Spin Glass Behavior of Isolated, Geometrically Frustrated Tetrahedra of Iron Atoms in the Intermetallic La₂₁Fe₈Sn₇C₁₂

Abstract

Metal flux synthesis in a low-melting eutectic mixture of lanthanum and nickel has produced a family of complex intermetallic carbide phases. La(21)Fe(8)M(7)C(12) (M = Sn, Bi, Sb, Te, Ge) has a new cubic structure featuring tetrahedra of iron atoms capped with carbon on each edge. These tetrahedra are surrounded by a La/M framework and are therefore isolated from each other. The antiferromagnetic coupling of the iron atoms is frustrated by their ideal tetrahedral arrangement; this is evidenced by magnetic susceptibility measurements on the La(21)Fe(8)Sn(7)C(12) analogue. Deviations from Curie-Weiss behavior begin at 100 K; variation in field-cooled vs zero-field-cooled behavior is seen at 5 K indicative of magnetic ordering. AC susceptibility data indicate that the temperature of this transition is frequency-dependent, behavior characteristic of spin glass systems.

Nanographene Magnetic Properties: A Monte Carlo Study

“…4 we present the variation of the hysteresis cycle for a very low temperature T = 0.05 K and a coupling constant J = −0.5 K. This sketch was observed in Ref. [22].…”

“…All these curves show divergence between the FC and ZFC data. Divergence between the FC and ZFC data in the nanographene sample is comparable to that in magnetically frustrated systems such as spin-glasses and superparamagnetic materials [21,22]. Application of high fields decreases the divergence between FC and ZFC data as is well outlined in Fig.…”

“…3. Some recent theoretical calculations and experiments predict the presence of antiferromagnetic states in the sheets and ferromagnetic states at the edges of graphene [22,23].…”

Orbital Dimer Model for the Spin-Glass State inY2Mo2O7Thygesen1, Paddison2, Zhang3 et al. 2017Phys. Rev. Lett.421510View full textAdd to dashboardCite

“…In canonical spin glasses-e.g., dilute magnetic alloys such as Cu 1−x Mn x [4] and site-disordered crystals such as Fe 2 TiO 5 [5]-the nature of structural disorder and its coupling to magnetism is well understood. However, spin-glass behaviour is also observed in well-ordered crystals where the geometry of the magnetic lattice alone can generate frustration (see, e.g., [6][7][8]). Here, the mechanism of spin-glass formation poses an important challenge for theory [9,10].…”

“…Second, the small displacement parameters of the Y and O2 sites indicate that they are not strongly disordered [ Fig. 1(c)]; we therefore fix the Y and O2 positions to their average values of (0, 8 ) and (0,0,0), respectively. Finally, the I4 1 md structure now allows for Mo displacements within the plane that contains the cubic local-111 axis (towards or away from the tetrahedron centre) and local-110 axis (towards or away from neighbouring Mo atoms lying on the same mirror plane).…”