Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 19: Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter II

TT 19.8: Vortrag

Donnerstag, 27. März 2003, 16:15–16:30, HSZ301

The suppression of superconductivity in Mn-doped MgCNi₃ — •A. Das and R.K. Kremer — MPI fuer Festkoerperforschung, Stuttgart, Germany

The partial substitution of Ni with Mn in the recently discovered superconducting (T_C ∼8K for x = 0) compound, MgCNi_3−xMn_x, rapidly suppresses both the T_C and the superconducting volume fraction. Compounds with x ≥ 0.05 do not exhibit either superconductivity or long-range magnetic order down to 0.3K. The normal state χ follows a Curie-Weiss (CW) behavior. The effective moment/f.u. of MgCNi_3−xMn_x shows a maximum, 0.9µ_B for x=0.02 and decreases to 0.5µ_B for x = 0.05. This behavior is significantly different from that observed for Fe, Co, Cr, V and Cu substitution. EPR measurements indicate measurable signals only for x = 0.02 and 0.03 and the g values estimated are close to 2. The EPR lines have a typical metallic shape with the linewidth following a Korringa behavior. The study indicates a strong correlation between T_C and magnetic interactions in these compounds.