MAGNETIC-PROPERTIES, MOSSBAUER MEASUREMENTS, AND SPECIFIC-HEAT STUDIES OF LA2MCU2O6 (M = CA OR SR) COMPOUNDS

Magnetic-susceptibility powder-x-ray-diffraction Mossbauer studies on Fe-57-doped samples an specific-heat measurements were used to study t he magnetic nature of La2MCu2O6 and La1.6Sr0.4CaCu2O6 materials. The f ivefold pyramidal coordination of the double CUO2 planes is similar to that of the Cu(2) site in YBa2Cu3Oz 6 < z < 7. All the compounds stud ied are not superconducting and order antiferromagnetically at T(N) = 10-20 K, which is extremely low as compared with T(N) = 420 K, obtaine d for nonsuperconducting YBa2CuO3. The presence of Fe does not affect T(N). The specific-heat curves do not show any anomaly at T(N), and th e electronic specific-heat coefficient is around 4 mJ/mol K2.