Architecture of nanoscale ferroelectric domains in GaMo₄S₈

Abstract

Local-probe imaging of the ferroelectric domain structure and auxiliary bulk pyroelectric measurements were conducted at low temperatures with the aim to clarify the essential aspects of the orbitally driven phase transition in GaMo 4 S 8 , a lacunar spinel crystal that can be viewed as a spin-hole analogue of its GaV 4 S 8 counterpart. We employed multiple scanning probe techniques combined with symmetry and mechanical compatibility analysis to uncover the hierarchical domain structures, developing on the 10-100 nm scale. The identified domain architecture involves a plethora of ferroelectric domain boundaries and junctions, including primary and secondary domain walls in both electrically neutral and charged configurations, and topological line defects transforming neutral secondary walls into two oppositely charged ones.

Orbital-order driven ferroelectricity and dipolar relaxation dynamics in multiferroic GaMo4S8

“…The obtained values are of the same order of magnitude as P deduced from pyrocurrent measurements reported in Ref. [15]. Figure S2 shows the temperature dependence of the dielectric constant ' at various frequencies, measured with two types of electrode material, namely sputtered gold (lines) and silver paint (symbols).…”

“…Multiferroic GaMo 4 S 8 To further corroborate the recently reported ferroelectricity in GaMo 4 S 8 below the Jahn-Teller (JT) transition [15], here we present so-called positive-up-negative-down (PUND) measurements (Fig. S1).…”

Macroscopic manifestation of domain-wall magnetism and magnetoelectric effect in a Néel-type skyrmion host

“…In these compounds, four polar domain states with polarizations along the cubic 〈111〉-type axes can exist. The different types of domains, with a typical width of 10-1000 nm, naturally form lamellar patterns with {100}-type neutral DWs, as observed in GaV 4 S 8 18 and GaMo 4 S 8 48 . To characterize the polar domains and to estimate the density of DWs in GaV 4 Se 8 , we combined several complementary scanning probe microscopy techniques, including non-contact atomic force microscopy (nc-AFM), scanning dissipation microscopy (SDM), and frequency-modulated Kelvin-probe force microscopy (KPFM).…”

“…Besides the high DW density, another peculiarity of this polar phase is the lack of 180°DWs and the presence of 109°DWs only, a consequence of the non-centrosymmetric cubic phase 18,48 . (This is in contrast to perovskite ferroelectrics, where the paraelectric cubic phase is centrosymmetric.)…”

Possible emergence of a skyrmion phase in ferroelectric GaMo4S8

“…[22] and 47 K in Ref. [23], driven by the cooperative Jahn-Teller distortion. At high temperatures, the structure is noncentrosymmetric and nonpolar with the Td point group, i.e.…”