Signature of partially frustrated moments and a new magnetic phase in CeNiGe 2

Abstract

We report the magnetic, thermodynamic, and transport properties of a heavy fermion compound CeNiGe 2 . This compound undergoes two antiferromagnetic transitions around 4.1 and 3 K. It is observed in heat capacity that as magnetic field is increased to ~ 1 T, the two peak merge into a single peak around 3 K. However this peak is not suppressed under the application of magnetic field. Instead a new feature develops at 3.6 K above 1 T. The magnetic field induced new feature is investigated through entropy evolution, magnetic Gruneisen parameter and resistivity studies. These studies emphasis the fact that partial magnetic frustration due to field induced spin fluctuation is responsible for this observed feature. This partially frustrated regime develops a new antiferromagnetically ordered phase at high fields. In this compound magnetic field induced QCP is absent implying that the behavior of CeNiGe 2 is not in accordance to Doniach model proposed for heavy fermions compounds.

Observation of field induced anomalous quantum criticality in Ce0.6Y0.4NiGe2 compound

“…Figure 1 (a, b and c) shows the temperature response of DC susceptibility (M/H) under zero field cooling condition at different magnetic fields (0.5 -7 T) for Y-0.1, Y-0.2 and Y-0.4 compounds respectively. For Y-0.1 compound, a transition temperature ~ 3.3 K and a deviation ~2.2 K are observed which are shifted to lower temperature with increasing magnetic field and is suppressed below 1.8 K above 1 T. For the Y-0.2 compound, a transition temperature ~ 2.2 K is suppressed below 1.8 K at an applied field of 1 T whereas for the Y-0.4 compound, the transition temperature, for all values of the applied field, is below 1.8 K. This observation indicates that the antiferromagnetic ordering noted for CeNiGe 2 [19] get shifted down in temperature, with Ysubstitution. Inverse magnetic susceptibility is fitted with Curie-Weiss (CW) law (above 100 K) at 0.1 T under zero field cooling (ZFC) for all Y-substituted composition (not shown).…”

“…The maximum value of According to the relation, Γ mag = -(dS/dH)/C, where -dS/dH = -dM/dT; (-dM/dT)/T is related to Γ mag [16]. Hence the observed sign change in (-dM/dT)/T indicates to entropy accumulation and is related to magnetic frustration, as reported in CeNiGe 2 [19]. Hence, it can be said that magnetic frustration persists in the Y-0.1 compound.…”

“…Our investigation on CeNiGe 2 through Γ mag revealed that there is a sign change in Γ mag from positive to negative, which is related to magnetic frustration in this compound. This partially frustrated regime develops a new antiferromagnetically ordered phase at high fields and field induced QCP is absent in this compound [19]. Y-substitution at the Ce-site results in sequential suppression of magnetic ordering temperature below 1.8 K. However, Non-Fermi liquid behavior or zero field QCP is absent even after 40% replacement of Ce [20].…”

Evidence of partial gap opening and Ce-site dilution effects in a heavy fermion compound CeNiGe2

“…The heavy fermion compound CeNiGe 2 has been investigated in the last decade due to the intriguing physics exhibited by this compound [11][12][13][14][15]. Recent results indicate that external pressure and high magnetic field are incapable of repressing the magnetic ordering, resulting in the absence of Quantum critical point (QCP) and the behavior of this compound is not in accordance to the Doniach model, which is widely used to classify heavy fermion compounds [16,17]. Kim et al reported that partial replacement of Ge by Si results in suppression of magnetic ordering and some signatures of Quantum critical point (QCP) is observed [18].…”

“…Studies are carried out on the following compounds: CeNiGe 2 , Ce 0.9 Y 0.1 NiGe 2 , Ce 0.8 Y 0.2 NiGe 2 and Ce 0.6 Y 0.4 NiGe 2 . The parent compound reported undergoes two antiferromagnetic orderings around 4.1 and 3 K [11,12,17]. The fundamental observations are: i) with Y-substitution the two transition temperature decreases for Ce 0.9 Y 0.1 NiGe 2 while a single transition is observed for Ce 0.8 Y 0.2 NiGe 2 , ii) for Ce 0.6 Y 0.4 NiGe 2 compound the transition is suppressed below 1.8 K, iii) Arrott plots suggest the presence of SDW iv) non-linear susceptibility indicates magnetic instability which possibly leads to partial gap opening resulting in the observation of SDW v) zero field resistivity and heat capacity results also indicates to the presence of partially gap vi) with the increase in Y-substitution the gap opening is suppressed and also shifted down in temperature and vii) magnetic Gruneisen parameter gives an indication of presence of unusual fluctuations for Y-0.4 compound.…”