Colossal magnetoresistance in a nonsymmorphic antiferromagnetic insulator

Abstract

Here we investigate antiferromagnetic Eu5In2Sb6, a nonsymmorphic Zintl phase. Our electrical transport data show that Eu5In2Sb6 is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which is consistent with the presence of magnetic polarons. From ab initio calculations, the paramagnetic state of Eu5In2Sb6 is a topologically nontrivial semimetal within the generalized gradient approximation (GGA), whereas an insulating state with trivial topological indices is obtained using a modified Becke−Johnson potential. Notably, GGA + U calculations suggest that the antiferromagnetic phase of Eu5In2Sb6 may host an axion insulating state. Our results provide important feedback for theories of topological classification and highlight the potential of realizing clean magnetic narrow-gap semiconductors in Zintl materials.

Field-induced metal-to-insulator transition and colossal anisotropic magnetoresistance in a nearly Dirac material EuMnSb2

“…The large negative MR response sets in when the magnetic moments of Eu 2+ form AFM order, and disappears quickly above T N , indicating a clear correspondence between the negative MR and magnetic order of Eu sublattice. Previously, negative MR has been observed in some low-carrier-density magnetic Eu-based materials [45][46][47][48] . The negative MR was ascribed to the formation of magnetic polaron, for example, in Eu 5 In 2 Sb 6 47 and EuB 6 48 .…”

“…Previously, negative MR has been observed in some low-carrier-density magnetic Eu-based materials [45][46][47][48] . The negative MR was ascribed to the formation of magnetic polaron, for example, in Eu 5 In 2 Sb 6 47 and EuB 6 48 . Nevertheless, ac magnetic susceptibility measurement in EuMnSb 2 43 does not support the existence of magnetic polaron, which excludes the magnetic polaron as possible origin of the negative MR.…”

Robust narrow-gap semiconducting behavior in square-net La$_{3}$Cd$_{2}$As$_{6}$

“…This tendency occurs for two reasons. First, the R-square net p-bands close to the Fermi level (E F ) and the M d bands become well separated, which allows electron transfer and the formation of anionic units, that form covalent bonds leading to Zintl phases [14][15][16][17] . Second, there is greater mixing between s and p orbitals in pnictide elements with small atomic number (Z), which (again) favors the classic octet rule in a distorted structure over hypervalent bonds in an undistorted square net 18,19 .…”

Narrow-gap semiconducting behavior in antiferromagnetic Eu$_{11}$InSb$_9$

“…Zintl compounds are valence precise, and electron transfer between cations and anions is expected to create a semiconducting state [7]. Further, the inclusion of rare-earth elements with localized f electrons may enable magnetic order and reduce sensitivity to air and moisture compared to their alkaline and alkaline-earth analogues [8][9][10].…”

“…For example, Eu 5 In 2 Sb 6 and Yb 5 In 2 Sb 6 are narrow-gap semiconductors that satisfy the Zintl formalism and show promise as thermoelectric materials [10,15]. Eu 5 In 2 Sb 6 also undergoes a dramatic reduction in electrical resistance in the presence of magnetic fields [8]. This property, initially observed in perovskite manganites, is coined colossal magnetoresistance (CMR) [16] and has been attributed to the presence of magnetic polarons, i.e., quasiparticles arising from strong exchange coupling between free carriers and background spins of divalent europium.…”