dashboardCite

“…Since the double perovskite structure type is very versatile with respect to chemical substitution and the B sites can accommodate a variety of transition metals, systematic studies can be performed to investigate the effects of changing the spin quantum number S and increasing the relativistic spin-orbit coupling by considering materials with 4d and 5d electrons. A series of exotic magnetic ground states have been observed previously in S = 1/2 and 1 systems, including a collective singlet state coexisting with paramagnetism in Ba 2 YMoO 6 [1,2] described as a valence bond glass [3], a collective singlet state in La 2 LiReO 6 [4], spin freezing without long-range order in Ba 2 YReO 6 [4], Sr 2 MgReO 6 [5] and Sr 2 CaReO 6 [6], shortrange order in La 2 LiMoO 6 [1], and a ferromagnetic (FM) Mott insulating state in Ba 2 NaOsO 6 [7,8]. Theoretical studies have also indicated that a wealth of other magnetic ground states are possible in these 4d and 5d quantum spin systems [9,10].…”

The role of nonmagnetic d0 vs. d10 B-type cations on the magnetic exchange interactions in osmium double perovskites

“…Double perovskite oxides, A 2 BB′O 6 , containing 4d/5d elements have attracted considerable attention due to their remarkable electronic and magnetic properties, such as room-temperature magnetoresistance [1], high-temperature ferrimagnetism [2,3], as well as spin glass [4] and valence bond glass behaviors [5]. As a characteristic structural feature, there are interpenetrating B and B′ face-centered cubic (fcc) sublattices, and their complex magnetic properties are determined by the intricate interplay between the geometrically frustrated intra-sublattice and inter-sublattices exchange interactions, which are correlated with structure distortions [6][7][8][9][10][11].…”