Low-temperature specific heat for ferromagnetic and antiferromagnetic orders in CaRu_1−xMn_xO₃

Abstract

Low-temperature specific heat of CaRu1−xMnxO3 was measured to clarify the role of d electrons in ferromagnetic and antiferromagnetic orders observed above x = 0.2. Specific heat divided by temperature Cp/T is found to roughly follow a T 2 function, and relatively large magnitudes of electronic specific heat coefficient γ were obtained in wide x range. In particular, γ is unchanged from the value at x = 0 (84 mJ/K 2 mol) in the paramagnetic state for x ≤ 0.1, but linearly reduced with increasing x above x = 0.2. These features of γ strongly suggest that itinerant d electrons are tightly coupled with the evolution of magnetic orders in small and intermediate Mn concentrations.

Evolution of Ferromagnetic Clusters Originating from Itinerant Ru 4d Electrons in Sr1−xLaxRuO3

“…The fractions of the peak temperatures T * (1520 Hz)/T * (30 Hz) for x = 0.2 and 0.4 are estimated to be 1.004 and 1.13, respectively. [17]. As is suggested in the C p (T ) experiments in these compounds, we consider that the disappearance of anomaly in C p (T ) of the present system is related to the small entropy change associated with the FM transition, which is generated by the electrons with the itinerant characteristics, as well as the broadening of the onset induced by doping.…”

“…This may be also a reason for the increase in γ, but we consider that approximately threefold enhancement of the γ value seen in the small x range cannot be explained by such an effect only. In addition, it is interesting that the γ value at x = 0.4 is as large as that for the isostructural non-magnetic metal CaRuO 3 (∼ 82 mJ/K 2 mol) [17,18]. Considering the resemblance of the band structures between SrRuO 3 and CaRuO 3 [19], this agreement is reasonable on the assumption that the La ions in Sr 1−x La x RuO 3 hardly influence the band structure near the Fermi level and the valence of Ru ions, whereas they effectively weaken the FM correlation.…”