Magnetic structure ofNiS2−xSex

Abstract

NiS2−2xSex is revisited to determine the magnetic structure using neutron diffraction and magnetic representational analysis. Upon cooling, the insulating parent compound, NiS2, becomes antiferromagnetic with two successive magnetic transitions. The first transition (M1) occurs at TN ∼ 39 K with Γ1ψ 1 symmetry and magnetic propagation vector of k = (000). The second transition (M2) occurs at TN ∼ 30 K with k = (0.5, 0.5, 0.5) and a Γ1ψ 2 symmetry with face centered translations, giving rise to four possible magnetic domains. With doping, the system becomes metallic. The transition to the M2 state is suppressed prior to x = 0.4 while the M1 state persists. The M1 magnetic structure gradually vanishes by x ∼ 0.8, at a lower concentration than previously reported. The details of the magnetic structures are provided.

Quantum anomalous Hall effect and Anderson-Chern insulating regime in the noncollinear antiferromagnetic 3Q state

“…The emergence of the quantum phase of matter in frustrated quantum magnets has been the object of intense scrutiny in the past decades, with a particular focus on their magnetic phases and elementary excitations [45]. For the experimental realization of the QAH effect in antiferromagnets, magnetic pyrochlores [46] displaying an all-in, all-out spin configuration such as Pr 2 Ir 2 O 7 [47] and Nd 2 Ir 2 O 7 [48], possibly the Mott insulator NiS 2 [49,50], and layered triangular magnets such as cobaltites [51], in particular Na 0.5 CoO 2 [52], are considered as valuable candidates. All these materials exhibit a 3Q magnetic texture and insulating or bad-metal behavior and as such could support the QAH effect.…”

Thermoelectric properties, metal-insulator transition, and magnetism: Revisiting the Ni1−xCuxS2

“…[14] and references therein) for a d 7 band filling, whereas NiS2 is an insulating antiferromagnet with almost 1µB per Ni 2+ (d 8 ) (ref. [13,15,16]). Moreover, CuS2, due to the d 9 electronic configuration of divalent Cu, exhibits a metallic character and becomes a superconductor below Tc = 1.5 K [17].…”

“…Although most of the studies in line with the Mott-Hubbard scenario interpreted the effect of Co (or Cu) for Ni substitution in NiS2 as a way to remove (or add) electrons in the half-filled eg broad band [3][4][5], most recent ones pointed towards a possible charge disproportionation as the mechanism responsible for the insulating state [15]. The NiS2 magnetic behaviour is complex, with two different commensurate antiferromagnetic (AF) states, M1, below TN1 = 39.2 K, and M2, below TN2 = 29.75 K [15]. The existence of a weak ferromagnetic component, which sets in below TN2 and is thus associated to M2, can be observed by magnetic susceptibility measurements.…”

“…Its origin has long been debated since the pyrite cubic Pa3 " symmetry does not allow such a component. The coexistence of 4 different AF domains below TN1 could explain it, if one of these magnetic structures is slightly changed [15] (for instance by a stoichiometry deviation). Interestingly, as the Se for S substitution suppresses concomitantly the M2 phase and the insulating state, the presence of the weak ferromagnetic component related to M2 is taken as a signature of the insulating state [15].…”

“…The coexistence of 4 different AF domains below TN1 could explain it, if one of these magnetic structures is slightly changed [15] (for instance by a stoichiometry deviation). Interestingly, as the Se for S substitution suppresses concomitantly the M2 phase and the insulating state, the presence of the weak ferromagnetic component related to M2 is taken as a signature of the insulating state [15]. Apart from this charge ordering scenario, the low T transport properties have to be discussed with caution, as reports on NiS2 [18] and FeS2 [19,20] crystals of pyrite show that a surface layer with conducting states is responsible for apparent transitions in the T dependence of the electrical resistivity below ~ 150K.…”