Specific heat and magnetic susceptibility measurements of YBa2Cu4O8 a study of the density of electronic states

Abstract

Abstract Specific heat and magnetic susceptibility measurements are reported for polycrystalline bulk samples of YBa 2 Cu 4 O 8 and DyBa 2 Cu 4 O 8 prepared at high oxygen pressure and for a companion sample of YBa 2 Cu 3 O 7 . The magnitude of the idealized specific heat jump ΔC p / T at T c (=80±0.5 K ) is 16±2 mJ /(mol K 2 ) and the transition width Δ T c is about 3 K for YBa 2 Cu 4 O 8 . The corresponding values for DyBa 2 Cu 4 O 8 are 75 K, 15±2 mJ/(mol K 2 ) and 3.3 K. The size of these jumps is greatly reduced compared to YBa 2 Cu 3 O 7 . The normal state spin susceptibility of YBa 2 Cu 4 O 8 is calculated to be only about 15% smaller than in YBa 2 Cu 3 O 7 , and it is temperature dependent. Both these results are consistent with a smaller electronic density of states for YBa 2 Cu 4 O 8 .