Low-temperature heat capacities of the clathrate salts Ag7O8NO3 and Ag7O8HF2

Thermodynamic properties of the clathrate-type silver-oxide Ag6O8AgHF2

“…For X ¼ NO À 3 , BF À 4 , and HF À 2 , superconductivity was already reported in the 1960s with critical temperatures T c = 1.0 K, 0.15 K, and 1.0-1.5 K, respectively [1][2][3]. For other family members with X = HSO 4 , HCO 3 , or in more general for M = Tl or Hg, Ag 6 O 8 TlClO 4 , and Ag 6 O 8 HgClO 4 , only the synthesizing methods and crystal-structure analyses have been reported so far [4][5][6][7].…”

“…From this fit, we deduced the following values for the Sommerfeld coefficient c and the coefficient of the phononic contribution b:c = 55.5 mJ/mol K 2 and b = 1.3 mJ/mol K 4 . Conway et al [3] reported that their specific-heat data in an applied magnetic DC field H = 2400Oe > H c2 includes a term proportional to T À2 explained by the assumption of paramagnetic impurities contained in their samples. Neither a T À2 nor any different term is needed to yield a reasonable description of our data measured in H = 3000 Oe.…”

“…However, the specific-heat data in Ref. [3] exhibit a very broad superconducting transition. The authors explained this broadness due to paramagnetic impurities contained in their samples.…”

Superconducting State of Silver-Oxide Clathrate Ag6O8AgNO3

“…If one chooses M = Ag, several family members are reported to be superconducting: [7][8][9][10] For other family members with X = HSO 4 , HCO 3 , or in more general for M = Tl or Hg, Ag 6 O 8 TlClO 4 , and Ag 6 O 8 HgClO 4 , only the methods of synthesizing methods and analyzing crystal structures have been reported thus far. 7,[11][12][13] There are two early publications dealing with Ag 6 O 8 -AgNO 3 : ref.…”

“…The thermodynamic critical field H c was estimated to be 130 Oe. 10) Despite these early publications, we reinvestigated the physical properties of Ag 6 O 8 AgNO 3 because there are no systematic studies of the normal and superconducting properties available thus far, e.g., neither the H-T phase diagram nor the normal-state specific heat is known.…”