Specific Heat of (Ca1-xSrx)3Ru2O7 Single Crystals

TL;DR

This study measures the specific heat of (Ca1-xSrx)3Ru2O7 crystals, analyzing phase transitions and how Sr substitution affects their thermodynamic properties, revealing insights into magnetic and structural phase behaviors.

Contribution

It provides detailed calorimetric data on phase transitions in (Ca1-xSrx)3Ru2O7, highlighting the nature of the Neel and structural transitions and their evolution with Sr doping.

Findings

The Neel transition shows a mean-field-like step with a large magnitude.

The structural transition's entropy decreases rapidly with Sr substitution.

The latent heat suggests a broadened first-order transition.

Abstract

We have measured the specific heat of crystals of (Ca1-xSrx)3Ru2O7 using ac- and relaxation-time calorimetry. Special emphasis was placed on the characterization of the Neel (TN=56 K) and structural (Tc = 48 K) phase transitions in the pure, x=0 material. While the latter is believed to be first order, detailed measurements under different experimental conditions suggest that all the latent heat (with L ~ 0.3 R) is being captured in a broadened peak in the effective heat capacity. The specific heat has a mean-field-like step at TN, but its magntitude (Delta cP ~ R) is too large to be associated with a conventional itinerant electron (e.g. spin-density-wave) antiferromagnetic transition, while its entropy is too small to be associated with full ordering of localized spins. The TN transition broadens with Sr substitution while its magnitude decreases slowly. On the other hand, the entropy change associated with the Tc transition decreases rapidly with Sr substitution and is not observable for our x=0.58 sample.