Observation of a Griffiths-like Phase in the Magnetocaloric CompoundTb5Si2Ge2

Abstract

The onset of a Griffiths-like phase has been observed in Tb5Si2Ge2 (TC=110 K) by means of magnetic susceptibility and small-angle neutron scattering experiments. We show the growth of a ferromagnetic cluster system characterized by an inverse susceptibility exponent lower than unity at TC<T<TG approximately 200 K. We suggest that the Griffiths-like state is originated by local disorder within the crystallographic structure, stabilized and enhanced by competing intralayer and interlayer magnetic interactions. Both factors thus promote segregation of nanometric regions with ferromagnetic interactions.

Griffiths-like phase and magnetic correlations at high fields in Gd5Ge4

“…[28][29][30] The suppression of the anomaly in χ by h dc [ Fig. 3(a)] without any trace of energy absorption or dissipation at about h dc ≈ 200 Oe suggests that the mechanism underlying the formation of the GL phase is actually suppressed as the field is increased rather than just hidden by the PM background, as previously suggested for Tb 5 Si 2 Ge 2 .…”

“…3(a)] without any trace of energy absorption or dissipation at about h dc ≈ 200 Oe suggests that the mechanism underlying the formation of the GL phase is actually suppressed as the field is increased rather than just hidden by the PM background, as previously suggested for Tb 5 Si 2 Ge 2 . 30 A comprehensive data set of (χ ) −1 in the temperature range T N -T G was fitted to the predicted temperature dependence of the susceptibility for a GL phase in f -electron compounds, χ −1 ∝ (T − T c ) (1−λ) , 31 where T c denotes the critical temperature and (1 − λ) is the effective index with 0 λ < 1. The simultaneous fit of T c and λ converges to a Curie-Weiss law (λ = 0).…”

Magnetic anomalies in the spin-chain compoundSr3CuRhO6: Griffiths-phase-like behavior of magnetic susceptibility

“…Viewed together with the shape of M(H) curve at 7 K (see figure 2b), these observations imply that (ferro)magnetic components are present in the material, the magnetization of which can be gradually saturated with increasing fields. The features reveal as though the linear response of the paramagnetic component gets gradually highlighted with increasing H. It may be recalled that the observed H-dependence of χ -1 (T) plots, seen in figure 3, is the fingerprint [6,7] of Griffiths phase.…”

“…Negligibly small values of M IRM at t= 0 mentioned earlier implies that globally there is no spontaneous magnetization as expected for Griffiths phase. It is known [6][7][8][9]14] that the χ in the Griffiths phase is characterized by an exponent lower than unity, i.e., χ -1 (T) α (T-T o ) 1-λ (0<λ<1). Therefore, we have fitted logarithm of χ -1 in the range 6 to 10 K, say for H= 20 Oe data, and the value of λ turns to be 0.8 (see figure 3, inset), in agreement with theoretical predictions [14], whereas in the range 12-20 K, it is close to zero.…”

“…The intra-cluster magnetic ordering temperature above experimentally observable bulk T C varies depending on the size of the cluster and therefore there is a spectrum of T C below the characteristic Griffiths temperature, T G . Though the existence of such a magnetic phase due to quenched disorder has been discussed in connection with giant magnetoresistance behavior of manganites [6,[11][12][13], non-Fermi liquid behavior in f-electron systems [14,15], and dilute magnetic semiconductors [16] as well as for a Tb-based intermetallic compound [7], it is believed that the experimental evidence in favor of the existence of Griffiths phase is still inadequate [17].…”