2008/03/04 by H. Alloul, I. R. Mukhamedshin, G. Collin +1
Materials Science · Physics and Astronomy · #Heusler alloys: electronic and magnetic properties #Magnetic and transport properties of perovskites and related materials #Thermal Expansion and Ionic Conductivity #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1209/0295-5075/82/17002
published as Europhysics Letters v.82 p.17002 (2008)
openalex publication_date 2008/03/04 · arxiv created 2008/03/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We have synthesized and characterized four different stable phases of Na ordered Na x CoO 2 , for 0.65< x <0.8. Above 100 K they display similar Curie-Weiss susceptibilities as well as ferromagnetic q =0 spin fluctuations in the CoO 2 planes revealed by 23 Na NMR data. In all phases from 59 Co NMR data we display evidences that the Co disproportionate already above 300 K into non-magnetic Co 3+ and magnetic ≈Co 3.5+ sites on which holes delocalize. This allows us to understand that metallic magnetism is favored for these large Na contents. Below 100 K the phases differentiate, and a magnetic order sets in only for x ≳0.75 at T N =22 K. We suggest that the charge order also governs the low- T energy scales and transverse couplings.