Reduced magnetic disorder at low temperature in Ca₃Co₂O₆ via zinc substitution

ABSTRACT

The compound Ca₃Co₂O₆ undergoes a transition into a spin-density wave (SDW) state near 24 K. Below ∼10 K, this unstable SDW state coexists with a nearly- degenerate commensurate antiferromagnetic state as well as short-range magnetic order. Clear signatures of this strong magnetic disorder have been observed in the response of entropy to changing magnetic field and temperature. We performed a calorimetry study of Ca₃Co₂O₆ and Ca₃Co_1.9Zn_0.1O₆ in order to compare their entropic responses at low temperature. Our results for Ca₃Co₂O₆ reveal that ΔS(T, H) ≡ S(T, H)−S(T, H = 0) increases as either temperature or magnetic field increase. In contrast, ΔS data for Ca₃Co_1.9Zn_0.1O₆ were relatively unresponsive to changes in temperature or field, suggesting that Zn substitution may reduce the low-temperature magnetic disorder observed in Ca₃Co₂O₆. These results are discussed within the context of two cases (Ca₃Co₂O₆ under applied pressure and Ca_2.75R_0.25Co₂O₆ (R = Dy, Lu)) in which a single magnetic ground state is stabilised.

KEYWORDS:

• Magnetic oxides
• magnetic phase transitions
• low-dimensional structures
• spin density wave
• specific heat
• magnetic disorder

Acknowledgements

XRD measurements were performed using the facilities, plus the scientific and technical assistance of the instrument staff at the M. J. Murdock Charitable Trust Multidisciplinary Research Laboratory, Central Washington University, USA, a facility partially funded by the M. J. Murdock Charitable Trust.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Research was supported by funding from the Central Washington University (CWU) Science Phase II Project, the CWU Office of Undergraduate Research, and start-up funds from CWU.